The EG&G FX-6A xenon flashtube is used in the General radio Strobotac,
which is used to measure the speed of machines rotating at up to 25,000
rpm.

The FX-6As darken with age, and are hard to find.

FX-6A is an old EG&G product. The relevant part of EG&G was sold to
Perkin-Elmer (http://optoelectronics.perkinelmer.com), and P-E now makes
these flashlamps. I think that this is still done in Salem, Mass.

I talked to P-E today. The FX-6A is available for US $232.00 each for 1
to 10 units. FX-6 series are called "low cost strobes"; I don't want to
know what normal and high cost means.

They also sent me a FX-6A datasheet (well, max operating conditions):

Max energy per flash: 5 Joules.

Max average power: 7 watts.

Max anode voltage: 1000 Vdc.

Min anode voltage: 300 Vdc. (Typical will be ~600 Vdc.)

Max flash rate: 500 flashes per second (30,000 rpm).

Arc length is 7.9 mm. The trigger electrode (called the "sparker" is
near to the anode and cathode, inside the glass envelope. The required
voltage and energy was not documented.

Joe Gwinn

"Joseph Gwinn" wrote: (clip) The FX-6A is available for US $232.00 each
for 1 to 10 units. (clip)
^^^^^^^^^^^^^^^^
Holy crap! I have an old Strobotac that I bought years ago for $5 (I
think.) Care to make me an offer?

According to Joseph Gwinn :
The EG&G FX-6A xenon flashtube is used in the General radio Strobotac,
which is used to measure the speed of machines rotating at up to 25,000
rpm.

The FX-6As darken with age, and are hard to find.

FX-6A is an old EG&G product. The relevant part of EG&G was sold to
Perkin-Elmer (http://optoelectronics.perkinelmer.com), and P-E now makes
these flashlamps. I think that this is still done in Salem, Mass.

Hmm ... where my wife was born (though not in the P-E plant. :-)

I talked to P-E today. The FX-6A is available for US $232.00 each for 1
to 10 units. FX-6 series are called "low cost strobes"; I don't want to
know what normal and high cost means.

####### ###
# # # # #### # # ###
# # # # # # # # ###
# # # # # ###### #
# # # # # # #
# # # # # # # # ###
####### #### #### # # ###

(The above should be viewed with a fixed-pitch font like Courier. If
you don't want to take the time to switch fonts, it simply says "Ouch!"
in *big* letters. :-)

That means that the batch of four which I won on an eBay auction
is worth $928.00.

They were made May 22 1975 according to the stamp on the box
endflap.

They also sent me a FX-6A datasheet (well, max operating conditions):

Max energy per flash: 5 Joules.

Max average power: 7 watts.

Max anode voltage: 1000 Vdc.

Min anode voltage: 300 Vdc. (Typical will be ~600 Vdc.)

Max flash rate: 500 flashes per second (30,000 rpm).

O.K. Which probably determines the choice of max RPM on the
Strobotac.

Arc length is 7.9 mm. The trigger electrode (called the "sparker" is
near to the anode and cathode, inside the glass envelope.

Actually -- there are five of them, One (pin 1) is very close to
one electrode (pin 9), and the remaining ones are equally spaced, with
the final one not being nearly as close to its electrode.

But this suggests that they fire at much lower voltages than the
typical trigger wrapped around the outside of the typical flashlamp.

The required
voltage and energy was not documented.

Hmm ... A pity that it is not documented. That could be one of
the factors which would make a normal flashlamp not suitable for the
circuit in the Strobotac.

Thanks for digging up this information.

If nothing else, it makes me feel better about spending a bit
over $125.00 for the batch of four of them -- and now I understand the
motivation of the winning bidder in the batch which I *lost* prior to
that. :-)

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Joseph Gwinn wrote:
The EG&G FX-6A xenon flashtube is used in the General radio Strobotac,
which is used to measure the speed of machines rotating at up to 25,000
rpm.

The FX-6As darken with age, and are hard to find.



Thats an outrageous price! - depending on the mechanical fittings, it
SHOULD be possible to use a "standard" flash tube (their about $5 here)
- you would need to get a trigger transformer and add a wire wrapped
around the body to trigger them, but hey.....worth a try - might be
other considerations, would need to dig out the data sheets and see.

Andrew VK3BFA.

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

On 18 Apr 2006 02:29:55 -0700, "Andrew VK3BFA"
wrote:

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

Looks like the ones used for dance-floor lighting- have you tried a
stage equipment shop?

-Carl

In article ,
"Leo Lichtman" wrote:

"Joseph Gwinn" wrote: (clip) The FX-6A is available for US $232.00 each
for 1 to 10 units. (clip)
^^^^^^^^^^^^^^^^
Holy crap! I have an old Strobotac that I bought years ago for $5 (I
think.) Care to make me an offer?

Ten dollars?

If I get a Strobotac, I'll be real motivated to do the engineering to
find and/or fit a substitute flashtube.

Joe Gwinn

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
The EG&G FX-6A xenon flashtube is used in the General radio Strobotac,
which is used to measure the speed of machines rotating at up to 25,000
rpm.

The FX-6As darken with age, and are hard to find.

FX-6A is an old EG&G product. The relevant part of EG&G was sold to
Perkin-Elmer (http://optoelectronics.perkinelmer.com), and P-E now makes
these flashlamps. I think that this is still done in Salem, Mass.

Hmm ... where my wife was born (though not in the P-E plant. :-)

I talked to P-E today. The FX-6A is available for US $232.00 each for 1
to 10 units. FX-6 series are called "low cost strobes"; I don't want to
know what normal and high cost means.

####### ###
# # # # #### # # ###
# # # # # # # # ###
# # # # # ###### #
# # # # # # #
# # # # # # # # ###
####### #### #### # # ###

(The above should be viewed with a fixed-pitch font like Courier. If
you don't want to take the time to switch fonts, it simply says "Ouch!"
in *big* letters. :-)

That means that the batch of four which I won on an eBay auction
is worth $928.00.

They were made May 22 1975 according to the stamp on the box
endflap.

I wonder if P-E is actually making the tubes these days, or selling new
old stock one tube at a time.

I also wonder if the Russians have duplicated the FX-6A. They still
make pretty good vacuum tubes, and I would not be surprised if there was
a Soviet-era copy of the Strobotac.


They also sent me a FX-6A datasheet (well, max operating conditions):

Max energy per flash: 5 Joules.

Max average power: 7 watts.

Max anode voltage: 1000 Vdc.

Min anode voltage: 300 Vdc. (Typical will be ~600 Vdc.)

Max flash rate: 500 flashes per second (30,000 rpm).

O.K. Which probably determines the choice of max RPM on the
Strobotac.

Yes.


Arc length is 7.9 mm. The trigger electrode (called the "sparker" is
near to the anode and cathode, inside the glass envelope.

Actually -- there are five of them, One (pin 1) is very close to
one electrode (pin 9), and the remaining ones are equally spaced, with
the final one not being nearly as close to its electrode.

Apparently, all but the one designated as the sparker are used only as
probes. No idea what is being probed for, or why.

Pin# - Use
1-3 - probe when required
4 - Anode (ie, positive)
5 - open
6 - probe when required
7 - Probe (no "when required")
8 - Sparker (will most likely be positive wrt the cathode)
9 - Cathode (ie, negative)


But this suggests that they fire at much lower voltages than the
typical trigger wrapped around the outside of the typical flashlamp.

Yes, by a factor. The current Series 1100 tubes should give us the
needed voltage range range, although the 1100s only go to 300 Hz.


The required voltage and energy was not documented.

Hmm ... A pity that it is not documented. That could be one of
the factors which would make a normal flashlamp not suitable for the
circuit in the Strobotac.

One clue is that the max anode voltage is 1,000 volts. The sparker
voltage will be in that range, as the sparker is simply another nearby
electrode, albeit one not designed to handle the full flash energy.
Typically, an internal trigger takes less than the full holdoff voltage.

I recall that the flash capacitors are charged to 600 volts; don't know
where I got that tidbit.

A little reverse engineering is in order. Can you measure the trigger
capacitor voltage and capacitance in your Strobotac? This will tell us
the needed trigger energy.

Does anyone have a circuit diagram?


Thanks for digging up this information.

If nothing else, it makes me feel better about spending a bit
over $125.00 for the batch of four of them -- and now I understand the
motivation of the winning bidder in the batch which I *lost* prior to
that. :-)

Yes.

I do see some current-production P-E flashlamps rated for 1,000 Hz, so
some kind of retrofit seems possible, although one may also need to
either replace or augment the trigger transformer.

Joe Gwinn

In article .com,
"Andrew VK3BFA" wrote:

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

Thanks. Who is the maker? Do they have application notes and more
complete datasheets?

Joe Gwinn

In article ,
Carl Byrns wrote:

On 18 Apr 2006 02:29:55 -0700, "Andrew VK3BFA"
wrote:

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

Looks like the ones used for dance-floor lighting- have you tried a
stage equipment shop?

I would have thought dance-floor strobes would be far slower and far
more powerful than a Strobotac.

One use of the FX-6A that I've found is automotive wheel balancers that
were made by Balance Technology Inc (BTI) and competitors. Wonder what
they use these days; I'm sure that won't stand still for $230 per tube.

Joe Gwinn

Joseph Gwinn wrote:
In article .com,
"Andrew VK3BFA" wrote:

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

Thanks. Who is the maker? Do they have application notes and more
complete datasheets?

Joe Gwinn

Hi Joe,
what you see is what you get - the data sheet was all that was on a
local retailers website. probably, asuming your in the US, that Digikey
or Mouser would have similar ones - perhaps they would have more data.
The max strobe rate - no idea, but I cant imagine that the listed tube
in the original post is the ONLY one suitable in the world.

Its a basis for experimentation - might work, might not, Relatively
cheap and easy to lash up - if it works, a nice bit of test gear back
on the road, if it doesnt - well, youve blown 10 bucks and a bit of
time..... Trigger transformers are also available, about 2 dollars.

I am a working technicain, not an engineer - cant give you voluminous
theory on the application, I use the "suck it and see"
approach........sometimes works, sometimes a spectacular failure. But I
do get enough oddball electronic things like this working to make a
(precarious) living.......the high value or rare device thats worth
putting a few hours of experimentation into before they go to the
dumpster....

Andrew VK3BFA.

"Joseph Gwinn" wrote in message
...
In article ,
Carl Byrns wrote:

On 18 Apr 2006 02:29:55 -0700, "Andrew VK3BFA"
wrote:

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

Looks like the ones used for dance-floor lighting- have you tried a
stage equipment shop?

I would have thought dance-floor strobes would be far slower and far
more powerful than a Strobotac.

One use of the FX-6A that I've found is automotive wheel balancers that
were made by Balance Technology Inc (BTI) and competitors. Wonder what
they use these days; I'm sure that won't stand still for $230 per tube.


Anyone try uaing one of the new super bright white LEDs for a strobe?

According to Andrew VK3BFA :

Joseph Gwinn wrote:
In article .com,
"Andrew VK3BFA" wrote:

http://www.jaycar.com.au/products_uploaded/SL2692.pdf

is a link to the typical tube I was talking about.

[ ... ]

what you see is what you get - the data sheet was all that was on a
local retailers website. probably, asuming your in the US, that Digikey
or Mouser would have similar ones - perhaps they would have more data.
The max strobe rate - no idea, but I cant imagine that the listed tube
in the original post is the ONLY one suitable in the world.

There is also the FX-7 -- which appears to have a larger
envelope size, but otherwise be similar, so it might work, except for
not fitting the reflector. And I'll bet that it is at least as
expensive as the FX-6A.

Its a basis for experimentation - might work, might not, Relatively
cheap and easy to lash up - if it works, a nice bit of test gear back
on the road, if it doesnt - well, youve blown 10 bucks and a bit of
time..... Trigger transformers are also available, about 2 dollars.

Yes -- but these are quite unlike the FX-6A.

The FX-6A is in a stubby 9-pin miniature tube base.

It has the two main electrodes allocated to two of those pins.

It has *five* *internal* trigger electrodes connected to five of
the remaining pins -- fine wires reaching in to points along the arc
path, and all electrically independent.

The Strobotac has a 7-conductor ribbon cable going from the
electronics box to the pivoted stem which contains the 9-pin socket for
the flash tube, and over which the neck of the reflector fits. (This
rather limits the maximum dimensions of the tube to ones no larger in
some dimension than the diameter of a 9-pin miniature tube.

The reflector is designed so the arc length (about 1/2" long) is
in the focus of the reflector.

The internal flash triggers operate (presumably) at a much lower
voltage than external triggers.

The fact that a separate wire is brought out to each suggests
that each has a unique voltage applied to direct the arc along the
intended path.

I am a working technicain, not an engineer - cant give you voluminous
theory on the application, I use the "suck it and see"
approach........sometimes works, sometimes a spectacular failure.

Including possibly an induced failure to the trigger circuits in
the StroboTac in this case.

While I have the four remaining unused lamps, plus the one in
pretty good condition, and one rather darkened from use, I intend to use
it as it was designed.

If those ever are all expended -- *then* I will try retrofitting
some newer flashlamp. But I think that not too many of those are
designed to survive 27K flashes/minute. :-) And I'm not sure about the
trigger transformer, either.

O.K. You finally got my interest piqued sufficiently, so I just
pulled it out of its case:

1) It is old enough to be tube driven, not solid state. A 5965
and a 5727. This suggests that the trigger circuit is not as
fragile as I at first feared.

2) Looking at the ribbon cable end inside the box, the flashlamp
main terminals are the end-most ribbon cable leads, the only
trigger connection is for the center one, feeding the centermost
trigger electrode which suggests that the ribbon cable acts as a
capacitive voltage divider to couple signal to the remaining
trigger electrodes.

3) The trigger transformer is a potted brick, about
1-1/2 x 2-1/4 x 3/4"

4) The main capacitor for the highest flash level is 1.15 uF at
1000 VDC. The smallest is 0.47 uF, also at 1000 VDC. The
middle one is 0.22 uF, again at 1000 VDC. They are all marked
"Vicofilm Capacitor" from "Industrial Condenser Company".

5) It does have *some* solid state devices -- a bridge of top-hat
rectifiers. :-)

6) There is also a three-section electrolytic. 50 uF, 25 uF, and
25 uF at 450VDC.

7) The speed pot is one of General Radio's special precision wirewound
pots, though there are four Allen-Bradley sealed pots scattered
around the rest of the circuit.

8) And, of course, it has a custom power transformer, with no
useful markings.

9) Two slow-blow (MDL) fuses (1/2 A, 250V) in clips on one of the
circuit boards.

10) One NE-2 lamp between two upright braces, secured by a
heat-shrink band as a vibration seal. It is presumably a
voltage reference, as there is no way for the light to get out,
and the pilot light for the speed scales is a bayonet-base
incandescent pilot light. (Another NE-2 is used as part of the
calibration system -- it is visible through a window in the
front panel, and you set the speed pot to specific speeds, and
tune the front-accesible pots for lowest brighten/dim rate in
the lamp.

11) The date codes on components seem to be in the 1967-1968 range.

Don't expect me to attempt to trace the circuit -- it is General
Radio's quality construction of the period, with single-sided circuit
boards, but it is too dense a construction for me to bother without
serious need.

But I
do get enough oddball electronic things like this working to make a
(precarious) living.......the high value or rare device thats worth
putting a few hours of experimentation into before they go to the
dumpster....

Understood. But at present, it is cheaper to buy more
StroboTacs on eBay than to buy new lamps. So -- as long as the lamps
with those are in good shape, you could get one, sell the lamp back on
eBay, and experiment with your own StroboTac.

FWIW -- the energy per flash is in three ranges, corresponding
to three flash rate ranges, so you don't overheat the lamp and burn it
out too rapidly.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

They were made May 22 1975 according to the stamp on the box
endflap.

I wonder if P-E is actually making the tubes these days, or selling new
old stock one tube at a time.

A good question. I wonder whether they have re-boxed them if
selling NOS -- or whether the boxes still say EG&G? :-)

I also wonder if the Russians have duplicated the FX-6A. They still
make pretty good vacuum tubes, and I would not be surprised if there was
a Soviet-era copy of the Strobotac.

That is possible.

They also sent me a FX-6A datasheet (well, max operating conditions):

Max energy per flash: 5 Joules.

Max average power: 7 watts.

Max anode voltage: 1000 Vdc.

Min anode voltage: 300 Vdc. (Typical will be ~600 Vdc.)

Max flash rate: 500 flashes per second (30,000 rpm).

O.K. Which probably determines the choice of max RPM on the
Strobotac.

Yes.


Arc length is 7.9 mm. The trigger electrode (called the "sparker" is
near to the anode and cathode, inside the glass envelope.

Actually -- there are five of them, One (pin 1) is very close to
one electrode (pin 9), and the remaining ones are equally spaced, with
the final one not being nearly as close to its electrode.

Apparently, all but the one designated as the sparker are used only as
probes. No idea what is being probed for, or why.

Pin# - Use
1-3 - probe when required
4 - Anode (ie, positive)
5 - open
6 - probe when required
7 - Probe (no "when required")
8 - Sparker (will most likely be positive wrt the cathode)
9 - Cathode (ie, negative)

O.K. My examination of the device shows that only one is
actually driven directly -- but the others appear to be capacitively
coupled through the ribbon cable. I haven't pulled the lamp socket out,
but based on the layout of the ribbon cable, I would expect the
"sparker" to be the middle of the set.

But this suggests that they fire at much lower voltages than the
typical trigger wrapped around the outside of the typical flashlamp.

Yes, by a factor. The current Series 1100 tubes should give us the
needed voltage range range, although the 1100s only go to 300 Hz.

O.K. Good for slow rotating devices -- but not the top end.

The required voltage and energy was not documented.

Hmm ... A pity that it is not documented. That could be one of
the factors which would make a normal flashlamp not suitable for the
circuit in the Strobotac.

One clue is that the max anode voltage is 1,000 volts. The sparker
voltage will be in that range, as the sparker is simply another nearby
electrode, albeit one not designed to handle the full flash energy.
Typically, an internal trigger takes less than the full holdoff voltage.

I recall that the flash capacitors are charged to 600 volts; don't know
where I got that tidbit.

Hmm ... the three main flash capacitors in the StroboTac are all
rated at 1000 VDC -- and selected by the range switch.

A little reverse engineering is in order. Can you measure the trigger
capacitor voltage and capacitance in your Strobotac? This will tell us
the needed trigger energy.

It is pretty densely packed. The trigger transformer seems to
be in a potted brick -- and I *think* that the capacitor is included in
that brick.

Does anyone have a circuit diagram?

Not I. One of the things that I looked for while I had it open
was a circuit diagram pasted inside the case. No such luck.

O.K. A google Search lead me to a PDF file of a manual for the
1538-A Strobotac -- as slightly later version.

This says that the tube operates at 800-1000 VDC, and the
trigger is 5000 V.

O.K. I've found some schematics -- and this one is solid-state,
while the previous one (which I have) is tube based -- as shown by
another posting this evening on this newsgroup -- so I won't duplicate
it here.

Go to

http://www.ietlabs.com/pdf/Manuals/

and you will find manuals for both the 1538-A and the 1531-A/B, among
others.

I've just bookmarked that -- and gotten manuals for several
things which I have.

[ ... ]

I do see some current-production P-E flashlamps rated for 1,000 Hz, so
some kind of retrofit seems possible, although one may also need to
either replace or augment the trigger transformer.

O.K. Good luck with those.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

DoN. Nichols wrote:
According to Andrew VK3BFA :

Joseph Gwinn wrote:
In article .com,
"Andrew VK3BFA" wrote:


Understood. But at present, it is cheaper to buy more
StroboTacs on eBay than to buy new lamps. So -- as long as the lamps
with those are in good shape, you could get one, sell the lamp back on
eBay, and experiment with your own StroboTac.


Don,
fairly obviously, if you have spares there is no point in trying to fit
a substitute. QED.
I wonder what the modern equivalent is - probably hand held, LCD
readout, and runs forever on 2 by AA cells......a white LED?

BTW - this old gear is interesting from a "antique electronics"
viewpoint - I have a shed full of NIXIE based test equip. I will oneday
get some of it working, - no point except getting it going.. and if I
dont, the kids can curse me as they cart it off to the dump when I
die.. ( a 5 digit nixie tube based precision voltmeter is not much use
for anything except as a prop in sci-fi movies - see "The Dish" movie
if it made it your way, a whole rack full of HP counters on self
test...)


Andrew VK3BFA.

Here is something useful

http://members.misty.com/don/samflash.html



Regards,

Boris Mohar

Got Knock? - see:
Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

void _-void-_ in the obvious place

Tm wrote:



Anyone try uaing one of the new super bright white LEDs for a strobe?


Somehow I doubt you could get a short enough flash to be
practical and I wonder about the max rep rate.
Intrested in the results if any one ever tries it.
...lew...

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:


Arc length is 7.9 mm. The trigger electrode (called the "sparker" is
near to the anode and cathode, inside the glass envelope.

Actually -- there are five of them, One (pin 1) is very close to
one electrode (pin 9), and the remaining ones are equally spaced, with
the final one not being nearly as close to its electrode.

Apparently, all but the one designated as the sparker are used only as
probes. No idea what is being probed for, or why.

Pin# - Use
1-3 - probe when required
4 - Anode (ie, positive)
5 - open
6 - probe when required
7 - Probe (no "when required")
8 - Sparker (will most likely be positive wrt the cathode)
9 - Cathode (ie, negative)

O.K. My examination of the device shows that only one is
actually driven directly -- but the others appear to be capacitively
coupled through the ribbon cable. I haven't pulled the lamp socket out,
but based on the layout of the ribbon cable, I would expect the
"sparker" to be the middle of the set.

The circuit drawings seem to say that all are driven by a 5 KV pulse
through 22 picofarad capacitors, one per line.


But this suggests that they fire at much lower voltages than the
typical trigger wrapped around the outside of the typical flashlamp.

Yes, by a factor. The current Series 1100 tubes should give us the
needed voltage range range, although the 1100s only go to 300 Hz.

O.K. Good for slow rotating devices -- but not the top end.

The required voltage and energy was not documented.

Hmm ... A pity that it is not documented. That could be one of
the factors which would make a normal flashlamp not suitable for the
circuit in the Strobotac.

One clue is that the max anode voltage is 1,000 volts. The sparker
voltage will be in that range, as the sparker is simply another nearby
electrode, albeit one not designed to handle the full flash energy.
Typically, an internal trigger takes less than the full holdoff voltage.

I recall that the flash capacitors are charged to 600 volts; don't know
where I got that tidbit.

Hmm ... the three main flash capacitors in the StroboTac are all
rated at 1000 VDC -- and selected by the range switch.

It may be 800 volts. It seems to depend on the model. It's easy to
achieve 600 volts with a voltage quadrupler, without a HV transformer.


A little reverse engineering is in order. Can you measure the trigger
capacitor voltage and capacitance in your Strobotac? This will tell us
the needed trigger energy.

It is pretty densely packed. The trigger transformer seems to
be in a potted brick -- and I *think* that the capacitor is included in
that brick.

It is, according to the circuit diagrams.


Does anyone have a circuit diagram?

Not I. One of the things that I looked for while I had it open
was a circuit diagram pasted inside the case. No such luck.

O.K. A google Search lead me to a PDF file of a manual for the
1538-A Strobotac -- as slightly later version.

This says that the tube operates at 800-1000 VDC, and the
trigger is 5000 V.

O.K. I've found some schematics -- and this one is solid-state,
while the previous one (which I have) is tube based -- as shown by
another posting this evening on this newsgroup -- so I won't duplicate
it here.

Go to

http://www.ietlabs.com/pdf/Manuals/

and you will find manuals for both the 1538-A and the 1531-A/B, among
others.

I've just bookmarked that -- and gotten manuals for several
things which I have.

Bingo! Of course. I got them. Thanks.


I do see some current-production P-E flashlamps rated for 1,000 Hz, so
some kind of retrofit seems possible, although one may also need to
either replace or augment the trigger transformer.

O.K. Good luck with those.

I may also have a way to make an ordinary flashtube work far above it's
normal flash rate, based on tricks used to get far above 25,000 plashes
per minute.

Joe Gwinn

In article ,
says...
Tm wrote:



Anyone try uaing one of the new super bright white LEDs for a strobe?


Somehow I doubt you could get a short enough flash to be
practical and I wonder about the max rep rate.
Intrested in the results if any one ever tries it.
...lew...

I don't know about white LEDs, but some of the small high speed (30
KRPM) winders I've been involved with use red LEDs as built-in strobes,
but not very bright.

LED arrays with sub-millisecond flash duration for high speed machine
vision illumination are common. The LEDs are driven hard to get
brightness, so duty cycle is relatively low.

Like this:
http://www.advancedillumination.com/category/AL.html

Ned Simmons

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Apparently, all but the one designated as the sparker are used only as
probes. No idea what is being probed for, or why.

Pin# - Use
1-3 - probe when required
4 - Anode (ie, positive)
5 - open
6 - probe when required
7 - Probe (no "when required")
8 - Sparker (will most likely be positive wrt the cathode)
9 - Cathode (ie, negative)

And based on the manuals (discussed below) pins 1, 4, and 9 are
actually used. (1 being one of the "probes", 4 being the anode, and 9
being the cathode). All other "probes" are only getting signal
capacitively coupled by the adjacent runs in the ribbon cable (perhaps
1-1/2" long).

O.K. My examination of the device shows that only one is
actually driven directly -- but the others appear to be capacitively
coupled through the ribbon cable. I haven't pulled the lamp socket out,
but based on the layout of the ribbon cable, I would expect the
"sparker" to be the middle of the set.

The circuit drawings seem to say that all are driven by a 5 KV pulse
through 22 picofarad capacitors, one per line.

If so, the "capacitors" are in reality parasitic capacitance
in that ribbon cable, as only the one is actually connected to anything,
at least on my 1531-A. The photo (Figure 4-10, page 26) in the manual
for the 1538-A shows the same construction, FWIW.

[ ... ]

One clue is that the max anode voltage is 1,000 volts. The sparker
voltage will be in that range, as the sparker is simply another nearby
electrode, albeit one not designed to handle the full flash energy.
Typically, an internal trigger takes less than the full holdoff voltage.

I recall that the flash capacitors are charged to 600 volts; don't know
where I got that tidbit.

Hmm ... the three main flash capacitors in the StroboTac are all
rated at 1000 VDC -- and selected by the range switch.

It may be 800 volts. It seems to depend on the model. It's easy to
achieve 600 volts with a voltage quadrupler, without a HV transformer.

Looking at the full schematic for the 1531-A, The anode and
cathode are respectively connected to +400V and -400V (developed from a
310V winding on the power transformer in the 1531-A), and in the 1538-A,
there appears to be a one-shot triggering the primary of a small
transformer as a DC-DC converter, which gives +800V.

I don't find complete schematics for the 1538-A, though the
1531-A has the complete set. Both have the ghost views of the PC
traces. And, apparently, IET still services (and supplies parts) for
both models.

I wonder how much of GR's line IET took over? Or was it just a
case of renaming the company for whatever reason?

[ ... ]

It is pretty densely packed. The trigger transformer seems to
be in a potted brick -- and I *think* that the capacitor is included in
that brick.

It is, according to the circuit diagrams.

Making it rather difficult to check out.

Does anyone have a circuit diagram?

[ ... ]

O.K. I've found some schematics -- and this one is solid-state,
while the previous one (which I have) is tube based -- as shown by
another posting this evening on this newsgroup -- so I won't duplicate
it here.

Go to

http://www.ietlabs.com/pdf/Manuals/

and you will find manuals for both the 1538-A and the 1531-A/B, among
others.

I've just bookmarked that -- and gotten manuals for several
things which I have.

Bingo! Of course. I got them. Thanks.

Great!


I do see some current-production P-E flashlamps rated for 1,000 Hz, so
some kind of retrofit seems possible, although one may also need to
either replace or augment the trigger transformer.

O.K. Good luck with those.

I may also have a way to make an ordinary flashtube work far above it's
normal flash rate, based on tricks used to get far above 25,000 plashes
per minute.

I see that the FX-7A is suggested as the current replacement
lamp. I wonder what the prices are for that one?

Enjoy
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"Ned Simmons" wrote in message
...
In article ,
says...
Tm wrote:



Anyone try uaing one of the new super bright white LEDs for a strobe?


Somehow I doubt you could get a short enough flash to be
practical and I wonder about the max rep rate.
Intrested in the results if any one ever tries it.
...lew...

I don't know about white LEDs, but some of the small high speed (30
KRPM) winders I've been involved with use red LEDs as built-in strobes,
but not very bright.

LED arrays with sub-millisecond flash duration for high speed machine
vision illumination are common. The LEDs are driven hard to get
brightness, so duty cycle is relatively low.

Like this:
http://www.advancedillumination.com/category/AL.html


You could get white light from three (RGB) LEDs and have the high speed.
It could even have many LEDs to get the desired brightness.

Tom

You would need a uP scanner with a program for delay and dwell between and on each diode.
That or buy perfect spectral set of eye sensitivity level.

So not so easy but doable.

Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Tm wrote:
"Ned Simmons" wrote in message
...

In article ,
says...

Tm wrote:



Anyone try uaing one of the new super bright white LEDs for a strobe?


Somehow I doubt you could get a short enough flash to be
practical and I wonder about the max rep rate.
Intrested in the results if any one ever tries it.
...lew...

I don't know about white LEDs, but some of the small high speed (30
KRPM) winders I've been involved with use red LEDs as built-in strobes,
but not very bright.

LED arrays with sub-millisecond flash duration for high speed machine
vision illumination are common. The LEDs are driven hard to get
brightness, so duty cycle is relatively low.

Like this:
http://www.advancedillumination.com/category/AL.html



You could get white light from three (RGB) LEDs and have the high speed.
It could even have many LEDs to get the desired brightness.

Tom



----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Why would it need to be perfect? I would think close to white would be fine.
You could just use the correct number of red, green, and blue LEDs and
current drive them. You could even dump a cap into them with a SCR or power
mos device to get high peak power. A processor could do the display and
timing.

T


"Martin H. Eastburn" wrote in message
...
You would need a uP scanner with a program for delay and dwell between and
on each diode.
That or buy perfect spectral set of eye sensitivity level.

So not so easy but doable.

Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Tm wrote:
"Ned Simmons" wrote in message
...

In article ,
says...

Tm wrote:



Anyone try uaing one of the new super bright white LEDs for a strobe?


Somehow I doubt you could get a short enough flash to be
practical and I wonder about the max rep rate.
Intrested in the results if any one ever tries it.
...lew...

I don't know about white LEDs, but some of the small high speed (30
KRPM) winders I've been involved with use red LEDs as built-in strobes,
but not very bright.

LED arrays with sub-millisecond flash duration for high speed machine
vision illumination are common. The LEDs are driven hard to get
brightness, so duty cycle is relatively low.

Like this:
http://www.advancedillumination.com/category/AL.html



You could get white light from three (RGB) LEDs and have the high speed.
It could even have many LEDs to get the desired brightness.

Tom

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Apparently, all but the one designated as the sparker are used only as
probes. No idea what is being probed for, or why.

Pin# - Use
1-3 - probe when required
4 - Anode (ie, positive)
5 - open
6 - probe when required
7 - Probe (no "when required")
8 - Sparker (will most likely be positive wrt the cathode)
9 - Cathode (ie, negative)

And based on the manuals (discussed below) pins 1, 4, and 9 are
actually used. (1 being one of the "probes", 4 being the anode, and 9
being the cathode). All other "probes" are only getting signal
capacitively coupled by the adjacent runs in the ribbon cable (perhaps
1-1/2" long).

O.K. My examination of the device shows that only one is
actually driven directly -- but the others appear to be capacitively
coupled through the ribbon cable. I haven't pulled the lamp socket out,
but based on the layout of the ribbon cable, I would expect the
"sparker" to be the middle of the set.

The circuit drawings seem to say that all are driven by a 5 KV pulse
through 22 picofarad capacitors, one per line.

If so, the "capacitors" are in reality parasitic capacitance
in that ribbon cable, as only the one is actually connected to anything,
at least on my 1531-A. The photo (Figure 4-10, page 26) in the manual
for the 1538-A shows the same construction, FWIW.

For the ribbon cable to parasitically couple to all pins, each with ~22
pF capacitance, the driven wire would have to be connected to every
other wire in the cable. Is this how it's wired?


One clue is that the max anode voltage is 1,000 volts. The sparker
voltage will be in that range, as the sparker is simply another nearby
electrode, albeit one not designed to handle the full flash energy.
Typically, an internal trigger takes less than the full holdoff voltage.

I recall that the flash capacitors are charged to 600 volts; don't know
where I got that tidbit.

Hmm ... the three main flash capacitors in the StroboTac are all
rated at 1000 VDC -- and selected by the range switch.

It may be 800 volts. It seems to depend on the model. It's easy to
achieve 600 volts with a voltage quadrupler, without a HV transformer.

Looking at the full schematic for the 1531-A, The anode and
cathode are respectively connected to +400V and -400V (developed from a
310V winding on the power transformer in the 1531-A), and in the 1538-A,
there appears to be a one-shot triggering the primary of a small
transformer as a DC-DC converter, which gives +800V.

Yes.


I don't find complete schematics for the 1538-A, though the
1531-A has the complete set. Both have the ghost views of the PC
traces. And, apparently, IET still services (and supplies parts) for
both models.

I wonder how much of GR's line IET took over? Or was it just a
case of renaming the company for whatever reason?

IET bought the manufacturing rights:

"Since 1976, IET Labs, Inc. has had a long-standing commitment to
conform the instruments and standards we offer to the customer's needs
rather than to have the customer settle for what is available. Our
ultimate goal is customer satisfaction.

In the year 2000, IET Labs acquired the GenRad standards, decade box,
audio and strobe product lines and now continues to service and support
these "In the Genrad Tradition..." Our experienced engineering and
service staff make it possible to offer: list"

From http://www.ietlabs.com/Company/index.html.


General radio was based in Concord, MA, while IET is based in Westbury,
NY.


It is pretty densely packed. The trigger transformer seems to
be in a potted brick -- and I *think* that the capacitor is included in
that brick.

It is, according to the circuit diagrams.

Making it rather difficult to check out.

Does anyone have a circuit diagram?

[ ... ]

I do see some current-production P-E flashlamps rated for 1,000 Hz, so
some kind of retrofit seems possible, although one may also need to
either replace or augment the trigger transformer.

O.K. Good luck with those.

I may also have a way to make an ordinary flashtube work far above its
normal flash rate, based on tricks used to get far above 25,000 plashes
per minute.

I've been reading the old patents listed in the back of "Electronic
flash, strobe", and two key ideas have emerged.

A little inductance in the discharge circuit (flash capacitor and
flashlamp) causes the discharge current to oscillate slightly, and the
resulting reverse voltage helps deionize the flashtube. I've seen a 20
microhenry inductor with a 500 microfarad flash capacitor in one circuit
diagram, giving a resonant period of 100 microsconds. Given that the
discharge current is easily 1,000 amps, the inductor will need to be air
core.

An inductance in the charging circuit (HV power supply and flash
capacitor) delays the charging current just after each flash just enough
to allow the the tube to deionize. I have not seen a component value on
this, but my rough computations indicate that something of order 300
millihenries could work.


I see that the FX-7A is suggested as the current replacement
lamp. I wonder what the prices are for that one?

I bet it's the same.

Joe Gwinn

So just use a few green LEDs and more reb and blue ones.

Again, so what if the color is off a bit.

Tom

"Martin H. Eastburn" wrote in message
...
The diodes come in so many mcandles of light. if all were the same then
the Green would blast the eye, then red and blue depending on the age of
victim.

Look at the sensitivity curve of light for the eye - it is complex.

Martin

Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Tm wrote:
Why would it need to be perfect? I would think close to white would be
fine. You could just use the correct number of red, green, and blue LEDs
and current drive them. You could even dump a cap into them with a SCR or
power mos device to get high peak power. A processor could do the display
and timing.

T


"Martin H. Eastburn" wrote in message
...

You would need a uP scanner with a program for delay and dwell between
and on each diode.
That or buy perfect spectral set of eye sensitivity level.

So not so easy but doable.

Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member


Tm wrote:

"Ned Simmons" wrote in message
...


In article ,
says...


Tm wrote:



Anyone try uaing one of the new super bright white LEDs for a strobe?


Somehow I doubt you could get a short enough flash to be
practical and I wonder about the max rep rate.
Intrested in the results if any one ever tries it.
...lew...

I don't know about white LEDs, but some of the small high speed (30
KRPM) winders I've been involved with use red LEDs as built-in strobes,
but not very bright.

LED arrays with sub-millisecond flash duration for high speed machine
vision illumination are common. The LEDs are driven hard to get
brightness, so duty cycle is relatively low.

Like this:
http://www.advancedillumination.com/category/AL.html



You could get white light from three (RGB) LEDs and have the high speed.
It could even have many LEDs to get the desired brightness.

Tom

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----




----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+
Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption
=----

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

And based on the manuals (discussed below) pins 1, 4, and 9 are
actually used. (1 being one of the "probes", 4 being the anode, and 9
being the cathode). All other "probes" are only getting signal
capacitively coupled by the adjacent runs in the ribbon cable (perhaps
1-1/2" long).

O.K. My examination of the device shows that only one is
actually driven directly -- but the others appear to be capacitively
coupled through the ribbon cable. I haven't pulled the lamp socket out,
but based on the layout of the ribbon cable, I would expect the
"sparker" to be the middle of the set.

The circuit drawings seem to say that all are driven by a 5 KV pulse
through 22 picofarad capacitors, one per line.

If so, the "capacitors" are in reality parasitic capacitance
in that ribbon cable, as only the one is actually connected to anything,
at least on my 1531-A. The photo (Figure 4-10, page 26) in the manual
for the 1538-A shows the same construction, FWIW.

For the ribbon cable to parasitically couple to all pins, each with ~22
pF capacitance, the driven wire would have to be connected to every
other wire in the cable. Is this how it's wired?

Only the center wire of the ribbon cable is connected to the
trigger module. It is possible that all of those 22 pF caps are inside
the stem, which has no apparent method of disassembly. (And the manual
simply shows how to *replace* it, not to repair it.

I could dig up the little digital capacitance meter and see what
it looks like, but I am a bit tired of this at this point. I'm now
trying to get a 1558-AP octave band noise analyzer working -- and while
the nicad packs still take and hold a charge (to my amazement, as I've
had it sitting around for several years since I got it from a hamfest),
the meter movement displays nothing. It would appear that one of the
movement's spiral springs to take current from the mount to the coil has
been damaged. Since I had to do some straightening of the folding
handle and one of the sideplates associated with it. Those are working
fine, but I have no idea what the sensitivity of the meter movement is.
Time to watch for another at hamfests, and see whether I can combine
them to make a working unit.

[ ... ]

I wonder how much of GR's line IET took over? Or was it just a
case of renaming the company for whatever reason?

IET bought the manufacturing rights:

"Since 1976, IET Labs, Inc. has had a long-standing commitment to
conform the instruments and standards we offer to the customer's needs
rather than to have the customer settle for what is available. Our
ultimate goal is customer satisfaction.

In the year 2000, IET Labs acquired the GenRad standards, decade box,
audio and strobe product lines and now continues to service and support
these "In the Genrad Tradition..." Our experienced engineering and
service staff make it possible to offer: list"

From http://www.ietlabs.com/Company/index.html.

So -- I should see what they charge for the meter? It appears
to be the same meter which is used in the 1551, which I think that they
still supply/service.

Nope -- I will still try contacting them, however.

I may also have a way to make an ordinary flashtube work far above its
normal flash rate, based on tricks used to get far above 25,000 plashes
per minute.

I've been reading the old patents listed in the back of "Electronic
flash, strobe", and two key ideas have emerged.

A little inductance in the discharge circuit (flash capacitor and
flashlamp) causes the discharge current to oscillate slightly, and the
resulting reverse voltage helps deionize the flashtube. I've seen a 20
microhenry inductor with a 500 microfarad flash capacitor in one circuit
diagram, giving a resonant period of 100 microsconds. Given that the
discharge current is easily 1,000 amps, the inductor will need to be air
core.

O.K. That could have been the purpose of the air-core inductor
in the supply which I duplicated. The wire was about #10 ga bare
copper, wound in a groove turned in a plexiglass cylinder the full
width of the case.

An inductance in the charging circuit (HV power supply and flash
capacitor) delays the charging current just after each flash just enough
to allow the the tube to deionize. I have not seen a component value on
this, but my rough computations indicate that something of order 300
millihenries could work.

O.K.

I see that the FX-7A is suggested as the current replacement
lamp. I wonder what the prices are for that one?

I bet it's the same.

Probably.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

And based on the manuals (discussed below) pins 1, 4, and 9 are
actually used. (1 being one of the "probes", 4 being the anode, and 9
being the cathode). All other "probes" are only getting signal
capacitively coupled by the adjacent runs in the ribbon cable (perhaps
1-1/2" long).

O.K. My examination of the device shows that only one is
actually driven directly -- but the others appear to be capacitively
coupled through the ribbon cable. I haven't pulled the lamp socket
out,
but based on the layout of the ribbon cable, I would expect the
"sparker" to be the middle of the set.

The circuit drawings seem to say that all are driven by a 5 KV pulse
through 22 picofarad capacitors, one per line.

If so, the "capacitors" are in reality parasitic capacitance
in that ribbon cable, as only the one is actually connected to anything,
at least on my 1531-A. The photo (Figure 4-10, page 26) in the manual
for the 1538-A shows the same construction, FWIW.

For the ribbon cable to parasitically couple to all pins, each with ~22
pF capacitance, the driven wire would have to be connected to every
other wire in the cable. Is this how it's wired?

Only the center wire of the ribbon cable is connected to the
trigger module. It is possible that all of those 22 pF caps are inside
the stem, which has no apparent method of disassembly. (And the manual
simply shows how to *replace* it, not to repair it.

I could dig up the little digital capacitance meter and see what
it looks like, but I am a bit tired of this at this point.

OK. Maybe someday.


I'm now
trying to get a 1558-AP octave band noise analyzer working -- and while
the nicad packs still take and hold a charge (to my amazement, as I've
had it sitting around for several years since I got it from a hamfest),
the meter movement displays nothing. It would appear that one of the
movement's spiral springs to take current from the mount to the coil has
been damaged. Since I had to do some straightening of the folding
handle and one of the sideplates associated with it. Those are working
fine, but I have no idea what the sensitivity of the meter movement is.
Time to watch for another at hamfests, and see whether I can combine
them to make a working unit.

[ ... ]

I wonder how much of GR's line IET took over? Or was it just a
case of renaming the company for whatever reason?

IET bought the manufacturing rights:

"Since 1976, IET Labs, Inc. has had a long-standing commitment to
conform the instruments and standards we offer to the customer's needs
rather than to have the customer settle for what is available. Our
ultimate goal is customer satisfaction.

In the year 2000, IET Labs acquired the GenRad standards, decade box,
audio and strobe product lines and now continues to service and support
these "In the Genrad Tradition..." Our experienced engineering and
service staff make it possible to offer: list"

From http://www.ietlabs.com/Company/index.html.

So -- I should see what they charge for the meter? It appears
to be the same meter which is used in the 1551, which I think that they
still supply/service.

Nope -- I will still try contacting them, however.

One can still buy meters, and there were only a few standard sizes, so a
retrofit is certainly possible. What will be lost is the
device-specific artwork (including scales) on the meter face.


I may also have a way to make an ordinary flashtube work far above its
normal flash rate, based on tricks used to get far above 25,000 plashes
per minute.

I've been reading the old patents listed in the back of "Electronic
flash, strobe", and two key ideas have emerged.

A little inductance in the discharge circuit (flash capacitor and
flashlamp) causes the discharge current to oscillate slightly, and the
resulting reverse voltage helps to deionize the flashtube. I've seen a 20
microhenry inductor with a 500 microfarad flash capacitor in one circuit
diagram, giving a resonant period of 100 microsconds. Given that the
discharge current is easily 1,000 amps, the inductor will need to be air
core.

O.K. That could have been the purpose of the air-core inductor
in the supply which I duplicated. The wire was about #10 ga bare
copper, wound in a groove turned in a plexiglass cylinder the full
width of the case.

How many turns? What is the diameter and length of the winding? There
are standard formulas to compute the inductance given this data.

What was this supply for?


An inductance in the charging circuit (HV power supply and flash
capacitor) delays the charging current just after each flash just enough
to allow the the tube to deionize. I have not seen a component value on
this, but my rough computations indicate that something of order 300
millihenries could work.

O.K.

If the 300-mH coil is properly oriented, the 1000-amp pulse from the
discharge-circuit coil will induce a bucking voltage in the charging
circuit, helping to deionize the tube. Or at least not defeat the 20-uH
coil. At least in theory - the pulse is very short.

Joe Gwinn

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

One can still buy meters, and there were only a few standard sizes, so a
retrofit is certainly possible. What will be lost is the
device-specific artwork (including scales) on the meter face.

The scale is a DB scale, and not the common range of a VU meter.
It is -6 to +10, plus white zones (on a black background) for "CAL" and
"BAT", so swapping in another meter will take some artwork.

The face shape of the meter is also uncommon, except in GR
equipment.

And nothing tells me what the full-scale current (or voltage)
is, other than the fact that there are three forward-biased diodes in
series across the meter, so it should not be any more than 2.1V FS.

Are these diodes only for protection, or do they also implement the log
function? There were meter movements with overly strong springs, so it
took a significant voltage to lift the pointer off the "zero" stop.
Such a meter could indicate the voltage across the diode string, which
is logarithmic in current.


I've done a bit of exploratory work with a stereo zoom
microscope, and the movement out of the case. It turns out that the top
hairspring is not firmly attached at the axis of the coil, though it is
attached at the outer end, and the bottom hairspring flexes as would be
expected throughout the range. I'm going to try my hand at re-soldering
the inner end of that -- after unsoldering the upper end and lifting away
the bridge with the jeweled bearing. It is certainly the kind of work
which is best done under the stereo-zoom microscope (it turns out that
mine is the AO version, not the B&L, FWIW.)

And a very steady hand...


At the moment, if I turn on the voltage check function, and then
tap the meter face, it makes contact long enough to send the meter to
beyond full scale occasionally, and to have it vibrating at a lower
level most of the rest of the time -- about 5/8th scale. The reason
that it goes beyond full scale is because only one hairspring is
resisting the force generated by the moving coil, so it moves beyond
where it normally would.

Sounds right.


O.K. That could have been the purpose of the air-core inductor
in the supply which I duplicated. The wire was about #10 ga bare
copper, wound in a groove turned in a plexiglass cylinder the full
width of the case.

How many turns? What is the diameter and length of the winding? There
are standard formulas to compute the inductance given this data.

This is from about 1966 or so, IIRC. You expect such details?

The coil form was long enough so it just barely fit inside a 19"
cabinet rack with about 15" of vertical panel space. Since there was
some space left at the ends to avoid breakdown to the mounting hardware,
that limits the coil to perhaps 15" to 17". Coil form diameter was
about 3", minus 1/2 the diameter of the wire to allow it to bottom in
the turned groove. Something like about 5 to 8 turns per inch, so that
would make it 75 to 136 turns.

I rest my case - you do remember, well enough to compute approximate
inductance.


What was this supply for?

Laser pump for Nd-Yag optically pumped laser. Max rep rate of
10 PPS. It was intended to be an illuminator for a night vision scope
which was gated on when the pulse was at the right distance, and off
afterwards to mimize the brightness of light sources within the field of
view. It was viewed by a three-stage image intensifier system before
the changeover to the micro-channel ones which could get the same gain
in a single tube.

I probably did calculate the inductance back when I made it.
The original design was to have it tapped for the ten 20uF 1KV
capacitors along its length to stretch the pulse, but that turned out to
not work well, so the pulse was going through the entire length of the
inductor from all of the capacitors in parallel.

This tapped inductor with capacitors is a lumped-component transmission
line, one kind of pulse-forming network. These were widely used in WW2
radars to generate the radar pulse, where one wants a constant power for
a fixed length of time (rather than the exponential decline of a simple
RC network).

I recall a passing note in Edgerton's book saying that lots of people
had tried to use pulse-forming networks to drive flashlamps, but the
wild variations in flashlamp impedance during the flash undermined all
their efforts.


It was charged from two big gray transformers made by UTC to be
able to get the caps back to full voltage within 100 mS.

In the lab, it was good for erasing print on paper. :-) The
power supply also lit me up rather spectacularly -- *once*. Between
left finger and right elbow (which was leaning on the case of the scope
on a cart.

Ten 20-uF caps at 1000 Volts is 100 Joules. Ouch! Good it was not from
arm to arm. A defibrillator is 400 Joules.


Joe Gwinn

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

The face shape of the meter is also uncommon, except in GR
equipment.

And nothing tells me what the full-scale current (or voltage)
is, other than the fact that there are three forward-biased diodes in
series across the meter, so it should not be any more than 2.1V FS.

Are these diodes only for protection, or do they also implement the log
function? There were meter movements with overly strong springs, so it
took a significant voltage to lift the pointer off the "zero" stop.
Such a meter could indicate the voltage across the diode string, which
is logarithmic in current.

That could indeed be what they are for. The zero adjust pin was
broken off the zero adjust screw, so I guess that was intentional,
rather than someone being ham-fisted in putting the meter face back on.

I've done a bit of exploratory work with a stereo zoom
microscope, and the movement out of the case. It turns out that the top
hairspring is not firmly attached at the axis of the coil, though it is
attached at the outer end, and the bottom hairspring flexes as would be
expected throughout the range. I'm going to try my hand at re-soldering
the inner end of that -- after unsoldering the upper end and lifting away
the bridge with the jeweled bearing. It is certainly the kind of work
which is best done under the stereo-zoom microscope (it turns out that
mine is the AO version, not the B&L, FWIW.)

And a very steady hand...

Of course. I've worked on camera shutters and iris diaphragms,
as well as other meters, so I figure on a reasonable chance at least.

At least the whole moving mechanism can be removed as a unit
from the magnet assembly, giving me a better chance at getting things
right without a magnet grabbing a tool just at the wrong moment. :-)

[ ... ]

How many turns? What is the diameter and length of the winding? There
are standard formulas to compute the inductance given this data.

This is from about 1966 or so, IIRC. You expect such details?

The coil form was long enough so it just barely fit inside a 19"
cabinet rack with about 15" of vertical panel space. Since there was
some space left at the ends to avoid breakdown to the mounting hardware,
that limits the coil to perhaps 15" to 17". Coil form diameter was
about 3", minus 1/2 the diameter of the wire to allow it to bottom in
the turned groove. Something like about 5 to 8 turns per inch, so that
would make it 75 to 136 turns.

I rest my case - you do remember, well enough to compute approximate
inductance.


What was this supply for?

Laser pump for Nd-Yag optically pumped laser. Max rep rate of
10 PPS. It was intended to be an illuminator for a night vision scope
which was gated on when the pulse was at the right distance, and off
afterwards to mimize the brightness of light sources within the field of
view. It was viewed by a three-stage image intensifier system before
the changeover to the micro-channel ones which could get the same gain
in a single tube.

I probably did calculate the inductance back when I made it.
The original design was to have it tapped for the ten 20uF 1KV
capacitors along its length to stretch the pulse, but that turned out to
not work well, so the pulse was going through the entire length of the
inductor from all of the capacitors in parallel.

This tapped inductor with capacitors is a lumped-component transmission
line, one kind of pulse-forming network. These were widely used in WW2
radars to generate the radar pulse, where one wants a constant power for
a fixed length of time (rather than the exponential decline of a simple
RC network).

Yep! That was the intention when our "customers" asked for that
feature.

I recall a passing note in Edgerton's book saying that lots of people
had tried to use pulse-forming networks to drive flashlamps, but the
wild variations in flashlamp impedance during the flash undermined all
their efforts.

Probably why this did nothing useful. :-)


It was charged from two big gray transformers made by UTC to be
able to get the caps back to full voltage within 100 mS.

In the lab, it was good for erasing print on paper. :-) The
power supply also lit me up rather spectacularly -- *once*. Between
left finger and right elbow (which was leaning on the case of the scope
on a cart.

Ten 20-uF caps at 1000 Volts is 100 Joules. Ouch! Good it was not from
arm to arm. A defibrillator is 400 Joules.

But it *was* from arm to arm. Remember -- between left (index) finger
and right elbow.

It seemed to take five minutes before I realized that the noise
which was getting in the way of my checking for my heartbeat *was* my
heartbeat.

Shortly after that, I pushed for our lab to send everyone who
wanted it to a CPR class. These days, we would have to stock anti-AIDS
mouthpieces for use just in case. :-)

I also once (intentionally) dumped that cap bank into a 10 ohm 2
Watt carbon resistor. Parts of that wound up embedded in the ceiling
acoustic tile. :-) Yes -- I did make sure that nobody was in the path of
the expected shrapnel. :-)


Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

The face shape of the meter is also uncommon, except in GR
equipment.

And nothing tells me what the full-scale current (or voltage)
is, other than the fact that there are three forward-biased diodes in
series across the meter, so it should not be any more than 2.1V FS.

Are these diodes only for protection, or do they also implement the log
function? There were meter movements with overly strong springs, so it
took a significant voltage to lift the pointer off the "zero" stop.
Such a meter could indicate the voltage across the diode string, which
is logarithmic in current.

That could indeed be what they are for. The zero adjust pin was
broken off the zero adjust screw, so I guess that was intentional,
rather than someone being ham-fisted in putting the meter face back on.

If you can see the pole faces, does the magnetic gap vary with movement
angle? This is the other way to implement a log meter.


I've done a bit of exploratory work with a stereo zoom
microscope, and the movement out of the case. It turns out that the top
hairspring is not firmly attached at the axis of the coil, though it is
attached at the outer end, and the bottom hairspring flexes as would be
expected throughout the range. I'm going to try my hand at re-soldering
the inner end of that -- after unsoldering the upper end and lifting away
the bridge with the jeweled bearing. It is certainly the kind of work
which is best done under the stereo-zoom microscope (it turns out that
mine is the AO version, not the B&L, FWIW.)

And a very steady hand...

Of course. I've worked on camera shutters and iris diaphragms,
as well as other meters, so I figure on a reasonable chance at least.

At least the whole moving mechanism can be removed as a unit
from the magnet assembly, giving me a better chance at getting things
right without a magnet grabbing a tool just at the wrong moment. :-)

[ ... ]

How many turns? What is the diameter and length of the winding? There
are standard formulas to compute the inductance given this data.

This is from about 1966 or so, IIRC. You expect such details?

The coil form was long enough so it just barely fit inside a 19"
cabinet rack with about 15" of vertical panel space. Since there was
some space left at the ends to avoid breakdown to the mounting hardware,
that limits the coil to perhaps 15" to 17". Coil form diameter was
about 3", minus 1/2 the diameter of the wire to allow it to bottom in
the turned groove. Something like about 5 to 8 turns per inch, so that
would make it 75 to 136 turns.

I rest my case - you do remember, well enough to compute approximate
inductance.

I compute a 100 to 260 microhenries.


What was this supply for?

Laser pump for Nd-Yag optically pumped laser. Max rep rate of
10 PPS. It was intended to be an illuminator for a night vision scope
which was gated on when the pulse was at the right distance, and off
afterwards to mimize the brightness of light sources within the field of
view. It was viewed by a three-stage image intensifier system before
the changeover to the micro-channel ones which could get the same gain
in a single tube.

I probably did calculate the inductance back when I made it.
The original design was to have it tapped for the ten 20uF 1KV
capacitors along its length to stretch the pulse, but that turned out to
not work well, so the pulse was going through the entire length of the
inductor from all of the capacitors in parallel.

This tapped inductor with capacitors is a lumped-component transmission
line, one kind of pulse-forming network. These were widely used in WW2
radars to generate the radar pulse, where one wants a constant power for
a fixed length of time (rather than the exponential decline of a simple
RC network).

Yep! That was the intention when our "customers" asked for that
feature.

I recall a passing note in Edgerton's book saying that lots of people
had tried to use pulse-forming networks to drive flashlamps, but the
wild variations in flashlamp impedance during the flash undermined all
their efforts.

Probably why this did nothing useful. :-)

Yep. It worked pretty well with hard-vacuum tubes, like magnetrons.


It was charged from two big gray transformers made by UTC to be
able to get the caps back to full voltage within 100 mS.

In the lab, it was good for erasing print on paper. :-) The
power supply also lit me up rather spectacularly -- *once*. Between
left finger and right elbow (which was leaning on the case of the scope
on a cart.

Ten 20-uF caps at 1000 Volts is 100 Joules. Ouch! Good it was not from
arm to arm. A defibrillator is 400 Joules.

But it *was* from arm to arm. Remember -- between left (index) finger
and right elbow.

It seemed to take five minutes before I realized that the noise
which was getting in the way of my checking for my heartbeat *was* my
heartbeat.

Shortly after that, I pushed for our lab to send everyone who
wanted it to a CPR class. These days, we would have to stock anti-AIDS
mouthpieces for use just in case. :-)

Right. You were very lucky in the timing (with respect to your
heartbeat) of the shock.


I also once (intentionally) dumped that cap bank into a 10 ohm 2
Watt carbon resistor. Parts of that wound up embedded in the ceiling
acoustic tile. :-) Yes -- I did make sure that nobody was in the path of
the expected shrapnel. :-)

Did you explode any wire?


Joe Gwinn

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Such a meter could indicate the voltage across the diode string, which
is logarithmic in current.

That could indeed be what they are for. The zero adjust pin was
broken off the zero adjust screw, so I guess that was intentional,
rather than someone being ham-fisted in putting the meter face back on.

If you can see the pole faces, does the magnetic gap vary with movement
angle? This is the other way to implement a log meter.

Nope! constant gap, as in most other meters that I have seen.

I just spent this evening in the shop, making a fixture to mount
the meter movement onto while I'm working on it, since there is not
otherwise any reasonable way to grip it.

The fixture also has one of a bunch of plastic TV-dinner pans
(for something like macaroni and cheese) firmly attached between the
brass hex standoffs (brass to avoid interaction with the magnet). That
serves two functions, here.

1) To catch small parts if I drop them.

2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

The work will be done under a stereo-zoom microscope (3-70X)
with its own illumination, and I'll be using non-magnetic tweezers for
manipulating the hair-spring.

The soldering iron (An old "Loner") is mostly a non-magnetic
alloy of stainless steel, so it should not fall victim to the magnet.
(But I will have to remove the entire movement from the magnet assembly
to gain access to the point which I need to re-solder.

If this fails (for whatever reason), I've got a brother to the
system bookmarked on eBay. That one is missing quite a few parts,
including some special dials, which should keep the serious bids down.
It *does* have the meter, at least.

[ ... ]

How many turns? What is the diameter and length of the winding? There
are standard formulas to compute the inductance given this data.

This is from about 1966 or so, IIRC. You expect such details?

The coil form was long enough so it just barely fit inside a 19"
cabinet rack with about 15" of vertical panel space. Since there was
some space left at the ends to avoid breakdown to the mounting hardware,
that limits the coil to perhaps 15" to 17". Coil form diameter was
about 3", minus 1/2 the diameter of the wire to allow it to bottom in
the turned groove. Something like about 5 to 8 turns per inch, so that
would make it 75 to 136 turns.

I rest my case - you do remember, well enough to compute approximate
inductance.

I compute a 100 to 260 microhenries.

That sounds reasonable.

[ ... ]

Yep! That was the intention when our "customers" asked for that
feature.

I recall a passing note in Edgerton's book saying that lots of people
had tried to use pulse-forming networks to drive flashlamps, but the
wild variations in flashlamp impedance during the flash undermined all
their efforts.

Probably why this did nothing useful. :-)

Yep. It worked pretty well with hard-vacuum tubes, like magnetrons.

O.K. That may be where they got the idea.

[ ... ]

Ten 20-uF caps at 1000 Volts is 100 Joules. Ouch! Good it was not from
arm to arm. A defibrillator is 400 Joules.

But it *was* from arm to arm. Remember -- between left (index) finger
and right elbow.

It seemed to take five minutes before I realized that the noise
which was getting in the way of my checking for my heartbeat *was* my
heartbeat.

Shortly after that, I pushed for our lab to send everyone who
wanted it to a CPR class. These days, we would have to stock anti-AIDS
mouthpieces for use just in case. :-)

Right. You were very lucky in the timing (with respect to your
heartbeat) of the shock.

Agreed. FWIW -- I was quite young then, and I think that the
odds of my surviving such another time would be rather slim.

I also once (intentionally) dumped that cap bank into a 10 ohm 2
Watt carbon resistor. Parts of that wound up embedded in the ceiling
acoustic tile. :-) Yes -- I did make sure that nobody was in the path of
the expected shrapnel. :-)

Did you explode any wire?

Nope -- but I did (on a bet) cut a power cord with a pair of
diagonal pliers without insulating gloves. I just made sure to specify
that it would be *his* diagonal pliers, not mine. :-) The floor was
linoleum tile over concrete, and my shoes were rubber soled, so I was
well enough insulated, and as expected, the primary path of the
electrons was between hot and neutral through the expansing gasses of
what had once been the blades of the dikes. :-) Of course, the circuit
breaker tripped rather quickly.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Such a meter could indicate the voltage across the diode string, which
is logarithmic in current.

That could indeed be what they are for. The zero adjust pin was
broken off the zero adjust screw, so I guess that was intentional,
rather than someone being ham-fisted in putting the meter face back on.

If you can see the pole faces, does the magnetic gap vary with movement
angle? This is the other way to implement a log meter.

Nope! constant gap, as in most other meters that I have seen.

That pretty well clinches it.

Diodes are far cheaper than special meter movements.


I just spent this evening in the shop, making a fixture to mount
the meter movement onto while I'm working on it, since there is not
otherwise any reasonable way to grip it.

The fixture also has one of a bunch of plastic TV-dinner pans
(for something like macaroni and cheese) firmly attached between the
brass hex standoffs (brass to avoid interaction with the magnet). That
serves two functions, here.

1) To catch small parts if I drop them.

Unless they bounce right out. A pan liner of some kind may be necessary.


2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

Good point. It's real hard to clean a magnet assembly that has
collected iron filings.

I'd also sweep the bench with a strong magnet in a bag first, to reduce
the supply of iron filings in the first place.


The work will be done under a stereo-zoom microscope (3-70X)
with its own illumination, and I'll be using non-magnetic tweezers for
manipulating the hair-spring.

The soldering iron (An old "Loner") is mostly a non-magnetic
alloy of stainless steel, so it should not fall victim to the magnet.
(But I will have to remove the entire movement from the magnet assembly
to gain access to the point which I need to re-solder.

A new retirement business - fixing meter movements. Then, move up to
crashed disk drives.


If this fails (for whatever reason), I've got a brother to the
system bookmarked on eBay. That one is missing quite a few parts,
including some special dials, which should keep the serious bids down.
It *does* have the meter, at least.

[ ... ]

Yep! That was the intention when our "customers" asked for that
feature [the pulse-forming network].

I recall a passing note in Edgerton's book saying that lots of people
had tried to use pulse-forming networks to drive flashlamps, but the
wild variations in flashlamp impedance during the flash undermined all
their efforts.

Probably why this did nothing useful. :-)

Yep. It worked pretty well with hard-vacuum tubes, like magnetrons.

O.K. That may be where they got the idea.

Exactly. It was mostly the same people working on both, at least the
MIT crowd. Edgerton was a MIT professor.


Ten 20-uF caps at 1000 Volts is 100 Joules. Ouch! Good it was not
from arm to arm. A defibrillator is 400 Joules.

But it *was* from arm to arm. Remember -- between left (index) finger
and right elbow.

It seemed to take five minutes before I realized that the noise
which was getting in the way of my checking for my heartbeat *was* my
heartbeat.

Shortly after that, I pushed for our lab to send everyone who
wanted it to a CPR class. These days, we would have to stock anti-AIDS
mouthpieces for use just in case. :-)

Right. You were very lucky in the timing (with respect to your
heartbeat) of the shock.

Agreed. FWIW -- I was quite young then, and I think that the
odds of my surviving such another time would be rather slim.

Actually, age has little to do with it. Timing is everything.


I also once (intentionally) dumped that cap bank into a 10 ohm 2
Watt carbon resistor. Parts of that wound up embedded in the ceiling
acoustic tile. :-) Yes -- I did make sure that nobody was in the path of
the expected shrapnel. :-)

Did you explode any wire?

Nope -- but I did (on a bet) cut a power cord with a pair of
diagonal pliers without insulating gloves. I just made sure to specify
that it would be *his* diagonal pliers, not mine. :-) The floor was
linoleum tile over concrete, and my shoes were rubber soled, so I was
well enough insulated, and as expected, the primary path of the
electrons was between hot and neutral through the expansing gasses of
what had once been the blades of the dikes. :-) Of course, the circuit
breaker tripped rather quickly.

The classic dodge is to nip the power cord halfway, cutting one wire at
a time. Easy with flat cable, harder with round cable, but not
impossible. But I assume that the point of the bet was to make a big
bang and yet survive to collect.


Joe Gwinn

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

If you can see the pole faces, does the magnetic gap vary with movement
angle? This is the other way to implement a log meter.

Nope! constant gap, as in most other meters that I have seen.

That pretty well clinches it.

Diodes are far cheaper than special meter movements.

Well ... I was wrong. One pole piece was like a marriage
between the top of a parentheses and the bottom of a '|', but it was
hidden inside the frame of the movement assembly, so I could not see it
until I separated the movement from the magnet and pole pieces.

[ ... ]

1) To catch small parts if I drop them.

Unless they bounce right out. A pan liner of some kind may be necessary.

Or -- unless I'm carrying the coil and needle assembly to
elsewhere, to get other tools for adjusting the spring which I had just
soldered on, and the spring separated from my solder joint somewhere
over a *very* cluttered shop floor.

So -- on to the spare-parts machine on eBay. :-(

The alternative is to find another meter to act as a spring
donor.


2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

Good point. It's real hard to clean a magnet assembly that has
collected iron filings.

I'd also sweep the bench with a strong magnet in a bag first, to reduce
the supply of iron filings in the first place.

Good plan, though I had not done any filings generating work on
that bench. There is a shear on it, and a corner notching shear, and a
reloading press, none of which tend to generate filings.

The work will be done under a stereo-zoom microscope (3-70X)
with its own illumination, and I'll be using non-magnetic tweezers for
manipulating the hair-spring.

The soldering iron (An old "Loner") is mostly a non-magnetic
alloy of stainless steel, so it should not fall victim to the magnet.
(But I will have to remove the entire movement from the magnet assembly
to gain access to the point which I need to re-solder.

A new retirement business - fixing meter movements. Then, move up to
crashed disk drives.

I've obviously got to get better at it, first. :-)


If this fails (for whatever reason), I've got a brother to the
system bookmarked on eBay. That one is missing quite a few parts,
including some special dials, which should keep the serious bids down.
It *does* have the meter, at least.

And that is what I'll have to do, now.

[ ... ]

Yep. It worked pretty well with hard-vacuum tubes, like magnetrons.

O.K. That may be where they got the idea.

Exactly. It was mostly the same people working on both, at least the
MIT crowd. Edgerton was a MIT professor.

But this was an army lab, working only with optical stuff,
including the lasers as long-distance illuminators. No RADAR stuff
there.

[ ... ]

Did you explode any wire?

Nope -- but I did (on a bet) cut a power cord with a pair of
diagonal pliers without insulating gloves. I just made sure to specify
that it would be *his* diagonal pliers, not mine. :-) The floor was
linoleum tile over concrete, and my shoes were rubber soled, so I was
well enough insulated, and as expected, the primary path of the
electrons was between hot and neutral through the expansing gasses of
what had once been the blades of the dikes. :-) Of course, the circuit
breaker tripped rather quickly.

The classic dodge is to nip the power cord halfway, cutting one wire at
a time. Easy with flat cable, harder with round cable, but not
impossible. But I assume that the point of the bet was to make a big
bang and yet survive to collect.

Of course. :-) It was a length of zip cord -- the cord for one
of the early Ungar soldering irons, IIRC -- the ones with the screw-in
heating elements, instead of the later ones which plug-in elements.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

In article , DoN. Nichols says...

2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

Common indeed. The key to repairing a moving coil meter like that
that's jammed from magnetic swarf in between the pole pieces, is to
simply unbolt the magnet from the movement.

You MUST store it with a keeper.

Once it's off the movement, blow or brush the debris out of the
way.

I've unstuck a bunch of simpson meters with hang-y meters this way.

The diodes BTW are protection diodes. They prevent the coil from
blowing out by shunting any voltage more than 0.7 volts around
the meter.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

According to jim rozen :
In article , DoN. Nichols says...

2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

Common indeed. The key to repairing a moving coil meter like that
that's jammed from magnetic swarf in between the pole pieces, is to
simply unbolt the magnet from the movement.

[ ... ]

Once it's off the movement, blow or brush the debris out of the
way.

Indeed so.

I've unstuck a bunch of simpson meters with hang-y meters this way.

The diodes BTW are protection diodes. They prevent the coil from
blowing out by shunting any voltage more than 0.7 volts around
the meter.

Well ... in this case, 2.1 volts, as there are three silicon
diodes in series. (Even without looking them up, I know that they are
not germanium diodes, because only the silicon ones have their glass
cases painted black -- presumably to eliminate photoelectron
generation.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 28 Apr 2006 19:08:36 -0700, jim rozen
wrote:

snip
The diodes BTW are protection diodes. They prevent the coil from
blowing out by shunting any voltage more than 0.7 volts around
the meter.

Hi Jim,

I hated those diodes in meters. Next to worthless trying to
use one when working on a transmitter.

Read DC voltage, key mic to see if voltage drops, watch
meter read backwards...

Either had to clip the diode train out of the circuit or go
find a different meter without them.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]


1) To catch small parts if I drop them.

Unless they bounce right out. A pan liner of some kind may be necessary.

Or -- unless I'm carrying the coil and needle assembly to
elsewhere, to get other tools for adjusting the spring which I had just
soldered on, and the spring separated from my solder joint somewhere
over a *very* cluttered shop floor.

So -- on to the spare-parts machine on eBay. :-(

The alternative is to find another meter to act as a spring
donor.

Damn!


2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

Good point. It's real hard to clean a magnet assembly that has
collected iron filings.

I'd also sweep the bench with a strong magnet in a bag first, to reduce
the supply of iron filings in the first place.

Good plan, though I had not done any filings generating work on
that bench. There is a shear on it, and a corner notching shear, and a
reloading press, none of which tend to generate filings.

But they do generate slivers.


The work will be done under a stereo-zoom microscope (3-70X)
with its own illumination, and I'll be using non-magnetic tweezers for
manipulating the hair-spring.

The soldering iron (An old "Loner") is mostly a non-magnetic
alloy of stainless steel, so it should not fall victim to the magnet.
(But I will have to remove the entire movement from the magnet assembly
to gain access to the point which I need to re-solder.

A new retirement business - fixing meter movements. Then, move up to
crashed disk drives.

I've obviously got to get better at it, first. :-)

Well, use a carrying pan. I go to yard sales and the like, and get old
stainless steel cookware for use in the shop: they make good parts
trays, and are solvent-proof.



Yep. It worked pretty well with hard-vacuum tubes, like magnetrons.

O.K. That may be where they got the idea.

Exactly. It was mostly the same people working on both, at least the
MIT crowd. Edgerton was a MIT professor.

But this was an army lab, working only with optical stuff,
including the lasers as long-distance illuminators. No RADAR stuff
there.

Where was this?


Did you explode any wire?

Nope -- but I did (on a bet) cut a power cord with a pair of
diagonal pliers without insulating gloves. I just made sure to specify
that it would be *his* diagonal pliers, not mine. :-) The floor was
linoleum tile over concrete, and my shoes were rubber soled, so I was
well enough insulated, and as expected, the primary path of the
electrons was between hot and neutral through the expansing gasses of
what had once been the blades of the dikes. :-) Of course, the circuit
breaker tripped rather quickly.

The classic dodge is to nip the power cord halfway, cutting one wire at
a time. Easy with flat cable, harder with round cable, but not
impossible. But I assume that the point of the bet was to make a big
bang and yet survive to collect.

Of course. :-) It was a length of zip cord -- the cord for one
of the early Ungar soldering irons, IIRC -- the ones with the screw-in
heating elements, instead of the later ones which plug-in elements.

I gather you won the bet.

Joe Gwinn

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Or -- unless I'm carrying the coil and needle assembly to
elsewhere, to get other tools for adjusting the spring which I had just
soldered on, and the spring separated from my solder joint somewhere
over a *very* cluttered shop floor.

So -- on to the spare-parts machine on eBay. :-(

The alternative is to find another meter to act as a spring
donor.

Damn!

Well ... I just won the spare parts one on eBay for $24.95. As
I expected, there were no other bidders, given the *obviously* missing
parts.

[ ... ]

Good plan, though I had not done any filings generating work on
that bench. There is a shear on it, and a corner notching shear, and a
reloading press, none of which tend to generate filings.

But they do generate slivers.

Yes -- but have mostly been used on aluminum, which at least
tends to generate non-magnetic slivers. :-)

[ ... ]

A new retirement business - fixing meter movements. Then, move up to
crashed disk drives.

I've obviously got to get better at it, first. :-)

Well, use a carrying pan. I go to yard sales and the like, and get old
stainless steel cookware for use in the shop: they make good parts
trays, and are solvent-proof.

Yes -- I had thought that the hairspring was firmly soldered to
the coil, so I wasn't worried. *wrong*!. :-(

[ ... ]

Exactly. It was mostly the same people working on both, at least the
MIT crowd. Edgerton was a MIT professor.

But this was an army lab, working only with optical stuff,
including the lasers as long-distance illuminators. No RADAR stuff
there.

Where was this?

U.S. Army Night Vision Labs (at that time -- it has since gone
through quite a few name changes -- once three in a single year. :-)
Location was (and still is Ft. Belvoir, VA.)

[ ... ]

Nope -- but I did (on a bet) cut a power cord with a pair of
diagonal pliers without insulating gloves. I just made sure to specify

[ ... ]

The classic dodge is to nip the power cord halfway, cutting one wire at
a time. Easy with flat cable, harder with round cable, but not
impossible. But I assume that the point of the bet was to make a big
bang and yet survive to collect.

Of course. :-) It was a length of zip cord -- the cord for one
of the early Ungar soldering irons, IIRC -- the ones with the screw-in
heating elements, instead of the later ones which plug-in elements.

I gather you won the bet.

Yes.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

In article ,
(DoN. Nichols) wrote:

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Or -- unless I'm carrying the coil and needle assembly to
elsewhere, to get other tools for adjusting the spring which I had just
soldered on, and the spring separated from my solder joint somewhere
over a *very* cluttered shop floor.

So -- on to the spare-parts machine on eBay. :-(

The alternative is to find another meter to act as a spring
donor.

Damn!

Well ... I just won the spare parts one on eBay for $24.95. As
I expected, there were no other bidders, given the *obviously* missing
parts.

Hope the meter is OK.


Good plan, though I had not done any filings generating work on
that bench. There is a shear on it, and a corner notching shear, and a
reloading press, none of which tend to generate filings.

But they do generate slivers.

Yes -- but have mostly been used on aluminum, which at least
tends to generate non-magnetic slivers. :-)

Yes, but still, a good vacuum cleaning and washdown is in order.


Exactly. It was mostly the same people working on both, at least the
MIT crowd. Edgerton was a MIT professor.

But this was an army lab, working only with optical stuff,
including the lasers as long-distance illuminators. No RADAR stuff
there.

Where was this?

U.S. Army Night Vision Labs (at that time -- it has since gone
through quite a few name changes -- once three in a single year. :-)
Location was (and still is Ft. Belvoir, VA.)

OK. But I bet they read the MIT Radiation Labs series (which laid out
the technical basis for radar, as developed in great secrecy during WW2).


Joe Gwinn

According to Joseph Gwinn :
In article ,
(DoN. Nichols) wrote:

[ ... ]

Well ... I just won the spare parts one on eBay for $24.95. As
I expected, there were no other bidders, given the *obviously* missing
parts.

Hope the meter is OK.

So do I. But if all else fails, it is at least a possible donor
for two more hairsprings. :-)

From the photo, it looks as though the faceplate is slightly
melted on the top right side -- but I can swap the faceplate from my
other one into that. It *may* be simply another JPEG artifact, as the
photo was rather heavily JPEGed. Or it could be dirt, or reflections.
It is right next to the missing special knob, in any case. The special
knob has a transparent flange with a white dot of its own, and two DB
scales. The outer scale ranges from 50 to 140DB, and the inner one from
0 to -50. You start the measurements with both switches fully CW, and
you adjust one knob if the meter reads below 0 dB, or the other if it
reads above +10 dB. For calibration, you set both white dots pointing
straight up.

If you care to look at it, the eBay auction number is
7612826976.

Aside from the rather special switch knob missing, there is also
the clamshell case bottom/top and the linkage which joins them and
allows opening/closing without ever letting the parts separate.

Good plan, though I had not done any filings generating work on
that bench. There is a shear on it, and a corner notching shear, and a
reloading press, none of which tend to generate filings.

But they do generate slivers.

Yes -- but have mostly been used on aluminum, which at least
tends to generate non-magnetic slivers. :-)

Yes, but still, a good vacuum cleaning and washdown is in order.

Agreed -- except a washdown is pretty difficult with so many
large tools bolted in place on that bench. At least all of them are
within my lifting ability -- unlike with the 24" DiAcro brake, for which
I would have to get the engine hoist. :-)

[ ... ]

Where was this?

U.S. Army Night Vision Labs (at that time -- it has since gone
through quite a few name changes -- once three in a single year. :-)
Location was (and still is Ft. Belvoir, VA.)

OK. But I bet they read the MIT Radiation Labs series (which laid out
the technical basis for radar, as developed in great secrecy during WW2).

Quite likely. Or encountered it in their college classes
recently enough so they still remembered it.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---