"Angrie.Woman" wrote in message
...
wrote:
In sci.electronics.repair NSM wrote:

Nonsense. It's not the lead that's dangerous, it's the tube which might
have
a charge although that's most unlikely. A quick whack with a clip lead
will
empty that. 1 minute after, maybe. 6 months, no way.


Depends mostly on the quality of the rectifier, and on whether there are
any bleeding resistors or voltage dividers. Give a vacuum type HV
rectifier and no bleeding resistors it should be easily possible that a
picture tube retains high voltage for weeks.


Sigh. And since my original post was that a child should not take apart
a TV unless a grown-up knows how to discharge the thing that holds the
charge...it is likely we're all in agreement essentially.

A

Well that's certainly true, though mostly due to the implosion hazard.

"Rita D Berkowitz" bravely wrote to "All" (24 Jun 05 16:04:45)
--- on the heady topic of " Any parts of a LASERJET 5Si that can be
salvaged?"

RDB From: "Rita D Berkowitz" ritaberk2O04 @aol.com
RDB Xref: aeinews rec.crafts.metalworking:25915
RDB alt.marketing.online.ebay:26941 sci.electronics.repair:51363
RDB "NSM" wrote in message...

Any TV that's been sitting for a week won't have a charge in it.

RDB BULL****! Put your tongue on the HV lead of the flyback transformer
RDB six months after you unplugged it and you'll probably **** all over
RDB yourself if you are lucky..


Rita?

The HV rectifier is typically a little leaky (especially when hotter)
and will by itself gently bleed off the charge (if 1^12 ohms and 25nF,
this is about 34 hours). But most HV sections have the focus divider
at the output of the rectifier and this will quickly drain the charge,
in under 2 minutes (about 500Meg ohms).

A*s*i*m*o*v

.... Wasted power is current squared times the resistance.

"James Sweet" wrote in message
news:773ve.1986$Uc2.1802@trnddc03...

I'd do it, I pretty regularly touch flyback HV leads, there's nothing in
the
flyback that can store a charge, the tube itself does that. A B&W monitor
or
a vacuum tube TV chassis can hold a charge for quite some time, but a
solid
state color set has a focus divider that'll discharge the HV within
minutes.
It's still always wise to ground the anode just in case though.

You sure don't want to touch the ungrounded coating on a picture tube a
minute after switchoff while standing in a second story window. True story.

N

In sci.electronics.repair Tom Quackenbush wrote:
Completely off topic, but would you happen to know if "Quackenbush"
(Quackenbos?, Kwakkenbos?) means anything in Dutch?

Maybe the name of a location. As a word it has no real meaning.

---
Met vriendelijke groet,

Maarten Bakker.

In sci.electronics.repair wrote:
In sci.electronics.repair Tom Quackenbush wrote:
Completely off topic, but would you happen to know if "Quackenbush"
(Quackenbos?, Kwakkenbos?) means anything in Dutch?
Maybe the name of a location. As a word it has no real meaning.

Ah, only now I see your name... I don't know about it's etimology. It
could have something to do with ducks and wood, maybe your ancestors
lived near a ducktrap. I guess that's not too good an explanation...

---
Met vriendelijke groet,

Maarten Bakker.

On Fri, 24 Jun 2005 16:04:45 -0400, "Rita Ä Berkowitz" ritaberk2O04
@aol.com wrote:

"NSM" wrote in message...

Any TV that's been sitting for a week won't have a charge in it.

BULL****! Put your tongue on the HV lead of the flyback transformer six
months after you unplugged it and you'll probably **** all over yourself if
you are lucky..



Rita


True...PC monitors seem to be a different story, in my experience.

Tom

On Fri, 24 Jun 2005 20:12:23 -0400, JohnM wrote:

Angrie.Woman wrote:
JohnM wrote:

Rita Ä Berkowitz wrote:

"NSM" wrote in message...


Any TV that's been sitting for a week won't have a charge in it.




BULL****! Put your tongue on the HV lead of the flyback transformer six
months after you unplugged it and you'll probably **** all over
yourself if
you are lucky..



Rita



I've never considered ****ing all over myself to be a lucky thing..


I think the alternative is having your heart stop from the shock.

A

How about if I just don't put my tongue on electrical stuff, then I
won't have to be thankful for ****ing myself;-)

I think I just don't ever want to be thankful for that..

John

Here I am with my story again...

We have, most of us, tongue-tested a 9 volt battery, I think. I once,
foolishly, tested a 10.6 VDC, 850 mA cellular telephone charger. Big
mistake... :-)

Tom

On Sat, 25 Jun 2005 01:25:45 GMT, "BrotherBart"
wrote:

If you've got no pride, just pick up anything but a TV (unless you know
how to discharge the cap) from the garbage and give it a go.

When I was five years old my dad was less than impressed when I took his
pocket watch apart.


BG

My dad was a very good backyard mechanic, but for some reason didn't
get into the more intricate stuff. One sunny summer Saturday morning,
I placed a sheet of plywood on the ground, removed the Carter BBD (I
think) carburator from the 225 slant-six motor in the 1965 Dodge
Polara station wagon he was preparing for the road, and stripped it
down on the sheet of plywood. My dad had worked a backshift, and at
about 1130 or so came outside, and turned white as a sheet. He said,
"Are you sure you can get that thing back together?" I assured him
that I could, and I did, and the car lived to ride again. :-)

I still don't understand why a man who could strip down a motor or
transmission, install new rings, valves, etc., had a problem with a
carburator...I couldn't rebuild a motor to save my own life, but I've
rebuilt a number of carburators...strange.

Tom

Tom MacIntyre wrote:



Here I am with my story again...

We have, most of us, tongue-tested a 9 volt battery, I think. I once,
foolishly, tested a 10.6 VDC, 850 mA cellular telephone charger. Big
mistake... :-)

I always have a story. In high school, I took a year of beginning
electronics.

During the first week, out teacher opened up a TV to show us how much power
was still present even though the the set was unplugged. He then proceeded
to show us how to discharge the thing that held the charge. Apparently,
using
a borrowed screwdriver that had a crack in the handle is not the proper way.

Angie

On Sat, 25 Jun 2005 16:30:09 GMT, "Angrie.Woman"
wrote:

Tom MacIntyre wrote:



Here I am with my story again...

We have, most of us, tongue-tested a 9 volt battery, I think. I once,
foolishly, tested a 10.6 VDC, 850 mA cellular telephone charger. Big
mistake... :-)

I always have a story. In high school, I took a year of beginning
electronics.

During the first week, out teacher opened up a TV to show us how much power
was still present even though the the set was unplugged. He then proceeded
to show us how to discharge the thing that held the charge. Apparently,
using
a borrowed screwdriver that had a crack in the handle is not the proper way.

Angie

BG

With solid state-uP based sets, the proper way involves the slow
draining of the voltage/current anyway...through a high-value
resistor.

One time we were sending a bunch of CRT's back to the manufacturer for
proof-of- replacement one time, and my wife was labelling them. She
was wearing a knitted sweater, and the sleeve brushed against the 2nd
anode. She wasn't pleased with the result. The CRT had been sitting
for weeks to months...

Tom

My dad was a very good backyard mechanic, but for some reason didn't
get into the more intricate stuff. One sunny summer Saturday morning,
I placed a sheet of plywood on the ground, removed the Carter BBD (I
think) carburator from the 225 slant-six motor in the 1965 Dodge
Polara station wagon he was preparing for the road, and stripped it
down on the sheet of plywood. My dad had worked a backshift, and at
about 1130 or so came outside, and turned white as a sheet. He said,
"Are you sure you can get that thing back together?" I assured him
that I could, and I did, and the car lived to ride again. :-)

A little word of advice to the technically curious youngsters out there.
NEVER use your mother the beautician's professional diamond coated nail file
to deburr the driveshaft of the lawn mower engine you are rebuilding.

It makes your butt hurt really bad.

"Tom MacIntyre" wrote in message
...

True...PC monitors seem to be a different story, in my experience.

And I'm mighty cautious of microwave ovens.

N

NSM wrote:
"Tom MacIntyre" wrote in message
...


True...PC monitors seem to be a different story, in my experience.


And I'm mighty cautious of microwave ovens.


I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?

A

I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?

A

Why is it that I feel the need to ask "Did it?"?

"Angrie.Woman" wrote in message
...

NSM wrote:
"Tom MacIntyre" wrote in message
...


True...PC monitors seem to be a different story, in my experience.


And I'm mighty cautious of microwave ovens.


I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?

If it does I'd fix it or toss it.

N

BrotherBart wrote:
I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?


A


Why is it that I feel the need to ask "Did it?"?



Yes...the last "real" job I had was for a telecommunications services
provider. They installed and maintained towers, as well as the cellular,
and microwave equipment, associated with all of it.

The guys used to do that to prove that the ovens weren't really all that
well insulated, but I always wondered if there was another reason that
might happen.
A

On Fri, 24 Jun 2005 16:04:45 -0400, "Rita Ä Berkowitz" ritaberk2O04
@aol.com wrote:

"NSM" wrote in message...

Any TV that's been sitting for a week won't have a charge in it.

BULL****! Put your tongue on the HV lead of the flyback transformer six
months after you unplugged it and you'll probably **** all over yourself if
you are lucky..



Rita


Been there..done that..still remember the spasms.. but I wasn't
stupid enough to use my tounge.

Fingers were quite enough.

Gunner

"Considering the events of recent years,
the world has a long way to go to regain
its credibility and reputation with the US."
unknown

In article ,
"Angrie.Woman" wrote:

NSM wrote:
"Tom MacIntyre" wrote in message
...


True...PC monitors seem to be a different story, in my experience.


And I'm mighty cautious of microwave ovens.


I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?

The shielding is not required to be perfect, cutting the ~600 watts RF
internal leftover-heating power to something like a milliwatt of leakage
per centimeter of door seal (I don't recall the exact number, but it
will be *somewhere* on the FCC website), which would be something like
100 milliwatts total leakage for a small door. The intent is only to
reduce the leakage to safe power levels; there will always be some
leakage.

Also, the seals on a microwave oven are only required to work at 2,450
MHz, while cellphones are more like 900 MHz, and some very good kinds of
door seals (choke seals) are tuned to a specific frequency, and so would
fail miserably at 1/3 the design frequency.

So, if you are close to a cellphone base station, one can imagine that
the phone inside the microwave could still hear the call and ring.

Joe Gwinn

Tom MacIntyre writes:

On Sat, 25 Jun 2005 01:25:45 GMT, "BrotherBart"
wrote:

If you've got no pride, just pick up anything but a TV (unless you know
how to discharge the cap) from the garbage and give it a go.

When I was five years old my dad was less than impressed when I took his
pocket watch apart.


BG

My dad was a very good backyard mechanic, but for some reason didn't
get into the more intricate stuff. One sunny summer Saturday morning,
I placed a sheet of plywood on the ground, removed the Carter BBD (I
think) carburator from the 225 slant-six motor in the 1965 Dodge
Polara station wagon he was preparing for the road, and stripped it
down on the sheet of plywood. My dad had worked a backshift, and at
about 1130 or so came outside, and turned white as a sheet. He said,
"Are you sure you can get that thing back together?" I assured him
that I could, and I did, and the car lived to ride again. :-)

I still don't understand why a man who could strip down a motor or
transmission, install new rings, valves, etc., had a problem with a
carburator...I couldn't rebuild a motor to save my own life, but I've
rebuilt a number of carburators...strange.

Because, as we all know, some parts of automotive carburetors run on
magic. And like the smoke sealed up inside working electronic components,
you really don't want to let it escape.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

Angrie.Woman wrote:
NSM wrote:

"Tom MacIntyre" wrote in message
...


True...PC monitors seem to be a different story, in my experience.



And I'm mighty cautious of microwave ovens.


I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?

A

Depends on the Poodle.


--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email:

Please visit my GURU's LAIR web site at http://www.tinaja.com

"Angrie.Woman" wrote in message
...

Yes...the last "real" job I had was for a telecommunications services
provider. They installed and maintained towers, as well as the cellular,
and microwave equipment, associated with all of it.

The guys used to do that to prove that the ovens weren't really all that
well insulated, but I always wondered if there was another reason that
might happen.

Thinking about that, the front has a pierced panel that blocks radiation at
around 2.5 gigahertz, however the cell phone runs at around 800 MHz so it's
possible enough of that frequency will leak through to make it work.

N

One time we were sending a bunch of CRT's back to the manufacturer for
proof-of- replacement one time, and my wife was labelling them. She
was wearing a knitted sweater, and the sleeve brushed against the 2nd
anode. She wasn't pleased with the result. The CRT had been sitting
for weeks to months...

Tom

A CRT that's not connected to the HV lead won't have any path to ground to
bleed the charge off, it'll pick up static from the air over time.

Joseph Gwinn wrote:
In article ,
"Angrie.Woman" wrote:


NSM wrote:

"Tom MacIntyre" wrote in message
...



True...PC monitors seem to be a different story, in my experience.


And I'm mighty cautious of microwave ovens.


I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?


The shielding is not required to be perfect, cutting the ~600 watts RF
internal leftover-heating power to something like a milliwatt of leakage
per centimeter of door seal (I don't recall the exact number, but it
will be *somewhere* on the FCC website), which would be something like
100 milliwatts total leakage for a small door. The intent is only to
reduce the leakage to safe power levels; there will always be some
leakage.

Also, the seals on a microwave oven are only required to work at 2,450
MHz, while cellphones are more like 900 MHz, and some very good kinds of
door seals (choke seals) are tuned to a specific frequency, and so would
fail miserably at 1/3 the design frequency.

So, if you are close to a cellphone base station, one can imagine that
the phone inside the microwave could still hear the call and ring.

Cool - thanks for the explanation!

A

That concept has been checked out by "Mythbusters" and found to be
essentially a myth.
Never the less I would check the direction before pointing.

"Christopher Tidy" wrote in message
...
JohnM wrote:

I've never considered ****ing all over myself to be a lucky thing..



I think the alternative is having your heart stop from the shock.

A


How about if I just don't put my tongue on electrical stuff, then I
won't have to be thankful for ****ing myself;-)

I think I just don't ever want to be thankful for that..

A while back I read in a tabloid about a man who had a nasty accident
after he left a bar drunken in the early hours. He was walking home with
a few mates when he needed to relieve himself. His mates dared him to
pee off the parapet of a railway bridge, which he did. Apparently his
stream of urine hit the 25 kV overhead wire which supplied the trains,
and he had a difficult job explaining the situation to a doctor at the
hospital when he came to.

Chris

Tom Miller wrote:

"Christopher Tidy" wrote in message
...

JohnM wrote:


I've never considered ****ing all over myself to be a lucky thing..



I think the alternative is having your heart stop from the shock.

A


How about if I just don't put my tongue on electrical stuff, then I
won't have to be thankful for ****ing myself;-)

I think I just don't ever want to be thankful for that..

A while back I read in a tabloid about a man who had a nasty accident
after he left a bar drunken in the early hours. He was walking home with
a few mates when he needed to relieve himself. His mates dared him to
pee off the parapet of a railway bridge, which he did. Apparently his
stream of urine hit the 25 kV overhead wire which supplied the trains,
and he had a difficult job explaining the situation to a doctor at the
hospital when he came to.

That concept has been checked out by "Mythbusters" and found to be
essentially a myth.
Never the less I would check the direction before pointing.

I suspected so. I imagine that if you peed from a height of more than a
few feet, the stream of urine would break up into droplets and would not
form the necessary conductive path. Still, I wouldn't want to try it
with 25 kV.

Chris

Tom Miller wrote:

"Christopher Tidy" wrote in message
...

JohnM wrote:


I've never considered ****ing all over myself to be a lucky thing..



I think the alternative is having your heart stop from the shock.

A


How about if I just don't put my tongue on electrical stuff, then I
won't have to be thankful for ****ing myself;-)

I think I just don't ever want to be thankful for that..

A while back I read in a tabloid about a man who had a nasty accident
after he left a bar drunken in the early hours. He was walking home with
a few mates when he needed to relieve himself. His mates dared him to
pee off the parapet of a railway bridge, which he did. Apparently his
stream of urine hit the 25 kV overhead wire which supplied the trains,
and he had a difficult job explaining the situation to a doctor at the
hospital when he came to.

That concept has been checked out by "Mythbusters" and found to be
essentially a myth.
Never the less I would check the direction before pointing.

I suspected so. I imagine that if you peed from a height of more than a
few feet, the stream of urine would break up into droplets and would not
form the necessary conductive path. Still, I wouldn't want to try it
with 25 kV.

Chris

I suspected so. I imagine that if you peed from a height of more than a
few feet, the stream of urine would break up into droplets and would not
form the necessary conductive path. Still, I wouldn't want to try it
with 25 kV.



Yeah on that chance that a solid stream did connect, pee is a pretty good
conductor of electricity, I know people who've accidently peed on electric
fences and I do know for a fact that it'll bite you.

"Christopher Tidy" wrote in message
...

I suspected so. I imagine that if you peed from a height of more than a
few feet, the stream of urine would break up into droplets and would not
form the necessary conductive path. Still, I wouldn't want to try it
with 25 kV.

In New Zealand they have interisland undersea lines which run at 500 KV DC
IIRC and they wash the salt off the insulators with a 'chopped' spray jet of
water. Scary job IMO.

N

On Sun, 26 Jun 2005 00:14:53 GMT, "James Sweet"
wrote:



I suspected so. I imagine that if you peed from a height of more than a
few feet, the stream of urine would break up into droplets and would not
form the necessary conductive path. Still, I wouldn't want to try it
with 25 kV.



Yeah on that chance that a solid stream did connect, pee is a pretty good
conductor of electricity, I know people who've accidently peed on electric
fences and I do know for a fact that it'll bite you.

Electric fence...been there..done that..still tend to curl into the
fetal position at the memory..

Gunner

"Considering the events of recent years,
the world has a long way to go to regain
its credibility and reputation with the US."
unknown

In sci.electronics.repair Tom Quackenbush wrote:
I had heard that it meant "frog in forest", or words to that
effect. The "forest" part makes sense, but maybe not the "frog" part.

Well, both ducks and frogs say 'quack', (kwak in dutch) so it could be
true.

Duck trapping wouldn't be such a bad profession, I guess. Sounds
better than "nightsoil collectors".

;-)

---
Met vriendelijke groet,

Maarten Bakker.

In article Lolve.107258$on1.101522@clgrps13, "NSM"
wrote:

"Angrie.Woman" wrote in message
...

Yes...the last "real" job I had was for a telecommunications services
provider. They installed and maintained towers, as well as the cellular,
and microwave equipment, associated with all of it.

The guys used to do that to prove that the ovens weren't really all that
well insulated, but I always wondered if there was another reason that
might happen.

Thinking about that, the front has a pierced panel that blocks radiation at
around 2.5 gigahertz, however the cell phone runs at around 800 MHz so it's
possible enough of that frequency will leak through to make it work.

It goes the other way: To get through the holes, the frequency would
need to be much higher than 2450 MHz.

The rule of thumb is that the wavelength of the radiation in question
must fit into a hole in the metal sheet. The higher the frequency, the
shorter the wavelength. The relevant equation is that the product of
frequency and wavelength equals the speed of light.

So, for 2450 MHz: (2450*10^6)(wavelength)=3*10^8 meters/second, so
wavelength= 0.122 meters, or 4.8 inches diameter. Actually, there will
be significant energy leaking through if a half wavelength fits, so the
issue really starts at about 2.4 inches. The cutoff function is
complicated near one wavelength.

Joe Gwinn

In article pBlve.5142$dY1.3431@trnddc06,
"James Sweet" wrote:

One time we were sending a bunch of CRT's back to the manufacturer for
proof-of- replacement one time, and my wife was labelling them. She
was wearing a knitted sweater, and the sleeve brushed against the 2nd
anode. She wasn't pleased with the result. The CRT had been sitting
for weeks to months...

Tom

A CRT that's not connected to the HV lead won't have any path to ground to
bleed the charge off, it'll pick up static from the air over time.

The issue with CRTs is that the glass dielectric, having been kept at
many tens of kilovolts for years, will store charge deep in the glass,
and this charge cannot be eliminated quickly. The phenomena is called
"dielectric adsorption" or "soakage". One can short such a CRT for a
week, remove the short, and see the voltage magically spring back. So
leave it shorted.

Big capacitors can do this as well, especially the big oil-paper
capacitors used in HV power supplies. These can store a lethal jolt.

This same phenomena is used in Electret microphones, where a thin layer
of teflon stores the HV charge needed to make the microphone work.

Joe Gwinn

On Sun, 26 Jun 2005 00:06:57 +0000 (UTC), Christopher Tidy
wrote:

Tom Miller wrote:

"Christopher Tidy" wrote in message
...

JohnM wrote:


I've never considered ****ing all over myself to be a lucky thing..



I think the alternative is having your heart stop from the shock.

A


How about if I just don't put my tongue on electrical stuff, then I
won't have to be thankful for ****ing myself;-)

I think I just don't ever want to be thankful for that..

A while back I read in a tabloid about a man who had a nasty accident
after he left a bar drunken in the early hours. He was walking home with
a few mates when he needed to relieve himself. His mates dared him to
pee off the parapet of a railway bridge, which he did. Apparently his
stream of urine hit the 25 kV overhead wire which supplied the trains,
and he had a difficult job explaining the situation to a doctor at the
hospital when he came to.

That concept has been checked out by "Mythbusters" and found to be
essentially a myth.
Never the less I would check the direction before pointing.

I suspected so. I imagine that if you peed from a height of more than a
few feet, the stream of urine would break up into droplets and would not
form the necessary conductive path. Still, I wouldn't want to try it
with 25 kV.

Chris

What is the arc distance for dry air, 12kV per inch or something like
that? I definitely wouldn't be trying it with 25kV. :-)

Tom

On Sat, 25 Jun 2005 19:13:16 GMT, "Angrie.Woman"
wrote:

NSM wrote:
"Tom MacIntyre" wrote in message
...


True...PC monitors seem to be a different story, in my experience.


And I'm mighty cautious of microwave ovens.


I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?

A

For my wife's Diplomat microwave oven and my Nokia cellular telephone,
the answer is yes. :-)

Tom

On Sat, 25 Jun 2005 20:25:25 GMT, "Angrie.Woman"
wrote:

BrotherBart wrote:
I have a question. If I put a cellphone in a microwave oven, close the
door, call the number....should it ring?


A


Why is it that I feel the need to ask "Did it?"?



Yes...the last "real" job I had was for a telecommunications services
provider. They installed and maintained towers, as well as the cellular,
and microwave equipment, associated with all of it.

The guys used to do that to prove that the ovens weren't really all that
well insulated, but I always wondered if there was another reason that
might happen.
A

They are probably well-insulated for their own particular frequency.

Tom

On Sun, 26 Jun 2005 10:25:57 -0400, Joseph Gwinn
wrote:

In article pBlve.5142$dY1.3431@trnddc06,
"James Sweet" wrote:

One time we were sending a bunch of CRT's back to the manufacturer for
proof-of- replacement one time, and my wife was labelling them. She
was wearing a knitted sweater, and the sleeve brushed against the 2nd
anode. She wasn't pleased with the result. The CRT had been sitting
for weeks to months...

Tom

A CRT that's not connected to the HV lead won't have any path to ground to
bleed the charge off, it'll pick up static from the air over time.

The issue with CRTs is that the glass dielectric, having been kept at
many tens of kilovolts for years, will store charge deep in the glass,
and this charge cannot be eliminated quickly. The phenomena is called
"dielectric adsorption" or "soakage". One can short such a CRT for a
week, remove the short, and see the voltage magically spring back. So
leave it shorted.

Dielectric absorption is one of the factors that the Sencore LC line
of capacitor/inductor testers measures. Thanks.

Tom


Big capacitors can do this as well, especially the big oil-paper
capacitors used in HV power supplies. These can store a lethal jolt.

This same phenomena is used in Electret microphones, where a thin layer
of teflon stores the HV charge needed to make the microphone work.

Joe Gwinn

Angrie.Woman wrote:

Koz wrote:




I know that old printers/copiers are cheap as dirt (free often) and
can be used the same way, although they don't have quite as many parts
as those old calculators. I've had my daughter take apart a couple of
similar things as a learning experience (help dad by salvaging parts).
Any other ideas on cheap mechanical junk that is readily available and
may be a great learning experience for the mechanical kid to monkey
around with?

Koz



Anything. My #1 son is a "take apart junkie." he takes his wagon out
bright and early every monday morning to find stuff to bring home and
dismantle. We've done toasters, VCR's, tape recorders, toys - all kinds
of stuff. Last week we did an aqua-pic and a hose sprayer that had an
adjustable flow thingy. A 35mm camera was cool - about a gazillion parts
crammed into a 3 x 5" box. Amazing to me, who can't seem to even fit all
our clothes into the closet.

If you've got no pride, just pick up anything but a TV (unless you know
how to discharge the cap) from the garbage and give it a go.



A
TV discharge is easy. A stick with a nail in the end, that has a wire
attached that is 'clipped' to the metal chassis. The nail is (when holding the
wood stick - and insulated nicely (broom stick...) is slid under the HV plug.
The arc will be under the plug cap and should be heard. e.g. if not - try again
and wiggle around. Once done, or decided not needed - then the nail on stick
is used (still attached - just in case) - and is hammered - slightly - through
the metal seal that serves as the high voltage connector. Air flow will follow.
Allow a slow flow. Breaking rapidly might implode the 'tube' end through the screen.
So that is the reason to punch it with a nail. (or punch...)

Naturally, it is a hasmat item - lead in the glass, phosphor in the screen, metals in
the metals... Best to be left alone.

Martin

--
Martin Eastburn
@ home at Lion's Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

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NSM wrote:
"Christopher Tidy" wrote in message
...

I suspected so. I imagine that if you peed from a height of more
than a few feet, the stream of urine would break up into droplets
and would not form the necessary conductive path. Still, I wouldn't
want to try it with 25 kV.

In New Zealand they have interisland undersea lines which run at 500
KV DC IIRC and they wash the salt off the insulators with a 'chopped'
spray jet of water. Scary job IMO.

N

I remember getting 'bitten' by an electric fence on which I played a stream
of water from a garden hose, as a kid. The charger was the 'pulsed' type
which used a 6v battery, inductor and 'balance beam' switcher for power.
The hose had no nozzle on it, so I was using my finger to direct the spray.
The distance was only a few feet, and the jolt was roughly comparable to
touching the fence directly--it was never too effective even with direct
contact...

jak