Discuss

Not in its current state, when the cost of repairing an item is comparable
to the cost of a new one.

"N_Cook" wrote in message
...
Discuss

I assume you meant commercial repair of consumer goods. If so, my feeling
is Yes, but to a limited degree. I doubt that repair shops will see much
more than a 5% increase in actual volume (those customers who opt to
actually have it repaired). There will be more inquiries. The low-end
stuff will remain in the throw-away category and the high-end stuff is
mostly already covered by extended warranties (which most consumers opt
for).

Charles wrote in message
. ..


"N_Cook" wrote in message
...
Discuss

I assume you meant commercial repair of consumer goods. If so, my feeling
is Yes, but to a limited degree. I doubt that repair shops will see much
more than a 5% increase in actual volume (those customers who opt to
actually have it repaired). There will be more inquiries. The low-end
stuff will remain in the throw-away category and the high-end stuff is
mostly already covered by extended warranties (which most consumers opt
for).



There is a price breakpoint , that varies from owner to owner (company or
individual). Cost to repair versus cost to replace, so a ratio.
I would assume that breakpoint ratio moves towards favouring repair in
resession.
Also assuming some degree of essentiality that would also vary with degree
of resession.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N_Cook" wrote in message
...
Charles wrote in message
. ..


"N_Cook" wrote in message
...
Discuss

I assume you meant commercial repair of consumer goods. If so, my
feeling
is Yes, but to a limited degree. I doubt that repair shops will see much
more than a 5% increase in actual volume (those customers who opt to
actually have it repaired). There will be more inquiries. The low-end
stuff will remain in the throw-away category and the high-end stuff is
mostly already covered by extended warranties (which most consumers opt
for).



There is a price breakpoint , that varies from owner to owner (company or
individual). Cost to repair versus cost to replace, so a ratio.
I would assume that breakpoint ratio moves towards favouring repair in
resession.
Also assuming some degree of essentiality that would also vary with degree
of resession.


So you might think, but in my experience, particularly with companies, there
are many factors other than price, which drive the decision making process.
For instance, one place that I was until a few months ago, repairing large
volumes of a particular board for, has been taken over by another company. I
was charging them 30 quid a pop to repair them. They are currently buying in
new boards from the manufacturer, at 150 quid a time, and throwing the
faulty ones away ! (I know this for a fact, as I know someone that works for
them). The best of it is that as a part of the repair, I used to carry out a
reliability mod, that made them virtually indestructible after it had been
carried out. So here we are hovering on the edge of recession, and you would
think that a saving of 120 quid a board, and a reduction in your field
service call-back rate, would be just what the doctor ordered, but no. For
reasons best known to themselves, they throw money away. So how do you
reconcile that one ?

Just as an aside. I know how much you love valves ... Today, I had a
Marshall on the bench. Pair of EL34s in the output. On the tester, it
sounded awful, and the 'scope showed a highly assymetric output waveform.
The drive to both outputs was fine, and the bias was correct on both valves.
The waveforms on the anode of each valve looked pretty similar, but on the
back side of the output tranny, it looked lousy. Both valves had screen
voltage, fed via a 1k resistor each, but I noticed that the screen volts at
the actual pin was 4 volts lower on one valve, than the other. When I
measured actually across each screenfeed R, one of them had 4.4 volts across
it, and the other had nothing. Turned out that the screen grid was open
circuit on that valve. I hung a test one in there, and the voltage drop
reappeared as it should, and the waveform on the output was now perfect. A
new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think that
I can remember ever having had an open circuit screen grid.

Arfa

On 4/16/08 11:02 AM, in article ,
"Arfa Daily" wrote:


"N_Cook" wrote in message
...
Charles wrote in message
. ..


"N_Cook" wrote in message
...
Discuss

I assume you meant commercial repair of consumer goods. If so, my
feeling
is Yes, but to a limited degree. I doubt that repair shops will see much
more than a 5% increase in actual volume (those customers who opt to
actually have it repaired). There will be more inquiries. The low-end
stuff will remain in the throw-away category and the high-end stuff is
mostly already covered by extended warranties (which most consumers opt
for).



There is a price breakpoint , that varies from owner to owner (company or
individual). Cost to repair versus cost to replace, so a ratio.
I would assume that breakpoint ratio moves towards favouring repair in
resession.
Also assuming some degree of essentiality that would also vary with degree
of resession.


So you might think, but in my experience, particularly with companies, there
are many factors other than price, which drive the decision making process.
For instance, one place that I was until a few months ago, repairing large
volumes of a particular board for, has been taken over by another company. I
was charging them 30 quid a pop to repair them. They are currently buying in
new boards from the manufacturer, at 150 quid a time, and throwing the
faulty ones away ! (I know this for a fact, as I know someone that works for
them). The best of it is that as a part of the repair, I used to carry out a
reliability mod, that made them virtually indestructible after it had been
carried out. So here we are hovering on the edge of recession, and you would
think that a saving of 120 quid a board, and a reduction in your field
service call-back rate, would be just what the doctor ordered, but no. For
reasons best known to themselves, they throw money away. So how do you
reconcile that one ?

Probably by looking at the real costs of you doing a repair job versus the
cost of having a non-technical person simply exchange boards. Also, the new
board would have a sizeable markup. Some companies just don't consider what
is fair and reasonable, wanting only to maximize profits at the customer and
employee's expense.


Just as an aside. I know how much you love valves ... Today, I had a
Marshall on the bench. Pair of EL34s in the output. On the tester, it
sounded awful, and the 'scope showed a highly assymetric output waveform.
The drive to both outputs was fine, and the bias was correct on both valves.
The waveforms on the anode of each valve looked pretty similar, but on the
back side of the output tranny, it looked lousy. Both valves had screen
voltage, fed via a 1k resistor each, but I noticed that the screen volts at
the actual pin was 4 volts lower on one valve, than the other. When I
measured actually across each screenfeed R, one of them had 4.4 volts across
it, and the other had nothing. Turned out that the screen grid was open
circuit on that valve. I hung a test one in there, and the voltage drop
reappeared as it should, and the waveform on the output was now perfect. A
new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think that
I can remember ever having had an open circuit screen grid.

Arfa

On Apr 15, 1:31 pm, "N_Cook" wrote:
Discuss

http://www.youtube.com/watch?v=ap0-SCwi89U

;-)

regards,
B-

"Don Bowey" wrote in message
...
On 4/16/08 11:02 AM, in article
,
"Arfa Daily" wrote:


"N_Cook" wrote in message
...
Charles wrote in message
. ..


"N_Cook" wrote in message
...
Discuss

I assume you meant commercial repair of consumer goods. If so, my
feeling
is Yes, but to a limited degree. I doubt that repair shops will see
much
more than a 5% increase in actual volume (those customers who opt to
actually have it repaired). There will be more inquiries. The low-end
stuff will remain in the throw-away category and the high-end stuff is
mostly already covered by extended warranties (which most consumers opt
for).



There is a price breakpoint , that varies from owner to owner (company
or
individual). Cost to repair versus cost to replace, so a ratio.
I would assume that breakpoint ratio moves towards favouring repair in
resession.
Also assuming some degree of essentiality that would also vary with
degree
of resession.


So you might think, but in my experience, particularly with companies,
there
are many factors other than price, which drive the decision making
process.
For instance, one place that I was until a few months ago, repairing
large
volumes of a particular board for, has been taken over by another
company. I
was charging them 30 quid a pop to repair them. They are currently buying
in
new boards from the manufacturer, at 150 quid a time, and throwing the
faulty ones away ! (I know this for a fact, as I know someone that works
for
them). The best of it is that as a part of the repair, I used to carry
out a
reliability mod, that made them virtually indestructible after it had
been
carried out. So here we are hovering on the edge of recession, and you
would
think that a saving of 120 quid a board, and a reduction in your field
service call-back rate, would be just what the doctor ordered, but no.
For
reasons best known to themselves, they throw money away. So how do you
reconcile that one ?

Probably by looking at the real costs of you doing a repair job versus the
cost of having a non-technical person simply exchange boards. Also, the
new
board would have a sizeable markup. Some companies just don't consider
what
is fair and reasonable, wanting only to maximize profits at the customer
and
employee's expense.


Perhaps I'm a bit thick tonight Don, but I'm not quite following the logic
of that one ! The 'real' cost of me doing a repair to one of their boards is
30 quid. Their field engineers replace boards at the customer site from
their van stock. The machines that these boards go in are supplied to the
end user F.O.C. , the money being made on supplied product for use in that
machine. So there is no repair cost to the customer. The field engineer
returns the faulty board to stores, and a spotty faced youth collects them
up until he has a batch, and then sends them to me. I duly repair them, and
relieve them of 30 quid per board. Fixed price. No hidden charges. 30 quid.
That's it.

Now, instead of the SFY batching them up and sending them to me, he is
batching them up, and flinging them in the dumpster. In the meantime, they
are buying in new boards from the company that make the machines, and paying
150 quid each for them. No discounts. No cost percentage recovered from the
end user. No offset at all. So that's 150 quid per board, per field repair
that uses one, sitting on their books, as opposed to 30 quid per board per
field repair if they use me to repair them. That's 120 quid of 'real' cost
coming out of their pockets. So explain to me again how that is a better
deal for them ... :-)

Arfa

"Arfa Daily" wrote in news:ShxNj.4786$DQ3.3407
@newsfe1-win.ntli.net:

So explain to me again how that is a better
deal for them ...

When I had my repair shop I found that 'if the repair cost less than 1/3
the cost of a new unit, they usually fixed it'.

On the other hand, if they could buy a new one for less than 3 times the
repair cost, I was going to end up owning a repaired set, even if they said
'go ahead and fix it'.

I doubt that people have changed much since I closed my shop.

Note: often to 'estimate' the costs of the repair, it was necessary to fix
the danged set, and then 'unfix it' if they declined the repair but wanted
to pick up the broken set.
That was ONE of several reasons I closed my shop in the early 70's.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

bz wrote in message
98.139...
"Arfa Daily" wrote in news:ShxNj.4786$DQ3.3407
@newsfe1-win.ntli.net:

So explain to me again how that is a better
deal for them ...

When I had my repair shop I found that 'if the repair cost less than 1/3
the cost of a new unit, they usually fixed it'.

On the other hand, if they could buy a new one for less than 3 times the
repair cost, I was going to end up owning a repaired set, even if they
said
'go ahead and fix it'.

I doubt that people have changed much since I closed my shop.

Note: often to 'estimate' the costs of the repair, it was necessary to fix
the danged set, and then 'unfix it' if they declined the repair but wanted
to pick up the broken set.
That was ONE of several reasons I closed my shop in the early 70's.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

For newcomers I always charge an upfront "exploration fee" of 8GBP/15USD to
15GBP/30USD, mainly dependent on size, and get back to them by phone or
email with some sort of quote for repair, if its a diagnostic repair rather
than replacing a mains switch type repair. I can never give a quote ,
unseen, inside the kit.
It avoids total timewasters and gives them a chance to drop out at an earkly
stage, but I've not wasted the time of getting inside, etc.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N_Cook" wrote in
:

.....
For newcomers I always charge an upfront "exploration fee" of 8GBP/15USD
to 15GBP/30USD, mainly dependent on size, and get back to them by phone
or email with some sort of quote for repair, if its a diagnostic repair
rather than replacing a mains switch type repair. I can never give a
quote , unseen, inside the kit.
It avoids total timewasters and gives them a chance to drop out at an
earkly stage, but I've not wasted the time of getting inside, etc.

Yep. We always charged $25 checkout fee, UP FRONT, to look at the set.

That was applied to the repairs, if they decided to repair the set.





--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

N_Cook wrote:
For newcomers I always charge an upfront "exploration fee" of 8GBP/15USD to
15GBP/30USD, mainly dependent on size, and get back to them by phone or
email with some sort of quote for repair, if its a diagnostic repair rather
than replacing a mains switch type repair. I can never give a quote ,
unseen, inside the kit.

Didn't ASDA have DVD players around Christmas for 10 quid? At that price,
you are not going to see many in for an 8 quid estimate.

With prices like that, people are just going to buy a cheap new one instead
of paying you to fix their old one, no matter how much better it was.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM

On Apr 16, 2:02*pm, "Arfa Daily" wrote:
Just as an aside. I know how much you love valves ... *Today, I had a
Marshall on the bench. Pair of EL34s in the output. On the tester, it
sounded awful, and the 'scope showed a highly assymetric output waveform.
The drive to both outputs was fine, and the bias was correct on both valves.
The waveforms on the anode of each valve looked pretty similar, but on the
back side of the output tranny, it looked lousy. Both valves had screen
voltage, fed via a 1k resistor each, but I noticed that the screen volts at
the actual pin was 4 volts lower on one valve, than the other. When I
measured actually across each screenfeed R, one of them had 4.4 volts across
it, and the other had nothing. Turned out that the screen grid was open
circuit on that valve. I hung a test one in there, and the voltage drop
reappeared as it should, and the waveform on the output was now perfect. A
new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think that
I can remember ever having had an open circuit screen grid.

Arfa

Screen failures are more common with the newer production tubes/
valves. Its either mechanical stress or over dissapation that kills
'em.

"boardjunkie" wrote in message
...
On Apr 16, 2:02 pm, "Arfa Daily" wrote:
Just as an aside. I know how much you love valves ... Today, I had a
Marshall on the bench. Pair of EL34s in the output. On the tester, it
sounded awful, and the 'scope showed a highly assymetric output waveform.
The drive to both outputs was fine, and the bias was correct on both
valves.
The waveforms on the anode of each valve looked pretty similar, but on the
back side of the output tranny, it looked lousy. Both valves had screen
voltage, fed via a 1k resistor each, but I noticed that the screen volts
at
the actual pin was 4 volts lower on one valve, than the other. When I
measured actually across each screenfeed R, one of them had 4.4 volts
across
it, and the other had nothing. Turned out that the screen grid was open
circuit on that valve. I hung a test one in there, and the voltage drop
reappeared as it should, and the waveform on the output was now perfect. A
new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think
that
I can remember ever having had an open circuit screen grid.

Arfa

Screen failures are more common with the newer production tubes/
valves. Its either mechanical stress or over dissapation that kills
'em.

It was a fairly 'new' tube as in 8 years or so, but an original Marshall
factory fit. As far as you could see looking through the glass, it was a
'genuine' EL34 pentode, rather than a 6L6 look-alike beam tetrode
masquerading as an EL34. The screen grid connection ribbon looked intact.
Just for sport, I tried measuring the capacitance from the screen grid to
the anode, and it measured exactly the same as on the opposite tube which
was working, so that would indicate that the screen was in fact intact.
Never-the-less, the bad tube drew no discernible screen current at all. The
emission was pretty poor on both tubes, so about the only other thing that I
can come up with is that the emission was so low on that tube, that the
standing bias had it basically cut off, so the screen had no source of
current to draw from.

Arfa

On Wed, 16 Apr 2008 18:02:12 GMT, "Arfa Daily"
put finger to keyboard and composed:

So you might think, but in my experience, particularly with companies, there
are many factors other than price, which drive the decision making process.
For instance, one place that I was until a few months ago, repairing large
volumes of a particular board for, has been taken over by another company. I
was charging them 30 quid a pop to repair them. They are currently buying in
new boards from the manufacturer, at 150 quid a time, and throwing the
faulty ones away ! (I know this for a fact, as I know someone that works for
them). The best of it is that as a part of the repair, I used to carry out a
reliability mod, that made them virtually indestructible after it had been
carried out. So here we are hovering on the edge of recession, and you would
think that a saving of 120 quid a board, and a reduction in your field
service call-back rate, would be just what the doctor ordered, but no. For
reasons best known to themselves, they throw money away. So how do you
reconcile that one ?

I often had the reverse experience. Many large companies with
convoluted accounting practices would find it easier to repair
something by replacing a board costing $200 instead of requisitioning
an entire new unit costing, say, $100.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

"Franc Zabkar" wrote in message
...
On Wed, 16 Apr 2008 18:02:12 GMT, "Arfa Daily"
put finger to keyboard and composed:

So you might think, but in my experience, particularly with companies,
there
are many factors other than price, which drive the decision making
process.
For instance, one place that I was until a few months ago, repairing large
volumes of a particular board for, has been taken over by another company.
I
was charging them 30 quid a pop to repair them. They are currently buying
in
new boards from the manufacturer, at 150 quid a time, and throwing the
faulty ones away ! (I know this for a fact, as I know someone that works
for
them). The best of it is that as a part of the repair, I used to carry out
a
reliability mod, that made them virtually indestructible after it had been
carried out. So here we are hovering on the edge of recession, and you
would
think that a saving of 120 quid a board, and a reduction in your field
service call-back rate, would be just what the doctor ordered, but no. For
reasons best known to themselves, they throw money away. So how do you
reconcile that one ?

I often had the reverse experience. Many large companies with
convoluted accounting practices would find it easier to repair
something by replacing a board costing $200 instead of requisitioning
an entire new unit costing, say, $100.

- Franc Zabkar

Yes Franc. Bizarre isn't it ? I don't think that we will ever understand the
convoluted thinking that goes on in big business, because being service
people, we are basically practical and 'linear' thinkers. Seeing the 'bigger
picture' is not something that engineers are good at, in my experience.
Probably as a result of our job and training taking us down an ever narrower
field of view towards our goal of finding the single component, or small
group of components, that's at fault.

I like to think of myself as a "man in business", rather than a
"businessman".

Arfa

Arfa Daily wrote:

Just as an aside. I know how much you love valves ... Today, I had a
Marshall on the bench. Pair of EL34s in the output. On the tester, it
sounded awful, and the 'scope showed a highly assymetric output waveform.
The drive to both outputs was fine, and the bias was correct on both valves.
The waveforms on the anode of each valve looked pretty similar, but on the
back side of the output tranny, it looked lousy. Both valves had screen
voltage, fed via a 1k resistor each, but I noticed that the screen volts at
the actual pin was 4 volts lower on one valve, than the other. When I
measured actually across each screenfeed R, one of them had 4.4 volts across
it, and the other had nothing. Turned out that the screen grid was open
circuit on that valve. I hung a test one in there, and the voltage drop
reappeared as it should, and the waveform on the output was now perfect. A
new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think that
I can remember ever having had an open circuit screen grid.

Can't say I have either. But then again have you ever seen 4 output valves go
zero emission (this was in a Fender Twin Reverb). They were those dreadful Z&I
Aero Services (Zaerix) Russian valves from the 70s/80s. Quite bizarre, all drive
waveforms and bias voltages correct but no output at all.

Incidentally I got it working because it was needed urgently by fitting 4 EL34s
(I didn't have any 6L6s - you didn't see them much in the UK in those days).

Graham

N_Cook wrote:

Discuss

Most stuff isn't designed to be easily repairable any more and replacing
is so cheap that the question is largely moot.

Graham

On Apr 18, 8:44*pm, "Arfa Daily" wrote:
It was a fairly 'new' tube as in 8 years or so, but an original Marshall
factory fit.

By new production I meant anything Russian, China, etc. made these
days since tube production started shutting down in the 70s. The
Slovak made "JJ" branded pwr tubes are very robust. I'll normally use
them unless a customer specifies otherwise.


As far as you could see looking through the glass, it was a
'genuine' EL34 pentode, rather than a 6L6 look-alike beam tetrode
masquerading as an EL34.

That would be a 6CA7. Some ppl prefer the 6CA7 to EL34s in Mar$halls.
They're less "furry" sounding, kinda like a KT88's younger sibling.
Original Sylvania 6CA7s can bring impressive money these days for NOS.


The screen grid connection ribbon looked intact.
Just for sport, I tried measuring the capacitance from the screen grid to
the anode, and it measured exactly the same as on the opposite tube which
was working, so that would indicate that the screen was in fact intact.
Never-the-less, the bad tube drew no discernible screen current at all. The
emission was pretty poor on both tubes, so about the only other thing that I
can come up with is that the emission was so low on that tube, that the
standing bias had it basically cut off, so the screen had no source of
current to draw from.

Arfa- Hide quoted text -

- Show quoted text -

"boardjunkie" wrote in message
...
On Apr 18, 8:44 pm, "Arfa Daily" wrote:
It was a fairly 'new' tube as in 8 years or so, but an original Marshall
factory fit.

By new production I meant anything Russian, China, etc. made these
days since tube production started shutting down in the 70s. The
Slovak made "JJ" branded pwr tubes are very robust. I'll normally use
them unless a customer specifies otherwise.


As far as you could see looking through the glass, it was a
'genuine' EL34 pentode, rather than a 6L6 look-alike beam tetrode
masquerading as an EL34.


That would be a 6CA7. Some ppl prefer the 6CA7 to EL34s in Mar$halls.
They're less "furry" sounding, kinda like a KT88's younger sibling.
Original Sylvania 6CA7s can bring impressive money these days for NOS.

It was a genuine EL34 as in that's what it's marked, but not all tubes
marked EL34 are actually that inside, so I've read, although I don't usually
look that close, when I replace them. An article that I saw on Wiki a while
back, said that they were quite often actually beam tetrode electrode
assemblies, not genuine pentodes with a wire suppressor grid, even though
they were marked "EL34", so I guess that some 6CA7's might turn up marked as
EL34s. Just dug it out the trash to have a look, and there's no place of
origin on it, but I would guess that it's an eastern bloc job rather than a
Chinee.

Arfa

"Eeyore" wrote in message
...


Arfa Daily wrote:

Just as an aside. I know how much you love valves ... Today, I had a
Marshall on the bench. Pair of EL34s in the output. On the tester, it
sounded awful, and the 'scope showed a highly assymetric output waveform.
The drive to both outputs was fine, and the bias was correct on both
valves.
The waveforms on the anode of each valve looked pretty similar, but on
the
back side of the output tranny, it looked lousy. Both valves had screen
voltage, fed via a 1k resistor each, but I noticed that the screen volts
at
the actual pin was 4 volts lower on one valve, than the other. When I
measured actually across each screenfeed R, one of them had 4.4 volts
across
it, and the other had nothing. Turned out that the screen grid was open
circuit on that valve. I hung a test one in there, and the voltage drop
reappeared as it should, and the waveform on the output was now perfect.
A
new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think
that
I can remember ever having had an open circuit screen grid.

Can't say I have either. But then again have you ever seen 4 output valves
go
zero emission (this was in a Fender Twin Reverb). They were those dreadful
Z&I
Aero Services (Zaerix) Russian valves from the 70s/80s. Quite bizarre, all
drive
waveforms and bias voltages correct but no output at all.

Incidentally I got it working because it was needed urgently by fitting 4
EL34s
(I didn't have any 6L6s - you didn't see them much in the UK in those
days).

Graham

Yes Graham, I too have fitted 6L6's and vice versa. I have read on Wiki I
think that EL34's turn up with 6L6 guts in them. I think that the beam
tetrode structure was actually created to get around the patent that MO had
on the EL34 pentode structure, so I guess it's reasonable that they should
have similar characteristics. Crikey ! Z & I Aero Services aka Zaerix. That
takes me back a bit. I still have a Zaerix shortform catalogue in pristine
condition. Had some useful data in it, and ex military valves and 'scope /
radar tubes ...

Arfa

N_Cook wrote:

I would assume that breakpoint ratio moves towards favouring repair in
resession.
Only if wages drop or supply of replacements are affected.

Someone was recently explaining that his job was really to disconnect
the faulty module and connect the replacement module as everything in
his mine was now "modularised" and encapsulated. Final act was to put
the faulty part in the bin.

Arfa Daily wrote:

"Eeyore" wrote
Arfa Daily wrote:

A new pair of valves and a bias check finished the job off. How unusual a
problem is that ? In all my years of working with valves, I don't think
that I can remember ever having had an open circuit screen grid.

Can't say I have either. But then again have you ever seen 4 output valves
go zero emission (this was in a Fender Twin Reverb). They were those
dreadful
Z&I Aero Services (Zaerix) Russian valves from the 70s/80s. Quite bizarre,
all
drive waveforms and bias voltages correct but no output at all.

Incidentally I got it working because it was needed urgently by fitting 4
EL34s (I didn't have any 6L6s - you didn't see them much in the UK in those
days).

Graham

Yes Graham, I too have fitted 6L6's and vice versa. I have read on Wiki I
think that EL34's turn up with 6L6 guts in them. I think that the beam
tetrode structure was actually created to get around the patent that MO had
on the EL34 pentode structure

I think you're right about that although the patent would have been on the KT66
I think. MOV never made the EL34 AFAIK.


so I guess it's reasonable that they should
have similar characteristics. Crikey ! Z & I Aero Services aka Zaerix. That
takes me back a bit. I still have a Zaerix shortform catalogue in pristine
condition. Had some useful data in it, and ex military valves and 'scope /
radar tubes ...

I recall their shop in Tottenham Court Road too. You could still browse surplus
equipment back in those days. Imagine what those properties must be worth now !

Graham