Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?

The polished stainless steel control panel has the legends only silk screen
printed on. No more durable than the white markings on valves/tubes. On/Off
and standby legends already worn off.
What is the recognised way of ameliorating this, remove pots etc, clean off
panel with very weak solvent and spray varnish over ?

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

N Cook wrote:
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?


Do you mean R97? 1.6k 2 watt?


Ron(UK)

Ron(UK) wrote in message
...
N Cook wrote:
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?


Do you mean R97? 1.6k 2 watt?


Ron(UK)

Yes, i was reading it upside down , goes to tip of footswitch plug, but I
would call it a 1W, when I replace it, it will be bigger.
Not the main problem which is drop in gain and distortion intermittently


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

N Cook wrote:
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?

The polished stainless steel control panel has the legends only silk screen
printed on. No more durable than the white markings on valves/tubes. On/Off
and standby legends already worn off.
What is the recognised way of ameliorating this, remove pots etc, clean off
panel with very weak solvent and spray varnish over ?

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





There is a repository of guitar amp schematics on the web, including
most of the vintage Fender models, including their many revisions.
Google would probably pull it up, or I might have bookmarked it. I'll
check....

jak

jakdedert wrote:
N Cook wrote:
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?

The polished stainless steel control panel has the legends only silk
screen
printed on. No more durable than the white markings on valves/tubes.
On/Off
and standby legends already worn off.
What is the recognised way of ameliorating this, remove pots etc,
clean off
panel with very weak solvent and spray varnish over ?

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





There is a repository of guitar amp schematics on the web, including
most of the vintage Fender models, including their many revisions.
Google would probably pull it up, or I might have bookmarked it. I'll
check....


This is a good site for diags

http://blueguitar.org/schems.htm

Ron(UK)

Ron(UK) wrote:
jakdedert wrote:
N Cook wrote:
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?

The polished stainless steel control panel has the legends only silk
screen
printed on. No more durable than the white markings on valves/tubes.
On/Off
and standby legends already worn off.
What is the recognised way of ameliorating this, remove pots etc,
clean off
panel with very weak solvent and spray varnish over ?

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





There is a repository of guitar amp schematics on the web, including
most of the vintage Fender models, including their many revisions.
Google would probably pull it up, or I might have bookmarked it. I'll
check....


This is a good site for diags

http://blueguitar.org/schems.htm

Ron(UK)

Indeed it is. I don't think it was the one to which I
referred...possibly even better!

jak

The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp input I
would not expect the output to be on the uncomfortable side of listening to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?

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

N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp input I
would not expect the output to be on the uncomfortable side of listening to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?

Have you tried it with a guitar?

Ron

Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp input
I
would not expect the output to be on the uncomfortable side of listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?

Have you tried it with a guitar?

Ron

Nope, I've always intended picking up a magnetic pick up from somewhere but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the norm
for just speaker output signal monitoring purposes, rather than dummy load
checking

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

N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp input
I
would not expect the output to be on the uncomfortable side of listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?

Ron

Nope, I've always intended picking up a magnetic pick up from somewhere but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the norm
for just speaker output signal monitoring purposes, rather than dummy load
checking

How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.

Do you have a typical stage microphone to test PA amps?

Ron

Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?

Ron

Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking

How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.

Do you have a typical stage microphone to test PA amps?

Ron

Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.

I have quite enough clutter here without a guitar as a test instrument and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.


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

N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?

Ron
Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking
How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.

Do you have a typical stage microphone to test PA amps?

Ron

Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.

I have quite enough clutter here without a guitar as a test instrument and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.

Don't you understand that striving for a clean distortion free sound
isnt right with a lot of guitar amps? A perfect waveform doesn't give
the sound a player might want. It`s the distortion that gives them their
characteristic sound. Setting up the bias for example - the technically
correct bias isnt necessarily the right bias (if you get my drift) They
aren't hifi amps, they are designed to colour the sound the way a
guitarist likes.

Ron

"N Cook" wrote in message
...
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp input I
would not expect the output to be on the uncomfortable side of listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?

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





Your measurements mean nothing in a guitar valve amp. They are designed to
distort. A Lot.

1. Put a sine wave at around 400 Hz into the power amp in jack, use a dummy
load, set the bias with a scope, measure the power output and observe the
waveform to make sure its not far off what it should be. Thats your power
amp working then.

2. Plug in a guitar and play it. If you can't hear anything amiss or don't
know what you should be listening for then don't bother trying to fix valve
guitar amps, or you'll be going round in circles measuring things, wondering
why there is so much distortion and the frequency response isn't very flat
at all.

3. If you are going to be fixing valve amps you need a stock of valves.
Best bet is to change the whole lot to a set you know works, then go through
the amp fixing any faults. Then go back and fit the originals, changing any
that are bad.



Gareth.

"Ron(UK)" wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?

Ron
Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking
How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.

Do you have a typical stage microphone to test PA amps?

Ron

Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.

I have quite enough clutter here without a guitar as a test instrument
and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.

Don't you understand that striving for a clean distortion free sound isnt
right with a lot of guitar amps? A perfect waveform doesn't give the sound
a player might want. It`s the distortion that gives them their
characteristic sound. Setting up the bias for example - the technically
correct bias isnt necessarily the right bias (if you get my drift) They
aren't hifi amps, they are designed to colour the sound the way a
guitarist likes.

Ron

As you say Ron, part of a valve amp's sound is the fact that it can be made
to go smoothly dirty, and often even has a channel designed to do just that
by deliberately overloading the second or third stage with pre and post gain
controls. I always think of the old Canned Heat number 'Let's Work Together'
as a premium example of how a guitar sound can be horrendously distorted,
whilst still being sufficiently musical to find its place in the song. I've
no idea as to whether that guitar was pre-processed with a fuzz pedal, but I
have heard stage musicians get a similar sound from just making use of the
overdrive facilities on their amp. 100mV does sound like a lot of input
compared to a guitar pickup, though. About the maximum that I normally drive
these things with, is 20mV.

Arfa

On Mar 18, 11:28*am, "Ron(UK)" wrote:
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?

Ron
Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking
How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.

Do you have a typical stage microphone to test PA amps?

Ron

Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.

I have quite enough clutter here without a guitar as a test instrument and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.

Don't you understand that striving for a clean distortion free sound
isnt right with a lot of guitar amps? A perfect waveform doesn't give
the sound a player might want. It`s the distortion that gives them their
characteristic sound. Setting up the bias for example - the technically
correct bias isnt necessarily the right bias (if you get my drift) They
aren't hifi amps, they are designed to colour the sound the way a
guitarist likes.

Ron

Besides, testing with a guitar is the fun part.

1 hour repair = 10 mins to replace bad capacitor + 50 mins testing
with your favorite guitar...

Mr. Land wrote:
On Mar 18, 11:28 am, "Ron(UK)" wrote:
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?
Ron
Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking
How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.
Do you have a typical stage microphone to test PA amps?
Ron
Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.
I have quite enough clutter here without a guitar as a test instrument and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.
Don't you understand that striving for a clean distortion free sound
isnt right with a lot of guitar amps? A perfect waveform doesn't give
the sound a player might want. It`s the distortion that gives them their
characteristic sound. Setting up the bias for example - the technically
correct bias isnt necessarily the right bias (if you get my drift) They
aren't hifi amps, they are designed to colour the sound the way a
guitarist likes.

Ron

Besides, testing with a guitar is the fun part.

1 hour repair = 10 mins to replace bad capacitor + 50 mins testing
with your favorite guitar...


And she`s buyyiying a staiairway to hev ennnnnn

Ron(UK) wrote in message
...
jakdedert wrote:
N Cook wrote:
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm
but
overheated colour bands look like 11 ohm ?

The polished stainless steel control panel has the legends only silk
screen
printed on. No more durable than the white markings on valves/tubes.
On/Off
and standby legends already worn off.
What is the recognised way of ameliorating this, remove pots etc,
clean off
panel with very weak solvent and spray varnish over ?

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





There is a repository of guitar amp schematics on the web, including
most of the vintage Fender models, including their many revisions.
Google would probably pull it up, or I might have bookmarked it. I'll
check....


This is a good site for diags

http://blueguitar.org/schems.htm

Ron(UK)

Schema for this one , or near enough , was on that site, ac voltages agree
reasonably well throughout from input to output. I assume that with the test
4mV in and gain controls at 50 percent they mean using a dummy load or
serious ear defenders required.

After all that it looks as though it is the 8 ohm / 4 ohm (auto) diverter
switch in the unused Switchcraft 1/4 inch external speaker socket. It looks
like a silicone rubber loop around the tip contact is the way around that,
after cleaning. The internal speaker tip contact could do with one also.
Its only 5 years old

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

What happens if in process of owner stowing away or pulling out the cables ,
foot switch etc from that convenient stowage box next the speaker, he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p transformer, it is
grounded via the built in switch contact in the socket like an input
socket..

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

N Cook wrote:
What happens if in process of owner stowing away or pulling out the cables ,
foot switch etc from that convenient stowage box next the speaker, he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p transformer, it is
grounded via the built in switch contact in the socket like an input
socket..

In that case very little will happen, the switched socket shorts out the
output. However if the socket or speaker cable were open circuit then
there`s a good chance that the output tranny, valves or valve bases
would flash over.

On Mar 18, 4:33*pm, "Ron(UK)" wrote:
Mr. Land wrote:
On Mar 18, 11:28 am, "Ron(UK)" wrote:
N Cook wrote:
Ron(UK) wrote in message
. ..
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?
Ron
Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking
How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.
Do you have a typical stage microphone to test PA amps?
Ron
Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.
I have quite enough clutter here without a guitar as a test instrument and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.
Don't you understand that striving for a clean distortion free sound
isnt right with a lot of guitar amps? A perfect waveform doesn't give
the sound a player might want. It`s the distortion that gives them their
characteristic sound. Setting up the bias for example - the technically
correct bias isnt necessarily the right bias (if you get my drift) They
aren't hifi amps, they are designed to colour the sound the way a
guitarist likes.

Ron

Besides, testing with a guitar is the fun part.

1 hour repair = 10 mins to replace bad capacitor + 50 mins testing
with your favorite guitar...

And she`s buyyiying a staiairway to hev ennnnnn

We were forbidden to (try to) play that where I worked...

Mr. Land wrote:
On Mar 18, 4:33 pm, "Ron(UK)" wrote:
Mr. Land wrote:
On Mar 18, 11:28 am, "Ron(UK)" wrote:
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
Ron(UK) wrote in message
...
N Cook wrote:
The gain on both channels is too high in my reckoning.
Feeding only a 1mV RMS, 400 Hz, (600 ohm source) into a guitar amp
input
I
would not expect the output to be on the uncomfortable side of
listening
to
continuous sine at vol setting 3.
0.12V ac rms over 8 ohm speaker at "3" and 0.39V ac at "6".
At "3" setting 0.19V ac (measured as if it was sine RMS) on both
splitter
driver outputs
No distortion at that sort of low level input.
What and where in the preamp to look for somethiong amiss?
Have you tried it with a guitar?
Ron
Nope, I've always intended picking up a magnetic pick up from somewhere
but
never have, let alone a guitar.
But all other amps i've fed this sig gen into then around 100mV is the
norm
for just speaker output signal monitoring purposes, rather than dummy
load
checking
How do you repair guitar amps if you dont have a guitar? It`s not all to
do with specs and test gear you know, some guitar amplifiers have huge
amount of gain and are intended to produce a quite specific colour of
distortion.
Do you have a typical stage microphone to test PA amps?
Ron
Balanced or unbalanced Sure mics for those tests and sig gen for guitar
amps.
I repair amps, not disrepair them. So a good sine in and a good sine out,
with any luck a clean channel, or at least minimisable distortion.
If its a "repair" job concerning the wrong sort of distortion then I turn
them away.
I find muso terminology for such stuff impenetrable as do they, not
understanding temminoloy as cross-modulation, clipping etc.
I have quite enough clutter here without a guitar as a test instrument and I
still would not understand what they're interpretation was for the wrong
distortion/s anyway.
Don't you understand that striving for a clean distortion free sound
isnt right with a lot of guitar amps? A perfect waveform doesn't give
the sound a player might want. It`s the distortion that gives them their
characteristic sound. Setting up the bias for example - the technically
correct bias isnt necessarily the right bias (if you get my drift) They
aren't hifi amps, they are designed to colour the sound the way a
guitarist likes.
Ron
Besides, testing with a guitar is the fun part.
1 hour repair = 10 mins to replace bad capacitor + 50 mins testing
with your favorite guitar...
And she`s buyyiying a staiairway to hev ennnnnn

We were forbidden to (try to) play that where I worked...


Have you ever wondered what Jimmy Paige plays when he`s trying out a
guitar in a music shop?

I have visions of some 12 y/o kid snatching the guitar off him saying...
"No No it goes like THIS!"


Ron(UK)

Ron(UK) wrote in message
...
N Cook wrote:
What happens if in process of owner stowing away or pulling out the
cables ,
foot switch etc from that convenient stowage box next the speaker, he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p transformer,
it is
grounded via the built in switch contact in the socket like an input
socket..

In that case very little will happen, the switched socket shorts out the
output. However if the socket or speaker cable were open circuit then
there`s a good chance that the output tranny, valves or valve bases
would flash over.

How much does the matching transformer heat up with a direct short ?

What happens to the output valves, droppers etc I can't believe they are
self limiting ?

Years ago someone asked me to repair a Selmer valve amp that he'd shorted
the speaker lead on and the primary side, high impdeance side, of the o/p
transformer went o/c , but I never asked how long it was "running" like
that.


--
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
...
Ron(UK) wrote in message
...
N Cook wrote:
What happens if in process of owner stowing away or pulling out the
cables ,
foot switch etc from that convenient stowage box next the speaker, he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p transformer,
it is
grounded via the built in switch contact in the socket like an input
socket..

In that case very little will happen, the switched socket shorts out the
output. However if the socket or speaker cable were open circuit then
there`s a good chance that the output tranny, valves or valve bases
would flash over.

How much does the matching transformer heat up with a direct short ?

What happens to the output valves, droppers etc I can't believe they are
self limiting ?

Years ago someone asked me to repair a Selmer valve amp that he'd shorted
the speaker lead on and the primary side, high impdeance side, of the o/p
transformer went o/c , but I never asked how long it was "running" like
that.



If I were you I would take some time and do some research about how valve
amplifiers work, you clearly have little idea. A short circuit is way safer
than an open circuit. An open circuit feeds up to twice the HT voltage back
into the output valves and can destroy them and lots of other stuff in an
instant. A short circuit will take much longer to do any real damage,
generally longer than a guitarist will spend playing his guitar with no
sound coming out of his speakers.

Get yourself a book on valve amplifiers and read it, you will be amazed
about how different the discipline is to solid state. It's never too late to
learn.


Gareth.

"msg" wrote in message
...
Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back into the output
valves...

For us 'across the pond', what does 'HT' stand for?

Michael


High Tension - the High voltage supply rail, usually 300 to 500 plus volts.
Shove double that back into an output circuit and it is likely to go bang.


Gareth.

msg wrote in message
...
Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back
into the output valves...

For us 'across the pond', what does 'HT' stand for?

Michael


This is where my
UK / USA Tool Terminology Translator
http://www.divdev.fsnet.co.uk/tool_terms.htm
comes in

Or it would if Google had not decided to de-index it a couple of months back

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

Gareth Magennis wrote in message
...

"N Cook" wrote in message
...
Ron(UK) wrote in message
...
N Cook wrote:
What happens if in process of owner stowing away or pulling out the
cables ,
foot switch etc from that convenient stowage box next the speaker, he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p
transformer,
it is
grounded via the built in switch contact in the socket like an input
socket..

In that case very little will happen, the switched socket shorts out
the
output. However if the socket or speaker cable were open circuit then
there`s a good chance that the output tranny, valves or valve bases
would flash over.

How much does the matching transformer heat up with a direct short ?

What happens to the output valves, droppers etc I can't believe they are
self limiting ?

Years ago someone asked me to repair a Selmer valve amp that he'd
shorted
the speaker lead on and the primary side, high impdeance side, of the
o/p
transformer went o/c , but I never asked how long it was "running" like
that.



If I were you I would take some time and do some research about how valve
amplifiers work, you clearly have little idea. A short circuit is way
safer
than an open circuit. An open circuit feeds up to twice the HT voltage
back
into the output valves and can destroy them and lots of other stuff in an
instant. A short circuit will take much longer to do any real damage,
generally longer than a guitarist will spend playing his guitar with no
sound coming out of his speakers.

Get yourself a book on valve amplifiers and read it, you will be amazed
about how different the discipline is to solid state. It's never too late
to
learn.


Gareth.




Left to me I would have been perfectly happy leaving valve stuff back in the
fifties and earlier.
But these musicians and HiFi nuts will keep buying the stuff and then expect
people to repair mid 20th century technology that is unbelievably still
being made in the 21st C.


--
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
...
Value of 1W, R67 near the footswitch socket, measures about 1200 ohm but
overheated colour bands look like 11 ohm ?

The polished stainless steel control panel has the legends only silk
screen
printed on. No more durable than the white markings on valves/tubes.
On/Off
and standby legends already worn off.
What is the recognised way of ameliorating this, remove pots etc, clean
off
panel with very weak solvent and spray varnish over ?

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







I tried lacquering a test spot but it did not like the metal, would wear
away as quickly as the Lettraset type silkscreen printing. I did add a few
white Lettraset legends totally worn off
A sheet of celluloid over the lettering and under the bush nuts and taped
,hidden, along the sides looks quite presentable.


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

Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back
into the output valves...

For us 'across the pond', what does 'HT' stand for?

Michael

Left to me I would have been perfectly happy leaving valve stuff back in
the
fifties and earlier.
But these musicians and HiFi nuts will keep buying the stuff and then
expect
people to repair mid 20th century technology that is unbelievably still
being made in the 21st C.





I'm very glad some of it's still being made, otherwise it would be much
harder to find tubes for vintage equipment. I'd never worked on a piece of
tube equipment before until a couple years ago when I got an old radio but I
was pleasantly surprised how easy it was to deal with, I don't see how it's
unreasonable to expect people to repair it, I was able to adapt so any real
tech ought to be able to as well. I'm under no illusion of tubes sounding
"better" but I do think they're cool, like much other old technology.

msg wrote:

Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back
into the output valves...

For us 'across the pond', what does 'HT' stand for?

Michael


B+


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"N Cook" wrote in message
...
Gareth Magennis wrote in message
...

"N Cook" wrote in message
...
Ron(UK) wrote in message
...
N Cook wrote:
What happens if in process of owner stowing away or pulling out the
cables ,
foot switch etc from that convenient stowage box next the speaker,
he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p
transformer,
it is
grounded via the built in switch contact in the socket like an input
socket..

In that case very little will happen, the switched socket shorts out
the
output. However if the socket or speaker cable were open circuit then
there`s a good chance that the output tranny, valves or valve bases
would flash over.

How much does the matching transformer heat up with a direct short ?

What happens to the output valves, droppers etc I can't believe they
are
self limiting ?

Years ago someone asked me to repair a Selmer valve amp that he'd
shorted
the speaker lead on and the primary side, high impdeance side, of the
o/p
transformer went o/c , but I never asked how long it was "running" like
that.



If I were you I would take some time and do some research about how valve
amplifiers work, you clearly have little idea. A short circuit is way
safer
than an open circuit. An open circuit feeds up to twice the HT voltage
back
into the output valves and can destroy them and lots of other stuff in an
instant. A short circuit will take much longer to do any real damage,
generally longer than a guitarist will spend playing his guitar with no
sound coming out of his speakers.

Get yourself a book on valve amplifiers and read it, you will be amazed
about how different the discipline is to solid state. It's never too late
to
learn.


Gareth.




Left to me I would have been perfectly happy leaving valve stuff back in
the
fifties and earlier.
But these musicians and HiFi nuts will keep buying the stuff and then
expect
people to repair mid 20th century technology that is unbelievably still
being made in the 21st C.


I don't think you realise quite what you're saying there. We had a debate
about this on here some time back, and it was questioned as to how relevant
valve technology was, when these amplifiers were just old relics of a bygone
age, and basically not much sold / made any more. A number of people were
surprised at the statistics supplied by the store that I carry out this
service work for. The owner said that approximately 70% of his new gear
stock, was valve, and that every 'serious' guitar player aspired to owning a
valve amp. As far as James' contention that there is not a "better" sound
from a valve amp, I think that very much depends on what you're putting
through it. There is little if anything better sounding than a Fender Strat
played through an (original) Twin Reverb. The smooth response, gentle
clipping, and inherent 2nd harmonic distortion, all contribute to a sound
that is particularly suited to a guitar.

I think that this needs to be understood, along with a fairly deep
understanding of general valve theory, in order to be successful at carrying
out this sort of repair. If Mr Cook really dislikes the gear to the extent
that he appears to, then I would venture to suggest that this is not a very
good platform to be working from, and perhaps he should stick to the
semiconductor amps, that he seems happier with.

As far as Gareth saying that valve guitar amps are "designed to distort a
lot", I'm not sure that I quite agree with that. I would suggest that they
are designed to be fundamentally clean, but with the *ability* to distort a
lot, in the right way, in the right hands. In many instances, a musician
will require a clean sound from his guitar or other instrument, or even
vocals, and it would be a poor design indeed, that couldn't give him that
....

Also, it is perfectly possible to carry out repairs to this equipment,
without being able to play a guitar. I've been doing it for the better part
of 40 years. All that is needed is a good understanding of how the equipment
*should* perform under test conditions, and this is largely down to
experience. If a 'muso' feels that there is something wrong sound-wise with
his amplifier, it's usually possible to strip the nuts and bolts meaning out
of his muso-speak, and find a technical reason for the problem. Your 'scope
and experience will soon tell you when you've resolved that problem.

Arfa

Michael A. Terrell wrote in message
...

msg wrote:

Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back
into the output valves...

For us 'across the pond', what does 'HT' stand for?

Michael


B+


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What is the US term for EHT (Extra High Tension) , say more than 1KV ?

B++ ?

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

Arfa Daily wrote in message
...

"N Cook" wrote in message
...
Gareth Magennis wrote in message
...

"N Cook" wrote in message
...
Ron(UK) wrote in message
...
N Cook wrote:


I don't think you realise quite what you're saying there. We had a debate
about this on here some time back, and it was questioned as to how
relevant
valve technology was, when these amplifiers were just old relics of a
bygone
age, and basically not much sold / made any more. A number of people were
surprised at the statistics supplied by the store that I carry out this
service work for. The owner said that approximately 70% of his new gear
stock, was valve, and that every 'serious' guitar player aspired to owning
a
valve amp. As far as James' contention that there is not a "better" sound
from a valve amp, I think that very much depends on what you're putting
through it. There is little if anything better sounding than a Fender
Strat
played through an (original) Twin Reverb. The smooth response, gentle
clipping, and inherent 2nd harmonic distortion, all contribute to a sound
that is particularly suited to a guitar.


Sentences like
"There is little if anything better sounding than a Fender Strat
played through an (original) Twin Reverb"
are absolutely useles on an electronics repair forum.

Now if you could point to a site that has electrograms and spectrum alalysis
plots, and sound files, of differnet guitars/pickuups/amps/cabs being played
in different modes along with , (consensus if possible) muso "technical"
language in their terms, their audio description, then it would indeed be a
very useful addition.
With an extra file giving sound files of common fault conditions simulated,
ie fault induced clipping rather than musical effect, pops , hiss, crackle,
hum, buzz, half complementary pair signal, etc that techies could point
owners to, for such noises appearing intermittently and rarely on the work
bench.


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

N Cook wrote:

Michael A. Terrell wrote in message
...

msg wrote:

Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back
into the output valves...

For us 'across the pond', what does 'HT' stand for?

Michael


B+


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What is the US term for EHT (Extra High Tension) , say more than 1KV ?

B++ ?


B+ is the plate supply, no matter how high the voltage. It is from
the early days of radio:

The 'A battery' powered the filaments.

The 'B battery' powered the plates.

The 'C battery' provided the grid bias.


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Michael A. Terrell wrote in message
...

N Cook wrote:

Michael A. Terrell wrote in message
...

msg wrote:

Gareth Magennis wrote:

snip

An open circuit feeds up to twice the HT voltage back
into the output valves...

For us 'across the pond', what does 'HT' stand for?

Michael


B+


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What is the US term for EHT (Extra High Tension) , say more than 1KV ?

B++ ?


B+ is the plate supply, no matter how high the voltage. It is from
the early days of radio:

The 'A battery' powered the filaments.

The 'B battery' powered the plates.

The 'C battery' provided the grid bias.


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What do you call the seriously high PDA (post deflection acceleration
voltage) in an oscilloscope or TV, surely something other than B+ ?


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

N Cook wrote:
Gareth Magennis wrote in message
...
"N Cook" wrote in message
...
Ron(UK) wrote in message
...
N Cook wrote:
What happens if in process of owner stowing away or pulling out the
cables ,
foot switch etc from that convenient stowage box next the speaker, he
unknowingly pulls out the internal speaker plug.
Turns the amp on and tries turning up the wick to get some output.
With no speaker plug inserted the 8 ohm line from the o/p
transformer,
it is
grounded via the built in switch contact in the socket like an input
socket..
In that case very little will happen, the switched socket shorts out
the
output. However if the socket or speaker cable were open circuit then
there`s a good chance that the output tranny, valves or valve bases
would flash over.
How much does the matching transformer heat up with a direct short ?

What happens to the output valves, droppers etc I can't believe they are
self limiting ?

Years ago someone asked me to repair a Selmer valve amp that he'd
shorted
the speaker lead on and the primary side, high impdeance side, of the
o/p
transformer went o/c , but I never asked how long it was "running" like
that.


If I were you I would take some time and do some research about how valve
amplifiers work, you clearly have little idea. A short circuit is way
safer
than an open circuit. An open circuit feeds up to twice the HT voltage
back
into the output valves and can destroy them and lots of other stuff in an
instant. A short circuit will take much longer to do any real damage,
generally longer than a guitarist will spend playing his guitar with no
sound coming out of his speakers.

Get yourself a book on valve amplifiers and read it, you will be amazed
about how different the discipline is to solid state. It's never too late
to
learn.


Gareth.




Left to me I would have been perfectly happy leaving valve stuff back in the
fifties and earlier.
But these musicians and HiFi nuts will keep buying the stuff and then expect
people to repair mid 20th century technology that is unbelievably still
being made in the 21st C.



I don't understand, in general valve gear is far far easier to repair
than modern surface mount solid state stuff, Once you get a grip on the
basic theory, it`s all so logical.

Ron(UK)

N Cook wrote:

Now if you could point to a site that has electrograms and spectrum alalysis
plots, and sound files, of differnet guitars/pickuups/amps/cabs being played
in different modes along with , (consensus if possible) muso "technical"
language in their terms, their audio description, then it would indeed be a
very useful addition.
With an extra file giving sound files of common fault conditions simulated,
ie fault induced clipping rather than musical effect, pops , hiss, crackle,
hum, buzz, half complementary pair signal, etc that techies could point
owners to, for such noises appearing intermittently and rarely on the work
bench.

It doesn`t really work like that with valve music gear. anyway, most
of the stock faults on the more common amps are well known among the
guys (and gals) who repair the stuff for a living, and well documented
on the web.


Ron(UK)

"N Cook" wrote in message
...
Arfa Daily wrote in message
...

"N Cook" wrote in message
...
Gareth Magennis wrote in message
...

"N Cook" wrote in message
...
Ron(UK) wrote in message
...
N Cook wrote:


I don't think you realise quite what you're saying there. We had a debate
about this on here some time back, and it was questioned as to how
relevant
valve technology was, when these amplifiers were just old relics of a
bygone
age, and basically not much sold / made any more. A number of people were
surprised at the statistics supplied by the store that I carry out this
service work for. The owner said that approximately 70% of his new gear
stock, was valve, and that every 'serious' guitar player aspired to
owning
a
valve amp. As far as James' contention that there is not a "better" sound
from a valve amp, I think that very much depends on what you're putting
through it. There is little if anything better sounding than a Fender
Strat
played through an (original) Twin Reverb. The smooth response, gentle
clipping, and inherent 2nd harmonic distortion, all contribute to a sound
that is particularly suited to a guitar.


Sentences like
"There is little if anything better sounding than a Fender Strat
played through an (original) Twin Reverb"
are absolutely useles on an electronics repair forum.

Well, not if you work on this stuff a lot, and have at least a basic
understanding of the 'musicality' of particular guitar / amplifier
combinations. If you hear a cheapo 'starter' guitar, played through a fully
solid state amplifier more suited to vocals, or a keyboard, then listen to
say a Fender / Fender combination, you'd know what I mean. I suspect that
most on here who do this work seriously, know exactly what I'm saying.


Now if you could point to a site that has electrograms and spectrum
alalysis
plots, and sound files, of differnet guitars/pickuups/amps/cabs being
played
in different modes along with , (consensus if possible) muso "technical"
language in their terms, their audio description, then it would indeed be
a
very useful addition.
With an extra file giving sound files of common fault conditions
simulated,
ie fault induced clipping rather than musical effect, pops , hiss,
crackle,
hum, buzz, half complementary pair signal, etc that techies could point
owners to, for such noises appearing intermittently and rarely on the work
bench.

Despite what some on here would sometimes have you believe, occasionally, it
*is* just subjective. I would actually think that it would be pretty
difficult to analyse the difference to the point of being able to
demonstrate it, technically. By suggesting that this was 'not your thing', I
intended no offence to your abilities. I know many engineers that are very
good in many fields, but not in the repair of valve amps. I am sure that
there are others out there who, unlike me, are properly musical, that have a
far better ear for problems than I do.

As an example, a few months back, I had a valve band amp in that just
'didn't sound right'. The owner said that it was quiet, and sounded 'thin'.
It wasn't actually all that quiet, but maybe a little compared to what he
was used to. 'Thin' was a good description of the sound. You couldn't really
say that it lacked in bass, or any other register really. It just sounded,
well thin ! With a sine wave and a 'scope and a power load and meter, there
was barely anything amiss with the output waveform or power level. The one
thing that did show on the 'scope, was a slight asymmetry to the wave, but
it was slight, and could have easily been missed. The problem turned out to
be the screen feed resistor on one of the output valves (just a 2 rather
than a 4 valve lineup). It was completely open, so there was no screen
voltage on that valve at all, which would have meant that it was barely
working, so you might have expected to have seen a much more distorted
waveform at the output, as you would have with a semiconductor amp.

When the resistor was replaced, and that valve's contribution to the output
stage was restored, there was little difference in either the overall sine
output power, or the waveshape, but the sound was now much better than
before. It now sounded 'right'. Now I know that doesn't explain the
mechanism of why or just how it sounded 'thin' before, and 'round' after,
but as an engineer doing a lot of this stuff, I knew that it was now
repaired, and the owner agreed. He made a point of calling the shop, and
telling them how 'good' (there we go again ...!) it sounded compared to how
it had for some time. So I make no excuse for using phrases on here like
that I used with the Fender ...

Arfa

N Cook wrote:

What is the US term for EHT (Extra High Tension) , say more than 1KV ?

B++ ?


B+ is the plate supply, no matter how high the voltage. It is from
the early days of radio:

The 'A battery' powered the filaments.

The 'B battery' powered the plates.

The 'C battery' provided the grid bias.

What do you call the seriously high PDA (post deflection acceleration
voltage) in an oscilloscope or TV, surely something other than B+ ?


B+ is a class of supply, B is high voltage, and + indicates it is
negative ground, so all readings will be positive. Individual supplies
may be labeled: 'Second anode', 'High voltage', 'Focus'. It depends on
the item. You see transmitters with thousands of volts, at high
current. Before the metering it is still B+, and after may be called
the plate supply, or plate voltage.

You need to download the scan of Radiotron Designers Handbook (4th
edition)

http://www.pmillett.com/Books/intro_RDH4.pdf is one source. This is a
25 MB download, but has more about Vacuum tubes than any other book you
will likely find in a single book than any other.

http://www.pmillett.com/ has other books on tubes, as well.


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Michael A. Terrell wrote in message
...

N Cook wrote:

What is the US term for EHT (Extra High Tension) , say more than 1KV
?

B++ ?


B+ is the plate supply, no matter how high the voltage. It is from
the early days of radio:

The 'A battery' powered the filaments.

The 'B battery' powered the plates.

The 'C battery' provided the grid bias.

What do you call the seriously high PDA (post deflection acceleration
voltage) in an oscilloscope or TV, surely something other than B+ ?


B+ is a class of supply, B is high voltage, and + indicates it is
negative ground, so all readings will be positive. Individual supplies
may be labeled: 'Second anode', 'High voltage', 'Focus'. It depends on
the item. You see transmitters with thousands of volts, at high
current. Before the metering it is still B+, and after may be called
the plate supply, or plate voltage.

You need to download the scan of Radiotron Designers Handbook (4th
edition)

http://www.pmillett.com/Books/intro_RDH4.pdf is one source. This is a
25 MB download, but has more about Vacuum tubes than any other book you
will likely find in a single book than any other.

http://www.pmillett.com/ has other books on tubes, as well.


--
aioe.org is home to cowards and terrorists

Add this line to your news proxy nfilter.dat file
* drop Path:*aioe.org!not-for-mail to drop all aioe.org traffic.

http://improve-usenet.org/index.html

So you don't have a generic equivalent for the term EHT which could be any
voltage, from anywhere, for any purpose, anywhere between say 1 and 50 KV ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
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