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Tremolo and Bias fail on Princeton Reverb clone
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chainsa...@hotmail.com
Feb 20, 2015, 2:13:36 AM2/20/15
to
About 8 years ago I built a 6L6 Princeton Reverb using the 6A14HP schematic from Weber speakers. it has been a great amp until this summer when the tremolo stopped working. Shortly afterward I had an event where the amp started humming really loudly. There was a lot of light coming off the 6L6s, and I shut it down quickly without really inspecting what I was seeing. It was just loud and bright, to the best of my memory it was yellow or white light. Now it has been 6 months or so so I may have some creative memory of the event. I set the amp off to the side and haven't touched until today.
Today I finally got around to checking it out. My completely questionable Eico 667 tests them all as good. I built the amp with 1 ohm resistors on the cathodes and probe jacks for adjusting bias. With the tremolo knobs turned down the coldest bias I can get is about 25 Watts, 426 Volts and 61mA. I plugged in a guitar and played for a minute, and it sounded OK.
What do you think I will see when I pull the chassis? Is there a likelyhood that the tremolo fail and the bias problem are related? I used some terribly cheap pots. Could an open pot wiper on the Tremolo intensity cause such weirdness?
A little background on my experience/inexperience level. I am certainly not a proper tube amp tech, just a hobbyist with a lot of experience building electronic prototypes (of a totally not-tube amp variety) at work. I have built a few radio tube amps (with 12au6 and 50C5), two champs, two very simple 6V6 pp amps (on the level of a tweed deluxe) and this high power Princeton. ...And one pretty goofy little 12AT7 amp using a reverb transformer for an output transformer. So I am fairly clueless, but perhaps not entirely clueless.
Today I finally got around to checking it out. My completely questionable Eico 667 tests them all as good. I built the amp with 1 ohm resistors on the cathodes and probe jacks for adjusting bias. With the tremolo knobs turned down the coldest bias I can get is about 25 Watts, 426 Volts and 61mA. I plugged in a guitar and played for a minute, and it sounded OK.
What do you think I will see when I pull the chassis? Is there a likelyhood that the tremolo fail and the bias problem are related? I used some terribly cheap pots. Could an open pot wiper on the Tremolo intensity cause such weirdness?
A little background on my experience/inexperience level. I am certainly not a proper tube amp tech, just a hobbyist with a lot of experience building electronic prototypes (of a totally not-tube amp variety) at work. I have built a few radio tube amps (with 12au6 and 50C5), two champs, two very simple 6V6 pp amps (on the level of a tweed deluxe) and this high power Princeton. ...And one pretty goofy little 12AT7 amp using a reverb transformer for an output transformer. So I am fairly clueless, but perhaps not entirely clueless.
chainsa...@hotmail.com
Feb 20, 2015, 2:18:28 AM2/20/15
to
That second paragraph: the Eico is my tube tester, and all the tubes are good.
Xtrchessreal
Feb 20, 2015, 3:45:49 PM2/20/15
to
There are some helpers here.
X->out
Xtrchessreal
Feb 20, 2015, 4:04:02 PM2/20/15
to
If the trem tube was failing it may have put a higher voltage or current on the output tubes which would could make them run hot, if the circuit works the way I am understanding it. I would need to research more to know for sure.
X->out
Xtrchessreal
Feb 20, 2015, 6:33:00 PM2/20/15
to
I don't know. These are just guesses based on what I understand and the schematic.
In general I use LVs advice and keep the output tubes powered on the lower end of the tubes spec. Also I have followed his advice on burning the tubes in and then check your bias one more time.
Just trying to help
X->out
Universe
Feb 20, 2015, 7:06:33 PM2/20/15
to
On Thu, 19 Feb 2015 23:13:34 -0800 (PST), chainsa...@hotmail.com
wrote:
>About 8 years ago I built a 6L6 Princeton Reverb using the 6A14HP
>schematic from Weber speakers. it has been a great amp until this
>summer when the tremolo stopped working. Shortly afterward I had an
>event where the amp started humming really loudly. There was a lot of
>light coming off the 6L6s, and I shut it down quickly without really
>inspecting what I was seeing. It was just loud and bright, to the
>best of my memory it was yellow or white light. Now it has been 6
>months or so so I may have some creative memory of the event. I set
>the amp off to the side and haven't touched until today.
>Today I finally got around to checking it out. My completely
>questionable Eico 667 tests them all as good.
LOL! They -may- be good, but I wouldn't count on it. You probably
lost bias.
That amp would have used 6V6's. Did you adapt for 6L6's?
> I built the amp with 1
>ohm resistors on the cathodes and probe jacks for adjusting bias.
>With the tremolo knobs turned down the coldest bias I can get is about
>25 Watts, 426 Volts and 61mA. I plugged in a guitar and played for a
>minute, and it sounded OK.
>
>What do you think I will see when I pull the chassis? Is there a
>likelyhood that the tremolo fail and the bias problem are related?
Yes.
>I used some terribly cheap pots. Could an open pot wiper on the Tremolo
>intensity cause such weirdness?
That's a very good bet. You won't save money if you use a cheap pot
and the output tubes blow as a result.
Replace that pot, and this time, solder a resistor from the center
(wiper) terminal to the bias supply side (connected to the bias pot).
Try maybe about 470k or so. That will ensure that if the wiper loses
contact, there will still be a connection to the bias supply.
If it's not that, then you could check the cap that connects the trem
circuit to that same pot. If it's leaky, that could also throw off the
bias. Much less likely though.
Also check the wiring up to the bias resistors, etc.
Before you change anything, unplug the output tubes and measure the
bias voltage to see what's going on. Remember that B+ will stay hot
for a long while if the output tubes are not plugged in (they are the
major discharge path for the high v supply).
Turn the pot and see if you can get the bias to screw up again. (This
time your output tubes will be unplugged).
And replace the pot even if you can't get it to screw up.
>A little background on my experience/inexperience level. I am
>certainly not a proper tube amp tech, just a hobbyist with a lot of
>experience building electronic prototypes (of a totally not-tube amp
>variety) at work.
I'm sure you'll figure it out. Do you have a scope?
wrote:
>About 8 years ago I built a 6L6 Princeton Reverb using the 6A14HP
>schematic from Weber speakers. it has been a great amp until this
>summer when the tremolo stopped working. Shortly afterward I had an
>event where the amp started humming really loudly. There was a lot of
>light coming off the 6L6s, and I shut it down quickly without really
>inspecting what I was seeing. It was just loud and bright, to the
>best of my memory it was yellow or white light. Now it has been 6
>months or so so I may have some creative memory of the event. I set
>the amp off to the side and haven't touched until today.
>Today I finally got around to checking it out. My completely
>questionable Eico 667 tests them all as good.
lost bias.
That amp would have used 6V6's. Did you adapt for 6L6's?
> I built the amp with 1
>ohm resistors on the cathodes and probe jacks for adjusting bias.
>With the tremolo knobs turned down the coldest bias I can get is about
>25 Watts, 426 Volts and 61mA. I plugged in a guitar and played for a
>minute, and it sounded OK.
>
>What do you think I will see when I pull the chassis? Is there a
>likelyhood that the tremolo fail and the bias problem are related?
>I used some terribly cheap pots. Could an open pot wiper on the Tremolo
>intensity cause such weirdness?
and the output tubes blow as a result.
Replace that pot, and this time, solder a resistor from the center
(wiper) terminal to the bias supply side (connected to the bias pot).
Try maybe about 470k or so. That will ensure that if the wiper loses
contact, there will still be a connection to the bias supply.
If it's not that, then you could check the cap that connects the trem
circuit to that same pot. If it's leaky, that could also throw off the
bias. Much less likely though.
Also check the wiring up to the bias resistors, etc.
Before you change anything, unplug the output tubes and measure the
bias voltage to see what's going on. Remember that B+ will stay hot
for a long while if the output tubes are not plugged in (they are the
major discharge path for the high v supply).
Turn the pot and see if you can get the bias to screw up again. (This
time your output tubes will be unplugged).
And replace the pot even if you can't get it to screw up.
>A little background on my experience/inexperience level. I am
>certainly not a proper tube amp tech, just a hobbyist with a lot of
>experience building electronic prototypes (of a totally not-tube amp
>variety) at work.
Universe
Feb 20, 2015, 7:11:49 PM2/20/15
to
On Fri, 20 Feb 2015 13:04:01 -0800 (PST), Xtrchessreal
<XtrChe...@gmail.com> wrote:
>I don't use a tremolo in any of my amps but from what I just read I would at least put in a new trem tube and see what happens then.
>
>If the trem tube was failing it may have put a higher voltage or current on the output tubes which would could make them run hot, if the circuit works the way I am understanding it. I would need to research more to know for sure.
>
>X->out
Hi X,
<XtrChe...@gmail.com> wrote:
>I don't use a tremolo in any of my amps but from what I just read I would at least put in a new trem tube and see what happens then.
>
>If the trem tube was failing it may have put a higher voltage or current on the output tubes which would could make them run hot, if the circuit works the way I am understanding it. I would need to research more to know for sure.
>
>X->out
The trem circuit should be isolated via a coupling cap, so unless the
cap is leaky, any DC problems behind that cap shouldn't result in
complete loss of bias.
chainsa...@hotmail.com
Feb 20, 2015, 11:09:23 PM2/20/15
to
Replacing the trem tube resulted in no change.
I did not install the master volume option. I didn't strike me as a MV kinda amp anyway, and I was really going for clean headroom with the 6l6s.
I don't think there is much difference between the Fender Princeton Reverb and the Weber 6A14HP except different transformers to allow for the 6L6 tubes.
The pot was rotated as if the mounting nut was loose. Perhaps one lug touched the chassis bottom and cooked something in the bias circuit. I saw no arc marks, but the lug did look really close to touching chassis. The pot is super wimpy. The lugs will wiggle at the rivet point. Pulled it out, un soldered it, and checked it with an ohmmeter. I couldn't get it to fail. But I have no confidence in it. It is really lightweight and fragile looking.
I didn't check any caps.
Before reading any responses I stuffed in some old crud covered 6L6s of unknown quality. I was able to bias them from 20 to 12w with the trem intensity set to zero. The trem still didn't work, and with the intensity set to ten the current went from 28 mA to 150! I turned it back down quickly. One of the tubes got pretty blue!
I read the posts and checked the bias voltave with the 6l6s removed. With intensity set to zero, bias voltage could be adjusted between -36 and -44 volts. With the intensity set to ten the voltage went to POSITIVE 2.5 volts and did not change with bias pot position.
I have a scope, a Tek T920, nearly as wonderful as the Eico tube tester!
All this time the guitar signal is making it all the way to the speaker. The amp plays and sounds OK. It is just this scary high current on the power tubes and the tremolo does not work at all.
Nothing looks burned or arced. There seem to be no sloppy solder joints. Visually everything looks good. I guess next look at all the components in the rest of the bias/trem circuit. ...and order new pots. I saved nothing buying the cheapest pots.
I did not install the master volume option. I didn't strike me as a MV kinda amp anyway, and I was really going for clean headroom with the 6l6s.
I don't think there is much difference between the Fender Princeton Reverb and the Weber 6A14HP except different transformers to allow for the 6L6 tubes.
The pot was rotated as if the mounting nut was loose. Perhaps one lug touched the chassis bottom and cooked something in the bias circuit. I saw no arc marks, but the lug did look really close to touching chassis. The pot is super wimpy. The lugs will wiggle at the rivet point. Pulled it out, un soldered it, and checked it with an ohmmeter. I couldn't get it to fail. But I have no confidence in it. It is really lightweight and fragile looking.
I didn't check any caps.
Before reading any responses I stuffed in some old crud covered 6L6s of unknown quality. I was able to bias them from 20 to 12w with the trem intensity set to zero. The trem still didn't work, and with the intensity set to ten the current went from 28 mA to 150! I turned it back down quickly. One of the tubes got pretty blue!
I read the posts and checked the bias voltave with the 6l6s removed. With intensity set to zero, bias voltage could be adjusted between -36 and -44 volts. With the intensity set to ten the voltage went to POSITIVE 2.5 volts and did not change with bias pot position.
I have a scope, a Tek T920, nearly as wonderful as the Eico tube tester!
All this time the guitar signal is making it all the way to the speaker. The amp plays and sounds OK. It is just this scary high current on the power tubes and the tremolo does not work at all.
Nothing looks burned or arced. There seem to be no sloppy solder joints. Visually everything looks good. I guess next look at all the components in the rest of the bias/trem circuit. ...and order new pots. I saved nothing buying the cheapest pots.
chainsa...@hotmail.com
Feb 20, 2015, 11:18:57 PM2/20/15
to
I imagine it might be good to disconnect the intensity pot lug going to the trem circuit, isolate the trem from the bias circuit and see if I can get normal bias that way. Then I could start scoping around the trem circuit and see if it is oscillating like it should or if it is just clamping down to one rail.
Xtrchessreal
Feb 21, 2015, 1:08:57 AM2/21/15
to
On Friday, February 20, 2015 at 9:18:57 PM UTC-7, chainsa...@hotmail.com wrote:
> I imagine it might be good to disconnect the intensity pot lug going to the trem circuit, isolate the trem from the bias circuit and see if I can get normal bias that way. Then I could start scoping around the trem circuit and see if it is oscillating like it should or if it is just clamping down to one rail.
I like Universe's idea even if you get a new pot add a 470k resistor between the center lug and to the bias supply side. It provides a good parallel R while also protecting the grids from an open contact inside the pot.
> I imagine it might be good to disconnect the intensity pot lug going to the trem circuit, isolate the trem from the bias circuit and see if I can get normal bias that way. Then I could start scoping around the trem circuit and see if it is oscillating like it should or if it is just clamping down to one rail.
testing the oscillation circuit: you might have a bad speed pot there too but I wonder why the schem calls for C11 (C3) to be 22nF and the others are 11nF the oscillating circuits I am seeing as standard C 1,2,3 are all the same value for the pos feedback input loop. Also I read that you could use an LED instead of the cathode cap and resistor to maximize the gain on the trem tube it helps with ageing tube issues as it gives a visual blink for the trem Hz, if its not blinking then the tube is probably bad or not providing the proper gain. Kind of a cool practical mod to mount a LED next to the knob.
X->out
Universe
Feb 21, 2015, 1:28:05 AM2/21/15
to
On Fri, 20 Feb 2015 20:09:21 -0800 (PST), chainsa...@hotmail.com
wrote:
>The pot was rotated as if the mounting nut was loose. Perhaps one lug touched the chassis bottom and cooked something in the bias circuit. I saw no arc marks, but the lug did look really close to touching chassis. The pot is super wimpy. The lugs will wiggle at the rivet point. Pulled it out, un soldered it, and checked it with an ohmmeter. I couldn't get it to fail. But I have no confidence in it. It is really lightweight and fragile looking.
>
>I didn't check any caps.
>
>Before reading any responses I stuffed in some old crud covered 6L6s of unknown quality. I was able to bias them from 20 to 12w with the trem intensity set to zero. The trem still didn't work, and with the intensity set to ten the current went from 28 mA to 150!
> I turned it back down quickly. One of the tubes got pretty blue!
>I read the posts and checked the bias voltave with the 6l6s removed. With intensity set to zero, bias voltage could be adjusted between -36 and -44 volts. With the intensity set to ten the voltage went to POSITIVE 2.5 volts and did not change with bias pot position.
Was that an abrupt change to +2.5, or was it gradual as the trem pot
was rotated? If it was abrupt, I would expect a cracked element in
the pot, but you indicated that the pot was OK. Also, when you tested
the pot, did you measure resistance from both outer terminals to the
wiper, or were you just measuring from one of the outside terminals?
Just for fun, turn the pot full clockwise (with the amp turned -off-)
and measure resistance between pairs of terminals. You don't need to
unsolder anything.
The other possibility is still that the coupling cap from the trem
oscillator is leaky. In that case, you would most likely see a gradual
shift as the pot was rotated.
You should try soldering in the high value resistor, as I recommended
before. Value is not critical. Something in the range of 330k upward
would do. The bias supply connects to one of the end terminals of the
trem pot. Solder the resistor between that terminal and the center
terminal. If the bias gradually goes more positive as you turn up the
trem pot, then the coupling cap is probably shorted. If the bias
stays in range after the resistor is added, then it's probably the
pot.
When you replace the pot, put the resistor in the same place. It's
always good policy to make sure that if a pot fails, the bias will
stay low.
I presume that you've checked the wiring and solder connections.
>I have a scope, a Tek T920, nearly as wonderful as the Eico tube tester!
It's always good to get an idea of what's going on AC-wise. DC
measurements can be misleading if there's a significant AC component.
Also put the scope on the plate of the trem oscillator tube to see
what's going on there. Use DC coupling. Turn the trem speed up and
down.
>All this time the guitar signal is making it all the way to the speaker. The amp plays and sounds OK. It is just this scary high current on the power tubes and the tremolo does not work at all.
Well, I wouldn't get carried away playing the amp until you find out
what's going on.
>Nothing looks burned or arced. There seem to be no sloppy solder joints. Visually everything looks good. I guess next look at all the components in the rest of the bias/trem circuit. ...and order new pots. I saved nothing buying the cheapest pots.
You learn from that. If this was a regular opto trem circuit, the pot
wouldn't be so crucial. Many people love bias-modulated trems, but
this would not be the first time that circuit caused serious problems.
Order an extra 0.1uf high voltage mylar (polyester) iso cap too, if
you don't have those in stock. Good quality, and overrate the voltage
if possible. You don't want an old decrepit cap in that spot. And
order resistors in the 470k range if you don't have them.
BTW, lost bias would red-plate the tube. Blue would either be normal
electron impact with the glass envelope, or possibly a leak..
wrote:
>The pot was rotated as if the mounting nut was loose. Perhaps one lug touched the chassis bottom and cooked something in the bias circuit. I saw no arc marks, but the lug did look really close to touching chassis. The pot is super wimpy. The lugs will wiggle at the rivet point. Pulled it out, un soldered it, and checked it with an ohmmeter. I couldn't get it to fail. But I have no confidence in it. It is really lightweight and fragile looking.
>
>I didn't check any caps.
>
>Before reading any responses I stuffed in some old crud covered 6L6s of unknown quality. I was able to bias them from 20 to 12w with the trem intensity set to zero. The trem still didn't work, and with the intensity set to ten the current went from 28 mA to 150!
> I turned it back down quickly. One of the tubes got pretty blue!
>I read the posts and checked the bias voltave with the 6l6s removed. With intensity set to zero, bias voltage could be adjusted between -36 and -44 volts. With the intensity set to ten the voltage went to POSITIVE 2.5 volts and did not change with bias pot position.
was rotated? If it was abrupt, I would expect a cracked element in
the pot, but you indicated that the pot was OK. Also, when you tested
the pot, did you measure resistance from both outer terminals to the
wiper, or were you just measuring from one of the outside terminals?
Just for fun, turn the pot full clockwise (with the amp turned -off-)
and measure resistance between pairs of terminals. You don't need to
unsolder anything.
The other possibility is still that the coupling cap from the trem
oscillator is leaky. In that case, you would most likely see a gradual
shift as the pot was rotated.
You should try soldering in the high value resistor, as I recommended
before. Value is not critical. Something in the range of 330k upward
would do. The bias supply connects to one of the end terminals of the
trem pot. Solder the resistor between that terminal and the center
terminal. If the bias gradually goes more positive as you turn up the
trem pot, then the coupling cap is probably shorted. If the bias
stays in range after the resistor is added, then it's probably the
pot.
When you replace the pot, put the resistor in the same place. It's
always good policy to make sure that if a pot fails, the bias will
stay low.
I presume that you've checked the wiring and solder connections.
>I have a scope, a Tek T920, nearly as wonderful as the Eico tube tester!
measurements can be misleading if there's a significant AC component.
Also put the scope on the plate of the trem oscillator tube to see
what's going on there. Use DC coupling. Turn the trem speed up and
down.
>All this time the guitar signal is making it all the way to the speaker. The amp plays and sounds OK. It is just this scary high current on the power tubes and the tremolo does not work at all.
what's going on.
>Nothing looks burned or arced. There seem to be no sloppy solder joints. Visually everything looks good. I guess next look at all the components in the rest of the bias/trem circuit. ...and order new pots. I saved nothing buying the cheapest pots.
wouldn't be so crucial. Many people love bias-modulated trems, but
this would not be the first time that circuit caused serious problems.
Order an extra 0.1uf high voltage mylar (polyester) iso cap too, if
you don't have those in stock. Good quality, and overrate the voltage
if possible. You don't want an old decrepit cap in that spot. And
order resistors in the 470k range if you don't have them.
BTW, lost bias would red-plate the tube. Blue would either be normal
electron impact with the glass envelope, or possibly a leak..
Universe
Feb 21, 2015, 1:49:39 AM2/21/15
to
On Fri, 20 Feb 2015 22:08:54 -0800 (PST), Xtrchessreal
<XtrChe...@gmail.com> wrote:
> I wonder why the schem calls for C11 (C3) to be 22nF and the others
> are 11nF the oscillating circuits I am seeing as standard C 1,2,3 are
> all the same value for the pos feedback input loop.
The 0.022 is fine, X. The only thing that matters is the cumulative
<XtrChe...@gmail.com> wrote:
> I wonder why the schem calls for C11 (C3) to be 22nF and the others
> are 11nF the oscillating circuits I am seeing as standard C 1,2,3 are
> all the same value for the pos feedback input loop.
180 degree shift thru the three caps. Fender uses 0.022, 0.01, 0.01
in most of their tube trem circuits.
jh
Feb 21, 2015, 8:56:54 AM2/21/15
to
Try to disconnect it (open) and look whether the odd behaviour of the
intensity pot goes away...
regards
Jochen
chainsa...@hotmail.com
Jul 8, 2015, 12:55:10 AM7/8/15
to
After 5 months I post again! Just in case sometime someone else is searching non-functional tremolo and inability to bias a Princeton Reverb (or a Weber 6A14).
Bad 6L6 tubes and a bad tremolo speed pot.
I separated the trem circuit from the bias by disconnecting the trem circuit side lug of the intensity pot. Bias was more stable, but still way too hot. Pulling the 6L6s and the bias voltage was adjustable from -30 to -50 volts or so (I forget the actual values but it was something in this ball park. I replaced the old RCA 6L6s with some new JJ 6L6s. The bias now works fine and is adjustable over a wide range of acceptable idle current. No red plates, no super bright yellow weirdness, just normal heater glow. The RCAs were given to me by a co-worker that was cleaning out junk his brother had left behind. I knew they were not new old stock. I should have realized that they were probably not still installed in one of the brothers amps for a good reason! And I trusted the old Eico 667 when they tested good. Or maybe they were good and the trem fail sent the bias whacky and damaged the RCAs. I dunno, chicken... Egg... Complex series of events obscuring exactly which is cause and which is effect?
I hooked the trem circuit back to the intensity knob. Bias was ok at intensity = 0, but increasing intensity did not bring a tremolo effect, and idle current would whip up and down in an unnaturally wide range.
I replaced the intensity pot. No change.
I replaced the speed pot. Now the trem works, bias works, and with intensity rolled up bias "wiggles" as it should but does not swing to extremes. Every thing is working now as it should. All the pots have been replaced, and I will never again buy $1.80 pots again. The CTS replacement pots were around $3.50 and I can see they are better made. Even the mounting nut is thicker.
Bad 6L6 tubes and a bad tremolo speed pot.
I separated the trem circuit from the bias by disconnecting the trem circuit side lug of the intensity pot. Bias was more stable, but still way too hot. Pulling the 6L6s and the bias voltage was adjustable from -30 to -50 volts or so (I forget the actual values but it was something in this ball park. I replaced the old RCA 6L6s with some new JJ 6L6s. The bias now works fine and is adjustable over a wide range of acceptable idle current. No red plates, no super bright yellow weirdness, just normal heater glow. The RCAs were given to me by a co-worker that was cleaning out junk his brother had left behind. I knew they were not new old stock. I should have realized that they were probably not still installed in one of the brothers amps for a good reason! And I trusted the old Eico 667 when they tested good. Or maybe they were good and the trem fail sent the bias whacky and damaged the RCAs. I dunno, chicken... Egg... Complex series of events obscuring exactly which is cause and which is effect?
I hooked the trem circuit back to the intensity knob. Bias was ok at intensity = 0, but increasing intensity did not bring a tremolo effect, and idle current would whip up and down in an unnaturally wide range.
I replaced the intensity pot. No change.
I replaced the speed pot. Now the trem works, bias works, and with intensity rolled up bias "wiggles" as it should but does not swing to extremes. Every thing is working now as it should. All the pots have been replaced, and I will never again buy $1.80 pots again. The CTS replacement pots were around $3.50 and I can see they are better made. Even the mounting nut is thicker.
Lord Valve
Jul 8, 2015, 8:23:37 AM7/8/15
to
good testers for quick screening, but the vast majority
of them were built from kits, and have wiring errors or
other weirdness. I've rebuilt several that were bought
from various sources, sold cheaply because they "didn't
work right." Name your price.
Lord Valve
NBS Electronics
Denver, CO
303-778-1156
jh
Jul 8, 2015, 5:54:37 PM7/8/15
to
regards
Jochen
chainsa...@hotmail.com
Jul 14, 2015, 12:33:14 AM7/14/15
to
LV,
If I ever do want to sell it I will give you a call. For right now I need to face up to the fact that I have done zero maintenance on this thing in the 10 or 15 years I have had it. I see I have my next project in front of me.
JH,
Yes I had to update once I had it worked out. It always bugs me a little when I google something only to find forum threads that raise a question, but never resolve it, as if the original poster just lost interest, or didn't feel the need to share the solution.
If I ever do want to sell it I will give you a call. For right now I need to face up to the fact that I have done zero maintenance on this thing in the 10 or 15 years I have had it. I see I have my next project in front of me.
JH,
Yes I had to update once I had it worked out. It always bugs me a little when I google something only to find forum threads that raise a question, but never resolve it, as if the original poster just lost interest, or didn't feel the need to share the solution.
Lord Valve
Jul 14, 2015, 9:35:23 AM7/14/15
to
On Monday, July 13, 2015 at 10:33:14 PM UTC-6, chainsa...@hotmail.com wrote:
> LV,
> If I ever do want to sell it I will give you a call. For right now I need to face up to the fact that I have done zero maintenance on this thing in the 10 or 15 years I have had it. I see I have my next project in front of me.
Here's what you should do -
> LV,
> If I ever do want to sell it I will give you a call. For right now I need to face up to the fact that I have done zero maintenance on this thing in the 10 or 15 years I have had it. I see I have my next project in front of me.
First up, eyeball *every* solder joint in the unit using
a headworn binocular magnifier or a big fat magnifying
glass. Strong illumination is the key here. (Remember -
no matter how well you can see, you can see better with
magnification and strong light.) This is a critical
step; as I mentioned before, the vast majority of these
old EICO testers were built from kits, and it's very
likely that you will find bad joints and even unsoldered
connections. Reflow any joint that's suspicious-looking.
Use a powerful iron if you have one; 60W will be OK, but
100W would be better. Low-powered irons take too long
to heat the joint, allowing heat to migrate to where
you don't want it - wire insulation, tube socket plastic,
switch wafers, etc. Add solder to any joint you reflow,
and make sure it's the good stuff - 63/37 or 60/40 tin-
lead, by Ersin or Kester.
Treat all the switch contacts with DeOxIt (red) 100% formula.
Don't spray anything onto those switches. You have 14 multi-position
lever switches and a rotary for the tube/transistor testing selector.
This is what you want for the switch contacts; you can use the brush
applicator it comes with if you don't have a hypodermic to apply it
with: http://store.caig.com/s.nl/it.A/id.1701/.f?sc=2&category=188
This is the same sauce, but more of it and with a needle applicator:
http://store.caig.com/s.nl/it.A/id.1703/.f?sc=2&category=188
Just a tiny drop on each contact will be plenty, as a little of
this particular sauce goes a long way. This is also the stuff you
want to put into the socket contacts. Easy does it here, too.
Pots can be sprayed with 5% DeOxIt red formula if they act glitchy,
otherwise, leave 'em alone. For the pots, use this:
http://store.caig.com/s.nl/it.A/id.1602/.f?sc=2&category=188
The quickest shot you can manage will be plenty.
You may have to replace the 8-pin octal and the 9-pin
miniature sockets if they're too reamed out. If you do,
get some Socket-Savers and install them.
https://www.tubedepot.com/products/9-pin-socket-saver
http://www.ebay.com/itm/like/390564386756?lpid=82&chn=ps
Tighten up the hardware (easy on the meter-mounting nuts)
and you should be good to go. You might want to replace
the line cord while you're at it - the original ones
were wimpy, and had no ground.
Lord Valve
Expert (neener neener)
chainsa...@hotmail.com
Jul 17, 2015, 2:09:47 AM7/17/15
to
Lord Valve,
Thanks for the advice and the links. I do appreciate you taking the time to write that up!
I do have a decent Weller solder station and most of a one pound spool of Kester 60/40 I bought way back before RoHS. Oh yeah, and an OptiVisor, cause I just ain't got the eyes of a 22-year-old no more. As That's good advise about soldering iron power too. As a kid in the 70s I destroyed a bunch of those Radio Shack P-Box kits by trying to solder with a 15 watt Radio Shack iron. By the time the joint was hot enough to melt solder, the heat had transferred down the component lead and melted the red plastic perforated box! I eventually learned to not bother soldering and instead just twist the leads. Only then did I ever have any luck with those kits! I wish they still had dumb kits that kids could buy with lawn-mowin' money. I think my son could learn a lot from melting plastic and burning his fingers.
Say LV, do you still do the emailed catalogs? I either have fallen off your spamlist or you haven't done one in a long time. If you still do it, how can I get back on the list?
Thanks for the advice and the links. I do appreciate you taking the time to write that up!
I do have a decent Weller solder station and most of a one pound spool of Kester 60/40 I bought way back before RoHS. Oh yeah, and an OptiVisor, cause I just ain't got the eyes of a 22-year-old no more. As That's good advise about soldering iron power too. As a kid in the 70s I destroyed a bunch of those Radio Shack P-Box kits by trying to solder with a 15 watt Radio Shack iron. By the time the joint was hot enough to melt solder, the heat had transferred down the component lead and melted the red plastic perforated box! I eventually learned to not bother soldering and instead just twist the leads. Only then did I ever have any luck with those kits! I wish they still had dumb kits that kids could buy with lawn-mowin' money. I think my son could learn a lot from melting plastic and burning his fingers.
Say LV, do you still do the emailed catalogs? I either have fallen off your spamlist or you haven't done one in a long time. If you still do it, how can I get back on the list?
Lord Valve
Jul 17, 2015, 7:51:59 AM7/17/15
to
for the yutes of America. Most of 'em are under $20, and the
instructions are great. (I have two pink noise generators I built
from Velleman kits - one of 'em's been helping me sleep for over
20 years, built into an old Peavey practice amp.) Here's a joint
that sells 'em, as well as "experimenter" parts and kits from
other sources:
http://www.kitsusa.net/phpstore/html/Velleman-Kits-174-1.html
Jameco electronics is also a cool place for stuff like this,
and they publish "build articles" from their staff and
customers. Also a source of Velleman kits, and when they
publish a "build" article they almost always provide parts
kits to go with it. I buy some of the parts I use on my
bench from them, too...they are a huge outfit:
http://www.jameco.com/1/3/velleman-kits
Also cool, Ramsey Electronics:
http://www.ramseyelectronics.com/Hobby-Kits/b/6290126011?gclid=CPagopGE4sYCFckYHwodjdYHbw
Heathkit is still with us:
https://www.heathkit.com/heathkit-faq.html
The SpamList is dormant at this point - it grew to nearly
six thousand addresses, and maintaining it became a chore
I just didn't want to do. Nowadays, I'm building a lot
of custom amps, and the repair biz in Denver is off the
charts...what with the legalized weed here, the music
scene is really heating up and that means tons of fried
gear for dudes like me to fix. A few years ago I chucked
all of my "authorized warranty center" biz out the window
and decided to concentrate on vacuum tube gear only. I
sell a shitload of tubes and tube-related parts to the
locals, and I still do a fair amount of mailorder biz
when I have time. Unfortunately, my lightning-fast
shipping time is mostly over with - I simply have too
much to do, so it sometimes takes me a week (or more)
to get orders out now. If my assistant (a brilliant young
guitarist and an enthusiastic bench tech I am mentoring)
ever gets back from his Great Los Angeles Pussy and Fame
Hunt, some of the pressure will be off and I may be able
to devote more time to Internet biz - but no more e-mailed
catalogs, I just don't have time to run the list any more.
If you need something, shoot me an e-mail or better yet,
use the phone. I can tell you what I have in stock and
also tell you about what's new and wonderful in the tube
world. For instance, JJ now makes a 5881. Absolutely
killer for Super Reverbs. (Here's where some specbook-
pounder is going to pop off and tell you they'll fry
in a Super Reverb.) Anyway, give me a shout...
Lord Valve
NBS Electronics
303-778-1156
richardni...@gmail.com
Jul 17, 2015, 11:39:22 AM7/17/15
to
Lord Valve
Jul 17, 2015, 11:57:02 AM7/17/15
to
You live on the dole, couldn't play Twinkle Twinkle Little
Star on a one-stringed ukulele if Bonamassa showed you how.
And you have no idea how to run a small business, let alone
a testbench. Not only that, you live in a country that is
nothing more than the USA's hat.
Fuck you.
richardni...@gmail.com
Jul 18, 2015, 12:52:05 PM7/18/15
to
Lord Valve
Jul 18, 2015, 3:46:27 PM7/18/15
to
Lord Valve, ThD
Electron Whisperer
richardni...@gmail.com
Jul 18, 2015, 10:43:16 PM7/18/15
to
Lord Valve
Jul 18, 2015, 10:47:35 PM7/18/15
to
I'm too far away. If you knew anything about the
logistics of an A-level touring company, you'd...
well, shit...you don't know your ass from a hole in
the ground, do ya.
And that's the way you'll remain: clueless.
Fuck you, mooseturd.
Claude V. Lucas
Jul 19, 2015, 8:15:03 AM7/19/15
to
In article <a51ae28b-f01c-4df3...@googlegroups.com>,
This one hasn't been dry since Ike was President...
chainsa...@hotmail.com
Jul 21, 2015, 1:33:06 AM7/21/15
to
Lord Valve,
Thanks again for the advice and links! It is good to hear your business is keeping you plenty busy.
I might have to try new manufacture 5881s at my next tube change. I have read that true 5881s haven't been made in a long time and that most ones made today can handle higher plate voltages. This amp puts 408 V on the plates. Are the JJs ok for that?
Thanks again for the advice and links! It is good to hear your business is keeping you plenty busy.
I might have to try new manufacture 5881s at my next tube change. I have read that true 5881s haven't been made in a long time and that most ones made today can handle higher plate voltages. This amp puts 408 V on the plates. Are the JJs ok for that?
Lord Valve
Jul 21, 2015, 6:28:02 AM7/21/15
to
LV
joth...@gmail.com
Aug 10, 2015, 8:16:44 PM8/10/15
to
Lord Valve
Aug 10, 2015, 9:01:05 PM8/10/15
to
screens are connected, the screens cannot develop any significant
positive potential with respect to the plates, which is the main
mode for screen failure in guitar amps which have no dedicated
screen supply. Therefore, I don't think you're going to see any
*voltage*-related failures. You'll be pulling a shitload of plate
current, though, and those are 23-watt rated tubes, unlike the
30-W 6L6s you removed. (And the 35-watt variations like the
7581A, 7027A, etc.) I'd keep my fingers crossed if I were you.
Lord Valve, ThD
Expert (fuck you)
joth...@gmail.com
Aug 10, 2015, 11:33:15 PM8/10/15
to
We've strayed off the thread topic, but I was reading with interest about the Princeton trem/bias issue, as I had the same experience in my silverface PR, which is very much my everyday workshop jam/demo/test workshop amp.
What are the best choices in the world of 6V6s these days?
Lord Valve
Aug 10, 2015, 11:47:03 PM8/10/15
to
On Monday, August 10, 2015 at 9:33:15 PM UTC-6, joth...@gmail.com wrote:
> On Monday, 10 August 2015 21:01:05 UTC-4, Lord Valve wrote:
> > On Monday, August 10, 2015 at 6:16:44 PM UTC-6, joth...@gmail.com wrote:
> > > On Tuesday, 21 July 2015 06:28:02 UTC-4, Lord Valve wrote:
> > > > On Monday, July 20, 2015 at 11:33:06 PM UTC-6, chainsa...@hotmail.com wrote:
> > > > > Lord Valve,
> > > > >
> > > > > Thanks again for the advice and links! It is good to hear your business is keeping you plenty busy.
> > > > >
> > > > > I might have to try new manufacture 5881s at my next tube change. I have read that true 5881s haven't been made in a long time and that most ones made today can handle higher plate voltages. This amp puts 408 V on the plates. Are the JJs ok for that?
> > > >
> > > > I'm running a pair at 440V in a Super Reverb. Kickass!
> > > >
> > > > LV
> > >
> > > I just put these in a Bassman 135 and Twin Reverb 135w @500v, replacing the JJ 6L6gc, will see how things go.
> >
> > Those are both ultralinear output stages. Because of the way the
> > screens are connected, the screens cannot develop any significant
> > positive potential with respect to the plates, which is the main
> > mode for screen failure in guitar amps which have no dedicated
> > screen supply. Therefore, I don't think you're going to see any
> > *voltage*-related failures. You'll be pulling a shitload of plate
> > current, though, and those are 23-watt rated tubes, unlike the
> > 30-W 6L6s you removed. (And the 35-watt variations like the
> > 7581A, 7027A, etc.) I'd keep my fingers crossed if I were you.
> >
> > Lord Valve, ThD
> > Expert (fuck you)
>
> Well in both of these amps, I had previously modded the bias circuit and added in a pot to have a level adjustment, in addition to the presence of the stock bias matching control. I think I'd set the JJ 6L6GC bias to draw 35mA per tube thru the 1ohm cathode resistors I'd put in. This time I have the 5881 set to 30mA per tube. Just about 15w static.
Does the output waveform show any crossover notch?
> On Monday, 10 August 2015 21:01:05 UTC-4, Lord Valve wrote:
> > On Monday, August 10, 2015 at 6:16:44 PM UTC-6, joth...@gmail.com wrote:
> > > On Tuesday, 21 July 2015 06:28:02 UTC-4, Lord Valve wrote:
> > > > On Monday, July 20, 2015 at 11:33:06 PM UTC-6, chainsa...@hotmail.com wrote:
> > > > > Lord Valve,
> > > > >
> > > > > Thanks again for the advice and links! It is good to hear your business is keeping you plenty busy.
> > > > >
> > > > > I might have to try new manufacture 5881s at my next tube change. I have read that true 5881s haven't been made in a long time and that most ones made today can handle higher plate voltages. This amp puts 408 V on the plates. Are the JJs ok for that?
> > > >
> > > > I'm running a pair at 440V in a Super Reverb. Kickass!
> > > >
> > > > LV
> > >
> > > I just put these in a Bassman 135 and Twin Reverb 135w @500v, replacing the JJ 6L6gc, will see how things go.
> >
> > Those are both ultralinear output stages. Because of the way the
> > screens are connected, the screens cannot develop any significant
> > positive potential with respect to the plates, which is the main
> > mode for screen failure in guitar amps which have no dedicated
> > screen supply. Therefore, I don't think you're going to see any
> > *voltage*-related failures. You'll be pulling a shitload of plate
> > current, though, and those are 23-watt rated tubes, unlike the
> > 30-W 6L6s you removed. (And the 35-watt variations like the
> > 7581A, 7027A, etc.) I'd keep my fingers crossed if I were you.
> >
> > Lord Valve, ThD
> > Expert (fuck you)
>
> Well in both of these amps, I had previously modded the bias circuit and added in a pot to have a level adjustment, in addition to the presence of the stock bias matching control. I think I'd set the JJ 6L6GC bias to draw 35mA per tube thru the 1ohm cathode resistors I'd put in. This time I have the 5881 set to 30mA per tube. Just about 15w static.
>
> We've strayed off the thread topic, but I was reading with interest about the Princeton trem/bias issue, as I had the same experience in my silverface PR, which is very much my everyday workshop jam/demo/test workshop amp.
> What are the best choices in the world of 6V6s these days?
The JJ is the most bulletproof 6V6 I've ever seen.
> We've strayed off the thread topic, but I was reading with interest about the Princeton trem/bias issue, as I had the same experience in my silverface PR, which is very much my everyday workshop jam/demo/test workshop amp.
> What are the best choices in the world of 6V6s these days?
It doesn't sound like a "classic" 6V6, but it's
really good in low-powered open-back amps - Princeton
Reverb, Deluxe Reverb, Champ, etc. Nice meaty low
end. But if you want the classic "American" 6V6 tone,
the Tung-Sol wins hands down. The Russians got that one
right. ;-)
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