Traynor Custom Valve 40 no output.

[Sgt_Schu1tz]

I recently picked up this amp for very cheap untested. The seller told me that it was squealing if it got bumped but it did turn on. Due to the low price I bought it without testing because I figured I could use parts off it if it ends up being a lemon. When I had time to look it over at home there was quite a bit I noticed. I first made sure the fuse was the correct value and that it wasn't blown. Then I took the back cover off to get better access to the tubes. I noticed the speaker was unplugged, so I put my meter across it to make sure it wasn't open. It responded with a little bump of the cone, so I assumed that was fine and plugged it back in. Being a little impatient and partly not caring if it goes up in smoke, I decided to power it up and see if there was any life in it. Looked to make sure the filaments were all glowing and noticed one of two power tubes was not glowing. Tried to get some noise out of it anyway and touched the input lead while messing with the volume knobs. There was no sound, not even a hum or crackle.

So I unplugged it, took the chassis out and attempted to pull the non glowing tube. The tubes are a little recessed into the chassis, so you can't really grab at the base of the tube but have to pull from the glass (Also as a side note, the spring retainers that go over the tubes seemed to have a bit too excessive tension on them in my opinion to be pressed against the glass of the tubes.) Anyways, the moment I grabbed the tube I noticed the whole glass bottle was loose from the base. It wasn't separated from the base, but it was loose and lost its vacuum. I tried to remove the other tube as well and surprisingly (even though that heater had been glowing) the glass of that tube was loose as well. So I figured those tubes are probably not conducting anymore. Those tubes that were in it were a matched pair of mesa 6l6gc's. All that I had on hand were some 5881's. I don't know what power tubes this amp was originally intended to have (I've been having some trouble finding information on this amp). I put in the 5881's and tried to get some sound out of the amp again. Still no sound though. So I decided to open up the chassis (kind of a hassle) and check out some more stuff.

First I checked to make sure I had continuity on the primary and secondary of the output transformer and not to anywhere it shouldn't. That all seemed to check out. So then I checked to make sure the tube sockets were getting the voltages they need. I checked for high voltage (I heard this amp has some known issues with the standby circuit. Instead of a mechanical switch, it is done remotely with a little push button switch and some FET's). I was getting high voltage at the plate, but I think this particular amp has those standby issues because pin 3 seemed to have high voltage regardless of the standby switch being on or off. On startup (with the power tubes removed) the voltage would jump up to about 440v and then steadily climb over the next minute or two to about 515v. The main filter cap is only rated for 450v and it looks a little bloated. I checked for negative bias and that measured at -32v (does that sound right)?. After I checked those, I put the 5881's back in and put my meter across the resistor that is on the cathode to see if there was any signs of life. Nothing happening cathode-side. (I should mention that after the amp was unplugged I put my meter in pin 3 to see how much voltage was still on it; and when I touched the pin, the speaker bumped a little. So I dont think anything is wrong with the OT). One final note, I had a new-in-box set of 6l6eh's that I was reluctant to sacrifice on this amp. But I finally put those in because I wasn't sure about the 5881's. The result was the same though. No output and nothing happening across the resistor on the cathode.

So I'm kind of at a loss of where to go from here. I kind of have a feeling that it's something to do with the power section/standby circuit. There is a number of transistors and the like in that area that might be messing with things. I also forgot to mention the power transformer was tweaked to one side and the preamp tubes and phase inverter are all rattly, so its safe to assume this amp had a good drop or two in its life. But if anyone has some idea or suggestions, I'm all ears and would appreciate the help.

One last thing is this amp seems to be an older model. The power cable is hardwired to the amp. and in order to get into the chassis the power and output transformers come out with one half of the chassis and the circuit boards remain with the other half. It's an annoying set up to say the least. the newer ones seem to just have a lid that comes off with the all of the transformers and circuitry remaining in place.

Anyways thanks if you stuck through the end. I'm glad to answer any questions I can.

 

[Sgt_Schu1tz]

The amp in question.

 

[Sgt_Schu1tz]

Silly me, I forgot to check the screen voltage. Measuring pin 4, there is no voltage showing up. Now just have to find out why. I don't see any physical signs like hot or burnt components. I still think it has something to do with some of those switching components for the standby.

 

[Peegoo]

I have not looked at the schematic...but if the effects loop is a series (vice parallel) format, and one of the loop's internal jack switches is bad, you'll have no signal going from the preamp to the power stage.

Try this: connect the send and return jacks with an instrument cable and see if that makes the amp work. If it does, you need to clean those jacks.

 

[Sgt_Schu1tz]

Ok, so I found a pdf of the schematics. Beginning at pin 4 of the power tubes and working back I started checking resistors with the meter. R89 and R90 are supposed to be 220 ohms. R90 was fine, R89 was a little low at 190 ohms. But the resistor next in line down from those two (R93) was reading open on my meter. To double check I powered the amp up and verified that the resistor was open. I had voltage on the incoming side and nothing on the side going to the tube sockets. I don't know if i should just change those components and hope for the best or whether if there is an easy way to check for shorted components down the C40, R94, and R106 branches which all are connected at that point. Do you think that the condition of the tubes as they were is a likely suspect for making that resistor go open? That (R93) is a 5watt resistor. The two screen resistors down stream from that (R98 and R90) are both 1 watt resistors. You would think that if the short was in the tubes, then those two screen resistors would burn up before that 5watt. But if the short was down a different branch, that would explain why the screen resistors are fine. Also I don't see any signs of heating or damage on any of these components.

Here are a few photos from today. And here is the schematic.

Also that main power cap needs to be changed.

 

[dogmeat]

I have might some parts for ya....

 

[Sgt_Schu1tz]

Checking near by components I noticed some discrepancies between my board and the one drawn in the schematic. The location of some of the components is different, but more importantly so are some of the values. My attention is drawn to this capacitor (C60). On the schematic it is listed as 10U 450v, but as the photograph attached shows, my board has a capacitor rated 220n 250v. I checked to make sure it was connected the same way as the schematic. It was, and R106 (which is supposed to be 100k) was measuring at 60k.
I don't know what the voltage drop would be across R93 and R106, but I'm thinking that it would still be a bit above 250v which that cap (C60) is rated at.

Also(I don't know if this counts for anything but) I measured resistance across the cap and it was at a steady 750k ohms. Is that enough to be safe to say that it is leaking? or could it be those zener diodes that are causing that reading? I'm not sure.

Some other things I noticed (which maybe I should have noticed before) were that the main cap has been replaced before. It was a 100uf instead of 82uf and it had the goofy price tag shown in the picture. It was kind of hidden on the back behind some wires. the power transformer could use some grommets on the secondary side for the wires going through the chassis. The Transformer was canted to one side like the amp had been dropped and the wires were pushed tight against one side of the hole. I bent the transformer feet back so the transformer sits straight now. The wires aren't pressed against the edge anymore, but it still seems like there should be a grommet there. Don't know if thats how they came or not. And finally next to the power tube sockets, what I thought was some letters abbreviating something, when looked at from another angle appears to be a little surfing dude.

 

[Sgt_Schu1tz]

I have might some parts for ya....

Thanks for the offer, but I might go in the same boat as you if I cant get it going. (Just taking the transformers and any other usable parts for a new amp project.

 

[dan40]

It wasn't separated from the base, but it was loose and lost its vacuum.

I have had several older, octal base tubes that still functioned just fine even though the plastic base had come loose from the glass envelope. The plastic base is a separate piece that is glued onto the glass envelope so as long as the glass itself has not fractured, the tube could still hold it's vacuum and function normally. This issue usually occurs in older, vintage tubes in which the adhesive that holds the base onto the glass has dried up and failed. An NOS tube dealer once told me that black RTV silicone will work well to reattach the base so that's what I usually grab if this issue ever pops up.

If your tube's silver flashing has turned white inside, your tube is definitely toast and will need replacing.

 

[Sgt_Schu1tz]

Changed out the screen resistors, changed the big filter cap, and added some grommets. put in some sacrificial 5881's. Seems Like everything is alright.

The plate voltage (with the current limiter in line with the amp) settled down around +394v.
I'll check the bias when I get some new tubes for it.

I'll report back if anything problems pop up.

 

[Sgt_Schu1tz]

Quick question, the schematics for this amp say 6l6gb for the power tubes; can i just put in 6l6gc's instead? Comparing the datasheets, the only difference seems to be that the 6l6gc's can handle higher plate voltages. but other than that the resistance and stuff seems to be the same.

Would it be correct to say the only thing that changes is the 6l6gc would be less strained compared to the 6l6gb?

 

[Sgt_Schu1tz]

I'm having a little confusion with the bias circuit on this amp. The new 6l6gc's are in. But they are running really cold. I checked the plate dissipation and here is what it read.

Measuring the resistance of the primary side of the OT I got:

88.8ohms

120.3 ohms

and for VD across them:

1.82v

2.25v

Current:

1.82v/88.8ohms = 0.02049A

2.49v/120.3ohms = 0.02069A

Power:

390v * 0.02049A = 7.99w

387v * 0.02069A = 8.00w


So they are running really cold. I am unsure how the negative bias works on this amp.

Unlike the schematic there is no trim pot on the amp I own. Would I be right in thinking that changing the negative bias requires changing the value of R78?

 

[Bob Womack]

1. Back in the '70s, Traynor was know for cold biasing EL-34s. I had the same tubes in a '73 for twenty years and they were fine.
2. Back in the '70s, Traynor was also known for its standby scheme which wasn't a standby system at all, but a mute.

Keep your eyes open on the schematic to see whether those two conditions are intentional.

Bob

 

[Sgt_Schu1tz]

1. Back in the '70s, Traynor was know for cold biasing EL-34s. I had the same tubes in a '73 for twenty years and they were fine.
2. Back in the '70s, Traynor was also known for its standby scheme which wasn't a standby system at all, but a mute.

Keep your eyes open on the schematic to see whether those two conditions are intentional.

Bob

But 8 watt plate dissipation seems really low, for any 6L6, doesn't it?

 

[Bob Womack]

But 8 watt plate dissipation seems really low, for any 6L6, doesn't it?

Yup. Just didn't want you to jack it up too far.

Bob

 

[Grateful Ape]

I have one of the early ones - 2001? Sounds great (especially once I replaced the speaker) but it's had loads of problems, specifically the standby (eventually, it was bypassed) and the reverb. Good luck with the fix.

 

[andrewRneumann]

But 8 watt plate dissipation seems really low, for any 6L6, doesn't it?

That note on the schematic about 350mV would seem to indicate a target of 35mA of current per 6L6. I didn’t read the whole thread, sorry if this doesn’t help. It seems bizarre to me that an amp as complicated as this would leave out the bias trim pot. What’s going on here?

 

[Wound_Up]

I recently picked up this amp for very cheap untested. The seller told me that it was squealing if it got bumped but it did turn on. Due to the low price I bought it without testing because I figured I could use parts off it if it ends up being a lemon. When I had time to look it over at home there was quite a bit I noticed. I first made sure the fuse was the correct value and that it wasn't blown. Then I took the back cover off to get better access to the tubes. I noticed the speaker was unplugged, so I put my meter across it to make sure it wasn't open. It responded with a little bump of the cone, so I assumed that was fine and plugged it back in. Being a little impatient and partly not caring if it goes up in smoke, I decided to power it up and see if there was any life in it. Looked to make sure the filaments were all glowing and noticed one of two power tubes was not glowing. Tried to get some noise out of it anyway and touched the input lead while messing with the volume knobs. There was no sound, not even a hum or crackle.

So I unplugged it, took the chassis out and attempted to pull the non glowing tube. The tubes are a little recessed into the chassis, so you can't really grab at the base of the tube but have to pull from the glass (Also as a side note, the spring retainers that go over the tubes seemed to have a bit too excessive tension on them in my opinion to be pressed against the glass of the tubes.) Anyways, the moment I grabbed the tube I noticed the whole glass bottle was loose from the base. It wasn't separated from the base, but it was loose and lost its vacuum. I tried to remove the other tube as well and surprisingly (even though that heater had been glowing) the glass of that tube was loose as well. So I figured those tubes are probably not conducting anymore. Those tubes that were in it were a matched pair of mesa 6l6gc's. All that I had on hand were some 5881's. I don't know what power tubes this amp was originally intended to have (I've been having some trouble finding information on this amp). I put in the 5881's and tried to get some sound out of the amp again. Still no sound though. So I decided to open up the chassis (kind of a hassle) and check out some more stuff.

First I checked to make sure I had continuity on the primary and secondary of the output transformer and not to anywhere it shouldn't. That all seemed to check out. So then I checked to make sure the tube sockets were getting the voltages they need. I checked for high voltage (I heard this amp has some known issues with the standby circuit. Instead of a mechanical switch, it is done remotely with a little push button switch and some FET's). I was getting high voltage at the plate, but I think this particular amp has those standby issues because pin 3 seemed to have high voltage regardless of the standby switch being on or off. On startup (with the power tubes removed) the voltage would jump up to about 440v and then steadily climb over the next minute or two to about 515v. The main filter cap is only rated for 450v and it looks a little bloated. I checked for negative bias and that measured at -32v (does that sound right)?. After I checked those, I put the 5881's back in and put my meter across the resistor that is on the cathode to see if there was any signs of life. Nothing happening cathode-side. (I should mention that after the amp was unplugged I put my meter in pin 3 to see how much voltage was still on it; and when I touched the pin, the speaker bumped a little. So I dont think anything is wrong with the OT). One final note, I had a new-in-box set of 6l6eh's that I was reluctant to sacrifice on this amp. But I finally put those in because I wasn't sure about the 5881's. The result was the same though. No output and nothing happening across the resistor on the cathode.

So I'm kind of at a loss of where to go from here. I kind of have a feeling that it's something to do with the power section/standby circuit. There is a number of transistors and the like in that area that might be messing with things. I also forgot to mention the power transformer was tweaked to one side and the preamp tubes and phase inverter are all rattly, so its safe to assume this amp had a good drop or two in its life. But if anyone has some idea or suggestions, I'm all ears and would appreciate the help.

One last thing is this amp seems to be an older model. The power cable is hardwired to the amp. and in order to get into the chassis the power and output transformers come out with one half of the chassis and the circuit boards remain with the other half. It's an annoying set up to say the least. the newer ones seem to just have a lid that comes off with the all of the transformers and circuitry remaining in place.

Anyways thanks if you stuck through the end. I'm glad to answer any questions I can.

The speaker being unhooked doesn't sound good. If they were stupid enough to run it that way, it's pooched, isn't it?

Edit: nevermind. Seems like you're well on your way to getting it going. I can't offer any other help here so I'll step out and watch from here on out lol.

 

[Sgt_Schu1tz]

I found a schematic that looks closer to the circuit that is in the amp I'm working on. Thinking about getting a 10k bias pot and a 27k resistor and putting them in place of R78, the same that the updated schematic shows.. They would have to be mounted somewhere remotely though.

I would really like to be able to figure it out on paper and just order that value resistor. If that is possible, I don't know how one would go about doing it. (If anyone knows, I would be happy to hear.)


The other option is getting a few different resistor values or a breakout box and substituting values until the desired bias is achieved.

Also wondering if the 6l6gc's that i got in this amp will sound alright, as I don't think the power supply could handle biasing them up to what they are capable of. They would have to run cold and I have heard some people say the tone will suffer as a consequence. I will give the 6L6gc's a go, but might end up putting some 5881's in, as the schematic calls for 6L6gb's.

 

[dogmeat]

heres the manual I used for mine... looks a little different. it has a mod at the end for certain serial number amps

edit: file is too large to attach. I'll PM it to you. it that don't work we may have to go to email if you want it