Traynor YCV80 Repair Log

[7704A]

I've seen amp builds in this sub-forum, so I'm assuming this is the place for repair logs too.

Anyhow, picked up a partly busted YCV80 in trade for a DIY tubescreamer clone I made (the stewmac one, with some durability tweaks). Sounds pretty good through my EVM cab. Sounded pretty crap through the original combo cab with 70/80's in it. Made that into a frankencab and flipped it, now I just have the stuff I care about, the actual amp.

First problem: Volume is way too low. Maxed clean channel volume, master nearly all the way up to be at what I'd call "daytime noodling volume". At 80W I should be dead, or nearly so, so that ain't right. Dirt channel is better, but not by much.

Second problem: Oscillations. Guess I can put off purchasing a theremin for now. Max volume and gain on dirt, and I can't push the treble past noon without it squealing. Turn on the boost, and I can play a medley with the oscillation by tweaking the tonestack knobs.

Third problem: No reverb.

 

[7704A]

Oh, problem four: the treble pot for the clean channel is loose.

Anyhow, opened it up. Pictures to be posted later. Several issues, from what I see.

1) The heatsink for the power mosfets melted the insulation on a chassis ground wire that got too close.
2) The treble pot for the clean channel snapped it's legs off its body and pulled the anchoring tabs right out of the solder joints on the PCB.
3) The area around the treble pot looks like it has a bunch of rust dust. Presumably from the pot, which looks rusted/corroded. Said pot is also frozen.
4) On the flip side of the pre-amp board, a section of trace under the area for the treble pot is just gone. Looks like it was eaten away by corrosion? Some other parts of the trace nearby almost look like the soldermask is bubbling off them.
5) The return level PCB-mounted pot for the parallel FX loop has some spots in its travel where the wiper goes open circuit. Looks like the pot took an impact, had to bend the frame back into shape.

For (2) and (5), I've contacted Traynor about purchasing replacements, and told me they'll be sending out the two pots free of charge. Sweet.

(2) makes me wonder how signal is passing through the clean channel. Without the pot's internal connections there should be no path through the stage, so presumably I'm just hearing leakage from somewhere. Maybe this pathway is related to the oscillations?

(4) I plan to resolve by soldering a jumper wire in place of the trace, after cleaning up the area. The missing trace is part of the bias circuitry for some transistors, but it's just switching circuitry. Not sure if the transistors possibly acting up could affect stability or not. It's the trace connecting C25's cathode and Q6's collector in the schematic below.

(1) will be resolved with some heat shrink, and tying down the ground wire so it doesn't touch the heat sink again.

As far as the reverb tank, I measured the DC resistance of the input and output with my DMM, and the output is open-circuit. Replacement reverb tanks are available, but for now I'm just going to jumper reverb tank send/returns on the board with the appropriate load resistors to simulate the tank load, then remove the coupling caps tying the reverb circuit into the signal path. I've read elsewhere about oscillations in a modern Traynor that only appeared when the reverb tank was unplugged, so I'm hoping that once the circuitry has the right load things behave.

 

[311boogieman]

Sorry man.

Can't tell though if you are asking for help or you are just going to document how you fix it and you don't need any help. Otherwise, I'd start with the power tubes, then the caps and then the transformers. Good luck.

 

[Ben Waylin]

You can do some cool stuff with those.

Run the output of channel 2 into channel 1 and add a master volume.

 

[7704A]

Sorry man.

Can't tell though if you are asking for help or you are just going to document how you fix it and you don't need any help. Otherwise, I'd start with the power tubes, then the caps and then the transformers. Good luck.

It was primarily meant as documentation, though of course anything helpful people chime in with is appreciated. Definitely not above needing help. Power tubes should be good, the guy I got the amp from said he had replaced the tubes to fix the volume issue but no dice. Should still check though. I'm putting off the standard checks you mentioned though until I get the obvious damage repaired, the thinking is that I don't want to chase gremlins that only exist because of the current damage.

 

[7704A]

Run the output of channel 2 into channel 1 and add a master volume.

Yowza! I think the amp already kinda does that, electrically speaking. The first stage is shared between channels, and then the clean channel adds a stage and the gain channel adds two stages. Turning on the boost inserts the clean channel's second stage before the gain channel's second stage, so you get 4 stages total. It also removes the clean's eq though, so it gets fairly thick and hairy, not at all like the wicked marshall tone you posted a video of.

 

[311boogieman]

It was primarily meant as documentation, though of course anything helpful people chime in with is appreciated. Definitely not above needing help. Power tubes should be good, the guy I got the amp from said he had replaced the tubes to fix the volume issue but no dice. Should still check though. I'm putting off the standard checks you mentioned though until I get the obvious damage repaired, the thinking is that I don't want to chase gremlins that only exist because of the current damage.

That's cool.
Again good luck. I played one of these combos a long time ago and really liked it.
I just hate to see people get no response when they need help

 

[7704A]

Again good luck. I played one of these combos a long time ago and really liked it.

Yeah, it sounds wicked cool through my EVM cab. Still a few things I'd like to change about it, and I plan on doing an eyelet board conversion down the line, but it's pretty good as-is.

I just hate to see people get no response when they need help

Thanks for making sure that didn't happen.

 

[7704A]

Small update. I found some RCA jacks in a scrap parts box, and I'll just solder resistors onto those that match the impedances of the input and output transformers for the busted reverb tank. Then I can just plug the RCA cables from the amp into those, instead of modifying the PCB by directly soldering resistors across the reverb circuit's RCA jacks. Easier to A/B with/without the resistor loads too.

 

[7704A]

Just received the replacement pots from Traynor! Free of charge, including shipping costs, and it's out of warranty! Nice touch on their part, I definitely appreciate it. Now I gotta resist the urge to ditch everything else to work on the amp. Only five days until the weekend...

 

[7704A]

The area where the troublesome treble pot used to be. When I was the amp it had froze up and dismembered itself already, only held in place by the knob on the shaft. Also the trace that's out to lunch in the same area on the flip side of the board. Except it's not. While trying to remove the remnants as part of replacing it, found that there is actually copper still there, a lot of it, and the trace tests as continuous, which I could have sworn
I checked for already.

 

[7704A]

So far I've cleaned that area and replaced the pot, replaced the fx return pot, and disconnected the reverb RCA cables. Tests indicate that the amp works better now. Clean channel has more output than before, and I can do a full right-hand sweep on the dirty channel without immediately sending the amp into irritating feedback.

Issues that still need resolving:

Amp is still way too quiet for 80W. Clean channel full-bore is quieter than my 5W monoprice.

Still some feedback depending on how I poke/flex the pre-amp board and associated connections.

Weird mechanical-like noise when palm muting with the boost on through the dirty channel. Sounds kinda like bad fret buzz, happens only on the lower 2-3 strings. Guessing it's oscillation, but I don't know yet.

Next Steps:

Check more voltages. The power supply is outputting around 400V and 300V for the power and preamp anodes, but I have not checked at the tube sockets yet. So checking all necessary operating voltages needs to be done.

'scope the amp to find oscillation.

I suspect a bad solder joint or two. We'll see.