Peavey Encore 65 Amp. No Sound?

[Sigala]

Bias adjust!

Thanks Enzo
I was stating that this is not the value chosen! It was merrily an example.

That is why I was asking about Values to use for the Trim Pot and the additional resistor to get in the ball park?
So what value of trim pot and resistor to use to accomplish the variable bias mod?

I was going to buy a bias probe to check. and then adjust. Ill be using Sovtek's 5881/6L6WGC power tubes. And not sure of what the bias current should be set?

Or should I just leave it as fixed!??

Thanks Enzo

Dennis

[Buzz Crumhunger]

I think I may have just gotten lucky...

Noob here. Happy to report I picked up one of these at a pawn shop today for $75.

It was marked for $160, and I was going to lay it away at that price if it worked as it should. None of the front controls worked at all, no sound from front jacks, but one of the employees tried plugging it into the effect loop jacks (which I actually would not have thought to do) and got guitar sound out of it. Clean and a bit weak, but I figured if it was clean there then it was worth $75 just for the box, speaker, tubes, chassis and trannys. I think they must have known this wasn't working properly and were happy to be rid of it.

Tomorrow I'll try jumping the effects loop and see how that goes. I was thinking that somewhere in v1-v3 was having some kind of issue as described earlier. I used to have a VTX, same size box with 2x the tubes (130W), SS preamp section (it was SS pre-amp, wasn't it?) and monster BW 12" spkr, and it had needed a similar repair at some point.

I foolishly gave up the working chassis and speaker (still have the box!) as I was SO tired of lugging around a 90# (yes, I put it on a scale!) amp with only a mediocre sound to it. The cleans were pretty great, actually, but back then all I wanted was distortion. Anyway, based on that amp I was assuming the pre was SS until I looked and saw the little tube cage for the pre section.

Despite all of this, I have a 1959SLP PCB headed my way; this was going to be the Frankenstein / sleeper combo of the century! Now that I see the power supply provides more than adequate fixed and B+ bias, I'm thinking that may in fact be the plan. However, thanks for the thread on the pump circuit and clipping diodes. I now hope this works all on its own, but will be sorely tempted to perform open heart surgery on this ~27yo combo.

Cheers,

Buzz Crumhunger, combo fan forever.

[Buzz Crumhunger]

So, this is kind of a drag, but the guy with the 1959SLP PCB dogged me and another bidder, so I have a case open against him. (I escalated after I noticed the other guy who bid on one had also not received his.) So, ANYway, so many people spoke so highly of this amp in stock form that I am re-visiting the amp as-is.

I pulled the chassis out and looked at the schematic again and thought about it. Last time I'd pulled the 3 12AX7s and found they'd all been replaced with 12AU7s.(Someone thought it was too loud in stock form? Knew they were getting rid of it and wanted to keep the 12AX7s for another amp?) I'd individually pulled each and tested with a known working 7025 from long ago, no dice. Didn't pull the 12AT7 that day. Today I pulled all 4 preamp tubes and replaced with known working tubes and got essentially the same result: decent sound by plugging into the pwr amp in jack, nothing at all from the front panel.

Don't recall if the reverb tank had remained unplugged in prior tests, I looked at the scheme of things and thought maybe the tank does have to be plugged in to pass signal on to power section as it seems the pre section goes right to reverb driver, aka V3A. Now I see that there is a bypass path back to V3B, so I know that it SHOULD work with the tank unplugged if V3 is working, no?

During these tests at one point I did get a LOUD buzz from the reverb (turned all knobs halfway up at some point, may not have done this before), which actually was coming from the reverb tank itself buzzing to the touch! Eek?! Did someone connect the molex backwards? I hear tell that there are transducers at one end of a reverb tank and pickups at the other, but I've not taken one apart. BTW, some prior owner had removed the tank from its bag, screwed it to a 1/4" piece of plywood, then screwed the whole thing onto the bottom of the chassis on the outside, so it sticks out and the leads look kinda sketchy. So that's kind of a downer....

However, it still has the same basic problem with tank disconnected, i.e., clean sound from pwr amp in jack, no sound from front panel. Can resistors and caps blow (or open, or short?) without any external evidence? Haven't pulled out the whole PCB yet, this may be the next step: get out the Fluke and poke it a few dozen times? With or without tubes in place? Power disconnected, most certainly.

Any troubleshooting guidance or help would be greatly appreciated, thanks.