Peavey classic 30 tube amp no sound.

[guysilvermt]

I just cleaned the tube sockets and the pots on this amp. It had been popping and crackling like crazy, but this fixed the problem and it was sounding the best it has since I bought it. I was stoked then after playing for 10 minutes of bliss and all sound was lost, then smoke! I unplugged it removed the tubes and pulled out the board. To get at everything you have to unfold it like a taco! Its not something I want to do if I don't have to because I noticed a blown capacitor that would be reasonably easy to replace without doing any of that. If you look at the attached schematic its C39 my question is would this capacitor being blown make the amp not produce any sound at all or should I suspect other problems? I don't want to have to unfold the board but I don't want to wait for parts and not fix the problem either. I don't see any other visible issues

 

[daschnoz]

Did you check for continuity in F2? If the cap blew and shorted while doing so, it is possible that the fuse is blown. I know, it's a "well duh" kind of question, but it's often these simple things that are overlooked.

If the cap puked a mess all over the inside the amp, you could have a small piece of foil shorting something out. You may need to open the thing up anyway.

 

[Brian Roth]

I'm not a guitar amp guy but see some things to check.

Is fuse F2 blown? Check it out of circuit with an Ohmmeter. Is it the correct size...1 Amp fast blow? Reason for the last check is to make sure it hadn't been "slugged" with an over sized amperage value.

(while writing this I saw @daschnoz said the same thing..lol)

Test the diodes CR7/8/9/10, especially for short circuits.

Does C40 "look" ok? C39 and 40 are subjected to the exact same voltage, so both could have problems. Or, perhaps C39 just had a bad day....

Bri

 

[Brian Roth]

After I replied, I signed off to watch the 10:00 local news and weather, and I had two thoughts for the OP.

You DO realize that you're poking around in a very high voltage section of the amplifier. Do you know proper safety procedures?

Second....IF F2 is blown AND it was the proper rating (1 Amp fast blow) was the wire inside the glass cylinder merely broken, or had it left a "poof" of black material inside the glass cylinder?

Bri

 

[pucho812]

Carful with that amp Eugene, you don’t want to shock yourself.

 

[NoisyIndividual]

If C39 is blown as you say, you really should replace the identical C40 as well.
Then check the 4 diodes are OK and change the fuse F2 anyway.

 

[guysilvermt]

Just checked F2 and F3. They are both operational and don't appear to be tampered with. I do know that I could shock myself but my understanding is that it's not a concern on this particular amp when unplugged though I don't intend to go blindly searching around with my hands. I will check the rest of your suggestions next.

 

[guysilvermt]

And C 40 does not appear to have blown but I will replace it as suggested.

 

[guysilvermt]

Fuses are right values as well though I removed them without noting which was where assuming they were the same. I will be sure to return them to their proper posts.

 

[guysilvermt]

Dang it I was so happy with how it was sounding then I made smoke. I think it just might have been that caps time but it seems its always something going wrong with me as of late can't get a break.

 

[guysilvermt]

Im gonna check my board graveyard for a temporary cap of that value for testing purposes, Im really not into unfolding these 3 boards tacoed together and happy that blown caps is accessable, though solder joints on tube sockets are apparently notoriously common fail points on this model and to get to them is a delicate process. Im not really the delicate type

 

[guysilvermt]

Also I found the so called death cap and that peavey doesn't show any of the 120 part of the circuit where this X2 cap is a danger and should be a Y2 cap? Don't know exactly what this means besides it might kill me so I'll stay away.

 

[NoisyIndividual]

Theese are great sounding amps but the folded PCB construction is a bit of a nightmare.

Just one caveat - I think the mains transformer has a non resettable thermal fuse buried in it? Not 100% sure.
So don't be tempted to run it until you have replace both of those capacitors, rather than just snip the bad one out.

I've changed a few of these transformers, fortunately I think TAD make a replacement.

 

[guysilvermt]

Yes, most all if not all Peavey amps have these caps across the line voltage. First thing I do when one of these amps comes in is remove those two caps you took a pic of. Because these amps have a grounded plug (3 prong) those two cPs don't serve a purpose. TAKE THEM OUT! Lol

This is from another forum apparently remove these caps and replace with nothing? Not sure if I'll be doing that? Unless someone who understands this a bit more also thinks it's a good idea?

 

[guysilvermt]

Also I didn't check main fuse as I suspect dashnoz is speaking of.

 

[NoisyIndividual]

In the UK I only ever see 230v versions, maybe these caps were never fitted here.

 

[guysilvermt]

It appears that they are fitted on mine?

 

[guysilvermt]

Main fuse is good. Diodes 7 8 9 10 test good. Upon further inspection I believe C40 is blown. Didn't find any used caps of their value in the graveyard. Im ording them or maybe I should bite the bullet and do a complete change? Here is a pic of the blown caps, I think I can replace these two without in tacoing the boards but maybe I should just go all out replace all the caps and open her up for a deeper inspection? What do you guys think? 40 is on left

 

[NoisyIndividual]

It appears that they are fitted on mine?

Yours is 110v version, mine is 230v.

The left cap is definitely leaking, the right is probably the same or not far behind.
Do not turn on the amp like this.

 

[guysilvermt]

Yeah noisyindividual it appears you not only don't have the death caps but also your power supply is wired slightly differently? Not sure I want to mess with those death caps as I don't really understand their purpose if I was to remove them would I have to add any jumper wires or anything?