Peavey C-30

[C Moore]

You guys with experience.....how do you Work/Test these amps.?
The tri-fold boards are real hard to get at...they are slid under the lip of the chassis, so I cannot really get a probe on them.
I pulled the boards out of the chassis, only to realize I cannot get power to them after they are free.
That is my question, how do you get power (and ground) to the boards once they are out.
All of the PT and OT leads are stuck in the chassis with the conncectors on them.
Thank You

[Deric]

What are the symptoms?

[C Moore]

Hissing/Bacon Frying.
It is on both channels, and all the Volume/Gain pots...it increases with the pots.
Just on chance, I cleaned all jacks and tube sockets.

[Stevem]

Process of elimination takes place first.
Have you swapped in known good preamp tubes yet, as it could be that simple of a fix?
If not the bacon fring issue 95 % of the time is noisy load resistors in a preamp tubes plate circuit ( pin 1 or 6) so the first thing to do is to pull out the first preamp tube that is on the oppsite side of the amp from the output tubes to see if that clears the issue, if that fails continue yanking preamp tubes out until the issue stops!
If yanking a tube clears the issue than plan on replacing all of the plate load resistors , the cathode resistors and the 47k ohm resistor off of the input jack.
These Amps are also known for having the power supply filters going bad in 10 years or less, so while you have this pain in the ass amp apart to work on it plan on replacing all of the electrolytic caps in the amp, even the cathode bypass caps in the preamp stages.
In regards to all of the big power supply filters if any of them show signs of bulging on there positive side then this could be the sourse of the issue also.

All of these resistors should be upped to 1/2 watt types if any but the 47k resistor are 1/4 watt types.
The main thing is to confirm is that this frying noise is not from a push on connector point having a bad connection and starting to burn up, so once you open up the amp take a long good look at those and into the output tube sockets and there connection points to the circuit board if that's the way the sockets are mounted, in fact this goes for all tube socket to board solder on points, rings seen around these socket connection points would be a cause of this issue also.

[labb]

If all else fails, box her up and send her back to the good old boys in Mississippi. Pretty good bunch to deal with. They still support the Classic series. Probably cost you about $100 plus shipping. Give them a call. They will talk with you.

[C Moore]

Two things I forgot to mention:
1. Sticker on amp says it was made in 10-21-2012
2. I have swapped in good tubes.

The C30 has it heaters wired in series, so it is hard (impossible.?) to pull tubes and isolate a problem.
I have checked every connection I can think of, all look and seem good.
I WILL put a magnifying glass on the tube sockets and see what I can.
Plate resistors is the first thing that I thought of. I THINK these are 1/2 Watt resistors, but they are only 3 years old, Although, I remember a few years back when Fender had A LOT of their plate resistors fail in the HRDlx seines of amps. It sure could not hurt to replace those. Will give that a shot.
Thank You
so...anybody have a trick to power up these boards.?

[dorrisant]

I built a jig for them... C-30s, Delta Blues, etc.. I drill small holes in the blank portions of the PCB and use screws to hold it to the jig. Then everything is there for testing. I usually change those solid-wire jumpers to stranded wire. This doesn't really take that long and makes the board set much more easy to deal with.

You can see where I mount the stock TX on the right. I don't connect the OT. With all of the tubes in place it is pretty simple (kinda) to start tracing and testing.

Tony

[dorrisant]

I also use the trace mask on the C-30 schematic. The DB is not much different, it just has the tremolo shoehorned in there. I cropped the PCB layout on the second page. You can use different colors of highlighter marker to indicate the different sections... Ch1, Ch 2, B+ supplies, Bias supply etc.

It seems like a lot of work, but if you ever have to do it again, you will be glad you have it..

Tony

[C Moore]

That jig is a nice idea.?
But.....how do you handle the PT leads and the grounds(s).?
Thank You

[dorrisant]

I usually just tack solder the PT primary leads to the cord whip... Wrap them with a clean cloth to isolate the primary connections. Clip lead the ground to a ground plane on the PCB, usually a component leg that is tied to schematic ground. Use the factory Molex connections from the PT to attach the B+ and filament supplies.

Tony

[dorrisant]

Also... If you leave the original solid-wire jumpers in place, do yourself a favor: Use a guitar pick to pluck each one... If it has a nice little tone (ping) to it then it is good. A dull thud indicates the need to reflow one or both of its connections. This saves tearing it back apart to find the broken connection.

Tony

[Stevem]

Another thing to note about these amps ( and many other cheap side amps) is how the circuit board traces like to peal off so easy!
In light of this what I would do if your need to replace any resistors is to simple snap them off, leave the old leads in place and install the new ones on the bottom of the board providing that there are no wires running by that would preclude you from doing so!