Peavey Classic 20 Power Tubes Won't Light...

[Commander]

Excellent, thank you again for the info Enzo. I was contemplating hardwiring the boards together (insulated copper wire, + shrink wrap on posts maybe?), just didn't know if I could actually get that stock jumper wire as a replacement or not. Since only one post was cooked, I think I can fasten a small piece of wire cannibalized from a motor brush and get the post to stick and make contact with what it is supposed to. Failing that, I guess the board needs to come out; it's in pretty rought shape now. I am curious, however, why rivets were used in the first place, rather than removeable fasteners to hold in the P-tube board. IF I need to drill out those rivets to get the board out, can I not replace them with screws and washers similar to what I would use in a PC motherboard installation (can't overtighten) ? It just seems like the logical step. For now, however, I will try to fix the board that is in there and see how it works, then keep all posted as to my success or lack thereof.

Great forum BTW!

TJ

[Enzo]

Rivets are secure, they won't strip like sheet metal screws, you don;t need to get behind them with a nut, they are fast and simple to use, and these boards don;t come out very often, so the few minutes you spend drilling rivets doesn't amount to much. If you can;t drill them out in 5 minutes, put down the cell phone and use two hands. REally, it shouldn't take 2 minutes. And to install the board is simple, again, 8 pop rivets takes a couple minutes tops.


Sure, you can buy ribbon wire. Looks like 0.156" spacing to match the Molex connector pitch. But why bother. Solder a wire to the end of some component on the board if there is no connector pin left or the solder pads are damaged. Or just sweat it down to a clean area of copper trace.

Were you actualy describing trying to make a connector with something springy?

HArdwire the thing around the burnt stuff. True you won;t be able to unplug it anymore, but chances are if you need to separate the boards, you are working inside and will be soldering anyway. If that is so, touch the wire end with your iron and voila, it is disconnected.

[Commander]

Got it, much appreciated. I ended up finding the last little bit of copper left on the board that once went to the pin. Not much there, but enough to solder on some copper wire and extend the connection to the other board. Amp seems to work just fine now, let's hope it stays that way, lol.

As a mechanic, I hate rivets, just my personal thing.

Thanks again,
TJ

[zabble]

Looks like i may have the exact same issue. Just received a Classic 20 purchased on ebay and discovered it is not working...exact same symptoms as described at the start of this thread.

I'm a complete noob and not an electrical technician by any stretch...i would rather be making music.

The process for getting to the circuit board...is it is simple as undoing all the screws from the sides and top of the amp and just pulling the board out?

Would i be better just getting an amp repair person to take a look at it ?

[Commander]

Get someone reputable to look at it. That way, if it gets fugged up, you are not responsible to tow the line. Another thing to consider is that since your amp was bought used, and shipped, the shipping may have damaged the tubes. Try replacing the tubes first. If it STILL won't work, then go with the service tech option. If you are unfamiliar with circuitry in general, then I advise not buggering with anything in your amp. I only did so because the "techs" I had look at my amp were likely not worthy of putting two AA batteries together, so I had to do it myself, and having a bit of training certainly helped my cause. I hope you get it sorted out, it sounds like you may have gotten burned.

[Amp Kat]

Use a magnifying glass to see the broken jumpers. Hard to see with the naked eye. This amp is so simple that there really isn't much to go wrong in the circuit but maybe a bad Cathode cap or resistor. This is one of the only Cathode biased amps Peavey ever made and one of the simplest.

[jimmybrad]

I'm sorry, the power tube heaters don;t come on, and we are suspecting the output transformer? What possible connection could the output transformer have with the power tube heaters?

The preamp tube heaters work, so the heater fuse is OK, and the transformer works. SO the problem is getting the 6vAC to the power tubes. I might suspect socket solder, but not on both tubes. SO I am drawn to the little jumper wires that connect the pc board sections together.

I am attaching a pdf of the schematic file that includes the layout. Look on the left end where jumper wires connect the top pc board to the center board. Below V4. The first and fourth jumpers carry the heater current. I bet one is broken.

In fact, as long as it is open, go down the row of jumpers. Well, two rows actually, since there are three boards. Get under each jumper wire and gently but firmly tug on it. If any come free, they were broken - fix them.

Avoid as much as posssible flexing the boards, bending those jumpers can break them off.

I gotta thank you as well Enzo, recieved a Delta Blues that had been shipped across the country. Power tubes wouldn't light. Research led me here, and immediately upon inspection I found the first jumper to be broken just like you said. I'm no amp tech but you just saved myself and the guy I bought this from a ton of trouble. A SINCERE THANKS.

[tcarnell]

Thanks Enzo! another one fixed. I bought my Peavy classic 20 amp second hand in the UK and fly it to Spain. Plugged it in and it was dead. Found this thread and was able to repair it.

For anyone unsure, I've attached a photo of the fault my amp had.

For me the repair was some straight forward soldering, although some of those jumpers would be much trickier to solder. Under adivse of my father, I also used some Araldite epoxy glue/resin to bond the two circuit boards together, which should hopefully stiffen things up and reduce stress on the remaining jumper wires (just put 5 or so small blobs spaced out along the length of the board to join the two sides together)

[kimrody]

I am attaching a pdf of the schematic file that includes the layout. Look on the left end where jumper wires connect the top pc board to the center board. Below V4. The first and fourth jumpers carry the heater current. I bet one is broken.