Peavey Delta Blues 30 (15x1)

[yggdrasil]

Hi, I have had my delta blues amp for about 5 years now, its been around with me and a great amp. I recently started having problems with her. I use it to play harmonica. I had taken a break and the amp was in my shed for a while, lent it to my brother then my band got back together and I pulled it out of retirement.
I played one practice with it and everything was working just fine. Then I did something stupid, one night I plugged in a bass guitar and played it for about 5 minutes.
The amp just stopped making noise. I figured I had blown a tube or something so I retubed her (needed to be done anyway). I am still getting nothing, not a single sound of it.
I got the main part out of the cabinet and am trouble shooting it, don't see any blown fuses or any burned traces. I have downloaded a schematic but it doesn't have any voltage marks on it. Can anyone here point me in the right direction for where to go ?
I can see the v2 tube has light on and I think v1 has some light on it. But v 4-8 (finals) don't have any and are not heating up.
I am pretty good with a meter and can follow a schematic pretty good.
Anyone out there got an idea of what I should check for first ?
Heard there was some diodes on the tubes somewhere or something ?
Thanks!!!

[trem]

You say you did not SEE a blown fuse. Did you put a meter on the fuse.?
If you disconnect the speaker from the OT, and put a ohm meter on the speaker, what kind of numbers do you get.?
Good Luck

[Enzo]

Inside there are a couple fuses side by side on the end of a circuit board - right next to where the transformer wires plug on. One of them is probably ceramic, which means you can't see into it anyway. It is probably blown. You can use a glass fuse in its place. But to be sure, pull each fuse from its clip and check it with a meter.

And of course always work with the amp unplugged from the wall, the voltages inside can KILL YOU.

[yggdrasil]

fuse isn't blown.

Hi, I saw that fuse and replaced it just to be on the safe side. Ill double check my work again tomorrow. After my first attempt at muscking the amp did fire up for a while but died after the first song in practice. I'll pull all the fuses and test em tomorrow.
Thanks.

[Enzo]

If the fuse is now good and the power tubes don't light, check a couple resistors for open. Look at the two fuses, now cross over to the next board, around the corner so to speak, and right near the fuses but on the center board are two 5 watt 3 ohm resistors. See if either is open. Or broken free.

And they are wired in series, so if one is dead, they all are. If the solder fails on any of the sockets on the heater pins, they all die.

Also, power off, unplug from wall, discharged. The three main circuit boards are joined together by a row of short bare-wire jumpers betweeen them.. get under each jumper with a small screwdriver or something and gently tug. See if any are broken free.

[yggdrasil]

None of those.

Hi Enzo, Thanks for the help.
Heres what I did.:
1) pulled the fuses and tested. all good theree.
2) Checked the ohmage on the four big white resistors and they are 2 @ 3 ohms and 2 @ 100 ohms.
3) Checked the solder on all of them and tested the traces into the next hole on the pcb. all good .
4) checked all the jumpered connectors on the three boards and they are all good, nothing loose and all the solders looks to be nice and firm.

So the board is now completely out of the chassis, anything else I should be looking for ?

[yggdrasil]

I'm trying to measure voltage coming out of the Second black output transformer. Wich wires come from it? I am assuming the Red Brown and Blue bunch. Is this ac or dc and What sort of voltage should I see?
Ive got it back in the chassis and tubes back in v1-3 are heating up but v4-8 are stone cold.

[Jazz P Bass]

What you are tring to read is the primary of the output transformer.
Blue & Brown are go to the output tube plates.
Red is the HIGH VOLTAGE B+.
So if the output tubes do not "light up", why are you testing the B+ DC voltage?
It was stated by Enzo that the output tubes are series connected.
If one of the tubes heater filaments goes open circuit, the rest of the tubes will not get any voltage.
(Think certain Christmas tree lights. One bulb goes bad & the whole string remains dark)
If you have a bad tube it is hard to troubleshoot the circuit.

[yggdrasil]

I thought he was referring to the resistors as being in series. Not the tubes. I will put my new tubes in and check what that does .

[yggdrasil]

Ok, not sure what I did. Replaced the tubes and got it to fire up by moving # 6 around in its socket (loose socket) but now I can get it to turn on even with the old tubes. Put it all back together and now I have this loud high pitched squeal that goes from low to high with all the volumes down.
anybody have any ideas?
I could also hear it when the speaker was unplugged.
Did I plug something in backwards?

[Enzo]

Yes, that transformer connector with the brown, blue, and red wires. Try reversing it.

[yggdrasil]

Well I left the amp at my office and I'll be off for the next four days. I'll have to wait until Tuesday morning to switch that over...
Hope it works.

[yggdrasil]

Ok, well you were right about that wire.
So I got in there and put the wire back.
Everything worked for about 10 minutes then all the tubes blacked out again.
After messing around I noticed that when I cocked v6 a bit sideways they would all fire up.
So I thought that I had a loose socket pin.I went in and gave em all a little tweak and still had the same problem.
After A while I managed to get the tubes to stay on by cocking the tube and letting it sit, but then after about 10 minutes I would get this wierd high pitched going to higher pitched noise and although the tubes would stay on I couldn't get any output.
Well at this point cocking the tube in there sideways was not working out so well, and I would have to manually hold it at an angle and push it up then all the tubes would come on and it would work. So I busted it all open again and took a look at that tube socket, all looked ok.
I then started testing the continuity from the pin receptacle to their next stop on the pcb.
Lo and behold one of the pins (possibly pin three) although the solder connection looked like it was ok, it was not making continuity to the next stop on the pcb. The solder was a bit light here and I so I pulled out the iron and filled it up.
Now I am looking Like im back to normal.
In the meantime I have a new set of tubes.
v1 is a sovtek 5751 v2 is a jj ecc83 v4 is a eh 12ax7 and jj el84s for the rest of the.
Thank you for all your help, the real clue was when I realized what enzo had said about the final tubes being like Christmas lights. Then I realized what was happening in there.
I now know a hell of a lot more about my amp, and I've got a pretty good feeling about fixing it myself and saving a decent chunk of change.
Thanks alot everyone.