Peavey 5150 II killing speaker cables

[Burnam]

You may have a damaged pad(s) on the board from too much "tube rolling". This happens. Try gently rotating the tubes in a small circular motion and listen for crackles and noise. If there is none then I think you may need to clean the tube sockets again. Too much tube rolling can be a problem for board mounted sockets because the pads and traces become damaged. And even chassis mount sockets WRT introduction of oxide and grime.

Yeah I'm not sure if I damaged the pads connecting the socket to the board or not. I just finished tightening the pins inside the sockets, but same problem once I finished that. I also tried the old power tubes and the old phase inverter pre amp tube (different things from googling), but still the same problem of really low volume.

[Burnam]

Also, you mentioned cleaning the speaker jacks on the amp but didn't say if you examined the solder connections.
It's possible unplugging/plugging the speaker cable temporarily restored an intermittent solder connection on the jack.

I do not see any bad solder joints near any of the 1/4" inputs on the back of the amp.

[Enzo]

Plugging into the FX return bypasses the preamp, so it is normal the controls have no effect. But also, since the problem still exists when you go in through the FX return, it isn't my pet JFET issue.

Check what the above posts suggest. Clean the impedance select switch. Also, just set the impedance switch to a different choice, it doesn't matter if it is "wrong" impedance, this is only a test.

[Burnam]

Plugging into the FX return bypasses the preamp, so it is normal the controls have no effect. But also, since the problem still exists when you go in through the FX return, it isn't my pet JFET issue.

Check what the above posts suggest. Clean the impedance select switch. Also, just set the impedance switch to a different choice, it doesn't matter if it is "wrong" impedance, this is only a test.

So I tried the different impedance setting. First I tried 16 ohm setting on the amp selector into a 16 ohm 5150 4x12 and IT WORKED LIKE IT'S SUPPOSED TO. This is where I thought it was the impedance switch. Then I tried it 16 ohms from the amp into the 8 ohm 2x12 it worked. Then I tried the 2x12 on 8 ohms and it worked. Then I tried the 16 ohm 4x12 with amp settings at 8 ohm really quick and it worked. Then I jammed for about 15-20 minutes and it worked fine.

Now, mind you, I had the FX send/return jumped with an instrument cable and the effects loop was activated the entire time of the above. I next clicked the FX off on the pedal and I lost volume like before. I turned the FX back on with the pedal and it was the same low volume. I tried restarting the amp and low volume still.

I think it's bed time. I've been on this all day haha. Thanks for the help!

[Chuck H]

So something hinky about the switching for the FXL or, still possibly dirty or bad jacks.

[Burnam]

So something hinky about the switching for the FXL or, still possibly dirty or bad jacks.

Yeah definitely something weird with the FX loop, I'd guess. Weird that I've never had this problem until now. I have had this amp for over 15 years!

Today I am going to:

Check footswitch operation
Recheck speaker input/solders
Reheck FX loop input/solders
Reseat ribbon cable from Poweramp to main board and check for continuity
Replace V3=FXloop with old tube (5th preamp tube from input jack)

Any other ideas are welcome!

[Chuck H]

Yeah definitely something weird with the FX loop, I'd guess. Weird that I've never had this problem until now. I have had this amp for over 15 years!

Well grime and wear are distinctly subject to time, right? Check solder, pads and traces for damage on FXL jacks. If it looks ok then clean the jacks. If that doesn't do it then you may have a switching problem. Which I doubt is related to the foot switch itself.

[Enzo]

Weird that I've never had this problem until now

Everything works until it doesn't, y'know...

FX loop relay could be iffy contacts

[Burnam]

I've been playing with it again and got it to work. It's definitely the speaker input jacks. I cleaned them again and tried to slightly bend the metal contacts inside. They were hard to access without removing them from the board. I'm going to order some more online and replace them.

FX loop is fine and better than before, after cleaning. I had noticed a slight volume drop before the issues, but it is gone now. So 2 birds stoned at once.

I'll report back if I have any more problems. Thanks for being so helpful! I really appreciate it. Especially after my terrible diagnosis

[Randall]

"It's definitely the speaker input jacks."

Assume you meant speaker output jacks?

[Burnam]

"It's definitely the speaker input jacks."

Assume you meant speaker output jacks?

Yes, thanks!

[Chuck H]

I've been playing with it again and got it to work. It's definitely the speaker input jacks. I cleaned them again and tried to slightly bend the metal contacts inside. They were hard to access without removing them from the board. I'm going to order some more online and replace them.

FX loop is fine and better than before, after cleaning. I had noticed a slight volume drop before the issues, but it is gone now. So 2 birds stoned at once.

I'll report back if I have any more problems. Thanks for being so helpful! I really appreciate it. Especially after my terrible diagnosis

Strange that it would trigger when switching the effects loop. We'll be here if anything changes. And FWIW I've "fixed" a lot of amps just by cleaning all the contacts.

[Burnam]

Strange that it would trigger when switching the effects loop. We'll be here if anything changes. And FWIW I've "fixed" a lot of amps just by cleaning all the contacts.

I had the footswitch on my work bench with the amp. Maybe I hit it hard enough to jostle the amp and move the cable. Who knows. I played it for about 2 hours today and it was fine.