Peavey Special 112, Very weak ouput signal.

[DonnieG]

Checked continuity to speaker, all lines are good, speaker checked out fine.
All fuses good, no visible signs of shorts at resistors, transistors, capacitors, etc.
Has anyone had this experience and know course of action?

Guitar plays well enough to hear, but no guts, no power.
Not an issue with the guitar, I tried pushing player signal through, same result.
Some sort of issue with the output signal.

[Jerry]

The effects loop jacks get oxidized over the years and cuts out/lowers the volume. Try plugging a cable into the fx loop jacks to see if that cures it.

[Jam]

I would look real close for bad solder joints

[DonnieG]

Thanks Jerry!

I wasn't quite sure what you meant so I tried the effects send with my player and got an even weaker output than with the main inputs but when I plugged into the effects return I got what seemed to be a normal level output with good response.
So, what do I do now. I also tried another pre amp into the power amp input in the back and got a great response with that.
How do I fix this issue. Any idea what my problem is and/or course of action to correct?

[Jazz P Bass]

The pre out jack is weak.
A stong signal into the power amp in jack "drives" the power amp just fine.
Then the issue is with the preamp.
This is going to require some test equipment.
How are you set up?

[DonnieG]

The pre out jack is weak.
A stong signal into the power amp in jack "drives" the power amp just fine.
Then the issue is with the preamp.
This is going to require some test equipment.
How are you set up?

Have multimeter, soldering tools, gen handtools, magnifiers. That's about it

[Jazz P Bass]

I just read the manual
The "effects out" jack is rated at 0.3Vrms.
Did you try the "Line Out" jack into another amp?
That is rated at 1Vrms.
You can run a jumper from the Line Out to the Line in.
Maybe those contacts are funky.
Do you have the schematic?
All that I can locate is the Special 130.
I am not sure if it is the same.

[Jerry]

Donnie, if you have a spare cable, plug one end into the fx send and the other into the power amp in jack. If that brings it back to life, then you can try some contact cleaner- Cramolin Deoxit, or replace jacks with new ones. IIRC, the fx send jack is a tip/sleeve type of jack and the power amp in jack is a switching jack.

[Jazz P Bass]

Uhm. The effects send/ return are on the front of the amp.
The pre out & power amp in are on the back.
I don't see that sending the Fx return into the power amp in will prove anything.
As stated, the FX signal is 1/3 the voltage of the pre signal.
Jumpering the pre out & power in should be the next step.
As is sending the pre out to another amp.
You have to narrow down where in the circuit it is failing.

[DonnieG]

Thanks for the help, you are all very knowledgeable.
Since I followed Jerry's suggestion, I don't know how or why , but, it did come back to life.
The whole system seems to be working fine. That's amazing. I thought it was a gonner. Noone will even look at it for less than $80.00
I took the whole thing apart and cleaned everything inside out, top to bottom, and put it all back together and all is well.
Thank you all for your helpful replies!
This is a great forum!

Donnie G.
Home Studio Music

[DonnieG]

Jerry, Thanks so much,
That did the job. The thing works great!
I don't understand it but it worked.

[Jerry]

Donnie, Glad to hear that worked for you! It's happened to a few of those amps. I forgot about the fxloop jacks on the front. Give them all a good cleaning.