Peavey KB100 no sound, hum volume with reverb knob

[troyadams]

I have a Peavey KB100 that produces no sound in either of the 3 inputs. However, a hum can be heard as I turn the reverb knob up. The hum gets louder as I turn the reverb knob up.
I can also hear a small static snap as I go to plug in an instrument into any of the three inputs.
I am technically capable of making the repairs, however I need help with troubleshooting.

[Jazz P Bass]

Have you tried running a signal level patch cord from the Pre Amp Out jack to the Power Amp In jack?
If that wakes it up then you have a dirty or bad Power Amp In jack.

If not that, try sending a signal directly in to the Power Amp In jack.
That will bypass the entire preamp.
Alternatively, run the Pre Amp Out jack to another amp.

[troyadams]

Have you tried running a signal level patch cord from the Pre Amp Out jack to the Power Amp In jack?
If that wakes it up then you have a dirty or bad Power Amp In jack.

If not that, try sending a signal directly in to the Power Amp In jack.
That will bypass the entire preamp.
Alternatively, run the Pre Amp Out jack to another amp.

If I never use the pre amp out and pwr amp in jacks, then what difference would it make if they are dirty? I only plug in to the 3 inputs (which do not work except for static and hum from the reverb).
Thanks.

[The Dude]

The return jack is a switching jack. The switch connects preamp to power amp when nothing is plugged into the jack. If it's contacts are dirty or corroded, it won't switch, effectively leaving the preamp disconnected from the power amp. Here's an entire thread on the matter.

https://music-electronics-forum.com/...ad.php?t=48339

[Leo_Gnardo]

I post this so often, oughta have it on "speed dial." Hear ye, hear ye, read ALL about it, here:

The Dreaded Switching Jack Problem

https://music-electronics-forum.com/...ad.php?t=28549

-----------------------

The Dude: you beat me to it. By 2 minutes. Imma gonna hafta eat my Wheaties!

[Enzo]

Your signal runs THROUGH those jacks whether you use them or not.

[Leo_Gnardo]

Your signal runs THROUGH those jacks whether you use them or not.

I was gonna say, but I'm trying to be polite today. Don't worry it won't last long!

[troyadams]

Ok, I patched the pre amp and power amp and I get sound in all inputs but it doesn't get very loud. I removed the patch and it makes no difference. The volume on each of the 3 inputs seems to work but none get very loud.

[The Dude]

What are you plugging into the inputs? They are line level. A guitar won't likely be very loud.

[Jazz P Bass]

"If not that, try sending a signal directly in to the Power Amp In jack.
That will bypass the entire preamp.

Alternatively, run the Pre Amp Out jack to another amp."

You need to isolate the problem.
Preamp Or Power Amp.

Keep in mind it could be both.

[troyadams]

I have an Alesis Recital Pro keyboard. It is connected via the left line out mono jack into the number one (2 or 3) input on the kb100 amp. I cannot seem to get any stage quality volume out of the amp like I used to years ago. It had been unused for many years. I do get some volume, and the maximum I can get is with the input knob pulled out and cranked up to 10, and all the equalization cranked up to 15. At this setting, it is loud but it sounds terrible. And I get no compression like it used to.

[Enzo]

First things first. Have you tried the keyboard into a different amp? And have you tried a different keyboard or even a guitar into this amp? So far it is still possible the problem lies outside the amp until we verify the problem.

Then if the amp is indeed at fault, plug the instrument into the FX return jack, now how does it sound? yes, I know the controls will have no effect that way.

[troyadams]

The KB100 seems to be getting better the more I mess with it. Is that logical?
There's still some crackling in the input knobs and the overall volume is almost as loud as it used to be. Still no compression light.
I have connected the keyboard to a PA and I've also connected a banjo with a passive pickup to the KB100.

[52 Bill]

The KB100 seems to be getting better the more I mess with it. Is that logical?

Yes, it seems to me that your amp is basically in need of a 10,000 mile tune up. Get yourself a can of DeoxIt contact cleaner and use it to clean all of the pots and all of the jacks (yes, even the ones that you don't use). You should also clean all of the Molex connectors that run from the different pc boards and transformers, etc. If the amp has been regularly gigged with and has been moved around a lot, you should also check the pc board for loose or broken solder connections.

Everything oxidizes with time. The different metal contact points in the amp are slowly being covered with a film of dirt, corrosion, dust that will change the way that they conduct electricity. In the case of the loop jacks that are part of the audio signal path, the dirty contacts will cut or reduce the signal level down to the point where there will be as in your case, no signal from the amp at all.

Good luck.

[TomCarlos]

Troy... and future visitors.....

Some videos to watch for basic amp maintenance -

10 WAYS HOW TO FIX A GUITAR AMP AUDIO NOISE, SOUND DROPOUTS, NO POWER

Amplifier Service & Maintenance | LECTRICareŽ Music Electronics

Dr. Z AMA: "Yearly Amp Maintenance"