Amp is in Coma or Dead

[hh73]

Peavey Valveking 112

Sometimes while playing, if I ever hit the strings hard (to get a loud sound) the sound in the amp would cut out and not come back for a few seconds.

The last time that happened, the sound has never come back. It's been about a week. What's the problem? Can it be fixed?

Its not a problem with the speaker. When I hit the reverb can with my hand, I can hear the springs bounce in the speaker. Something is wrong somewhere else.

Its not the guitar. Its not the guitar cable. I already double checked.

[hh73]

I should mention this only started happening after I changed all of the power tubes and pre amp tubes. I have checked to make sure they are seated correctly. They are all electroharmonix

[hh73]

I just checked the effects loop. It works perfectly. When I turn on an effects pedal, I get the familiar "hahhhhhhhhhhh" sound. There must be something going on at the input jack for the guitar. Do you guys have any suggestions on what might be wrong? How to fix it? Or do I give up and buy a new amp?

[JohnH]

sumgai is likely to be best placed to make insightful suggestions on amp repair. But just skirting around it:

If you plug a guitar into a pedal and then that into the FX return, does it work fine?
Are all the heaters in the tubes lighting up?
Other than this cutting out effect, does the amp sound normal in other ways?

[hh73]

Yes, plugging the guitar directly into the effects loop makes it work.

All three pre-amp tubes are getting warm. One of them is actually getting hot. The other medium. The last one is luke warm.

Only the hot one is getting slightly glowing. I'm not sure if the other two are exhibiting any light.

Amp sounds totally normal when the guitar is plugged into the effects loop.

I tried "rotating" the tubes (a 3 way rotation, pulling them out and switching their positions) and that did not fix anything.

[hh73]

"Amp stutters or cuts out when driven really hard: overdrive is causing the output tubes to go into grid blocking after being over driven; this is caused by the signal causing a temporary bias shift."

This kinda described my problem before the amp got so bad that it stopped working altogether. Whenever I would hit the strings particularly hard, the amp would cut out.

At the end of the day, I want to know if this is going to be the kind of easy repair I can do myself without taking the amp apart. If its not, I think I have to buy a new amp, seeing how I don't trust the repair guys in my area.

[hh73]

PROBLEM FIXED!

I swapped out one of the pre-amp tubes with an old tube I had saved. Fixed the problem right up!!!!