Peavey 5150 Combo Issue

[Axe Slinger]

I'm having an issues wher the per gains are working but the EQ and Post gains are not doing anything. I just replaced the tubes, but not sure what's going on. Does anyone have any ideas?

[Jazz P Bass]

Did everything work before you changed the tubes?
Do the "Rhythm/ Post" & the "Lead/ Post" controls do anything?

[Enzo]

If the post and EQ controls are inoperative, I suspect you may have lost the ground conection to them.

[John G]

Hi,
I have just finished repairing the same amp (see the other current 5150 thread) similar problems but mine had a very high noise level as well.
C57 PSU cap was the cause, O/C................... so I replaced it and now all is well ??
V2+ HT node is shared by the post Effects return stage and the front end pre tubes, so if C57 goes open, audio signal can get on to the V2+ PSU node and then leak into the post effects stage and effectively bypass all in between ...........the eq, M/Vs etc.
Thanks
John G

[Axe Slinger]

THank you for all of your help, it was a bad ground, but now I have another issue. Now when I turn the Lead Pre up past 5 I get a squealing noise, even if I have the valume on the guitar turned off or the guitar isn't even pluged in. It's not a feed back sound.

[Enzo]

Well, it probably is feedback, just not through the speaker.

First verify you don;t have a very microphonic preamp tube.

Next try redressing the ribbon cables.

[Axe Slinger]

Thanks again for all of your help, I checked the tubes and they where fine. I started pulling the cables one at a time starting with the reverb and when I removed the reverb cable and turned it on it stopped. I pulled the tank and refitted all the wires and put it back on and re seated the cable to the board and all is fine now. hmmm, lol.