Help with hum in Vox AC15H1TV

[01redcobra]

In bridging the resistors R16 and R14 the hum is gone. I have not tried the C25 and R36 grounding yet. The filter caps are on that same wide center track although it may be hard to tell in the photos. Thanks so much. This is the most productive motion I have seen in a while on this amp. I did pull the VR4 from the chassis again and tried leaving it floating and also grounded the case to the leg ground and the hum was there. So far the best reduction has been the grounding for the grids at the PI. But removing V3 has also just about eliminated it.

[J M Fahey]

So far the best reduction has been the grounding for the grids at the PI.

Then the *last* idea I have in my bag is trying to float the ground of V3, and the volume pot and connect them to the PI grounding point, making a mini star ground for them.

[01redcobra]

My last move with the amp was replacing the leads from the VR4 volume pot with single cond. shielded wire. It had been 2 cond. shielded. I grounded the shield to the PI grounding point. Also did the same with the leads from the VR5 bass pot. Also relocated the C22 cap to the legs of the pot. It had been dangling from the grid lead above the board, just looked like an easy place for the hum to enter. Seems like it may have attenuated the hum a little, but it is still there. I've pretty much run out of all ideas also. If anyone ever comes up with a fix, please let me know. Thanks to all that have been involved with this thread! This forum has some of the best people in the repair trade out there!