Ampeg M15 hum

[drewl]

What do you guys do with the old Ampegs that don't have shorting jacks?
Do you replace them and lose the stereo jack or is ther a better way to get rid of that hum?
The filter caps and PI inverter coupling caps were replaced but this amp still has a bit of ripple on the output tube plates and ground hum as you turn up the volume controls.
I had dc leaking through the trem coupling cap, but replacing it didn't help with the hum.
Also the output cathode cap was replaced.
I'll check the preamp coupling caps to see if they're leaking dc.

[Alex R]

I reckon 4 or 5vDC of ripple on the B+ is normal.

[drewl]

yeah it's normal ripple.
If I remove the 1st preamp tube hum goes away, I swapped it around with the other two 6SL7's but the hum is the same.

[drewl]

UUGGHHH!!
Dang, I still have some 120hz "buzz" with the volumes cranked.
I have some 6SL7's coming, I'll try that.
Any other ideas?