I was thinking I was finally through with this Ampeg from the prior thread (ground loop hum...), when it started popping like static discharge.
If I pounded on the chassis, the popping got worse. I isolated it to the main amp chassis.
It turns out that if I grounded the metal base on one of the 6550 tubes, the popping went away.
I never realized that on some of the versions of the 6550's have that metal base connected to pin one (not all of the ones I have, have this connection). I guess that helps shield the longer connections to the actual tube inside.
Turns out pin one was not making good connection to the tube socket. I tightened that pin in the socket & the problem was solved.
It still ain't over...I've got other problems with the -15V. see other post...glen
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