So I rebuilt a Dynaco ST-35 and today it has hum and buzz equally in both channels that is really bad in a normal configuration with interconnects connecting it to a Bottlehead Bee Pre preamp and hooked up to Altec 846A speakers. Last night it just had a little hum and buzz in one channel. This is what I have done to trouble shoot just not sure what it means (and I will list in what I think is order of importance):
- Shorting plugs in the RCA jacks: Hum and buzz pretty much gone. Maybe a tiny bit of buzz.
- Same set-up upstream, same interconnects running to different amp: no hum or buzz.
- Take out interconnects and run Dynaco with RCA jacks open: slight hum and buzz both channels, hum a little worse than buzz.
- Different set of interconnects to preamp (which is off) with amp plugged into various outlets: very bad hum which overwhelms any buzz that might be there plus some clicking noise.
- Running a jumper from amp to preamp makes no difference.
- Lifted ground from power cord using a cheater plug into a power strip, bad hum and buzz, no clicking.
- Radio Shack ground tester shows good ground in the three outlets used.
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