Bassman 50 grounding

[labb]

This thing has a lot of ground points including the brass plate under the pots. It has to be a hummer. Probably the reason it has the humdinger on the heater wires and the hum balancing circuit. I really want to try to clean it up but guess I’ll just have to wait till I get it up and running to really see what it does.

[pdf64]

This thing has a lot of ground points including the brass plate under the pots. It has to be a hummer.

That ain’t necessarily so.

Probably the reason it has the humdinger on the heater wires and the hum balancing circuit.

No, humdingers help to minimise the interference into the signal path caused by (early stage) valves with imperfect heater to cathode insulation.

I really want to try to clean it up but guess I’ll just have to wait till I get it up and running to really see what it does.

The original design was very probably fine. Messing with this stuff before you found a fault and correctly identified its root cause will likely as not cause hum.

[sluckey]

I’ll just have to wait till I get it up and running to really see what it does.

Good idea. Fix what's broken then reevaluate.

The grounding on that amp worked just fine when it was new. I'd leave the grounding alone. The brass plate has been known to cause some issues, but nothing that can't be cured by reflowing the brass to chassis solder with a big iron or Weller D550 gun.

The humdinger is an improved method of dealing with heater hum and the hum balance (really bias balance) deals with hum due to unmatched output tubes. Neither are related to poor grounding.

[PRR]

A humdinger can reduce several kinds of hum.

Unless you can SEE the hum-current in the chassis, or are doing a TOTAL rip-out, leave the multiple grounds as they came from the factory. The old guys were not so dumb.