Lousy Legend Reverb Hum/Buzz

[drewl]

Got an A30 with hum/buzz noise from the reverb return amp.

It's not the tank, or the cables, I replaced them as the return shield was tarnished like these things get, someone noted in another thread the components weren't sanded before installation so they get corroded.

Filter caps are good, IC3 is good, I re-flowed pots and jacks and return amp components, still has noise.

messing with the return amp shield ground lowered the 120hz buzz, but it's still pretty noisy.

There's something flaky going on with the two different ground planes, as you can see some stuff is grounded to the chassis, some to the filter cap ground plane.

other than that, the rest of the amp works fine and is pretty quiet.

What the heck am I missing?

Thanks.

[Mick Bailey]

If you unplug the return and short out the plug does it still make the noise?

[Jon Snell]

120HZ buzz is smoothing issues in the power supply or a smoothing capacitor on the wrong ground.

[drewl]

Hmm, shorting return plug it still had noise.

Running a wire from HV center tap to R36 ground lowered buzz, even though I cleaned and tightened all the plugs and connections.

The return amp is IC2, not 3 as I thought.
But- IC3 was causing noise, I replaced it and it's quieter.
Not perfect, but much better.