Safety switch to drain filter caps?

[Steve Conner]

I've always just used one resistor for the entire amp, 100K 3W.

The two first amps I built had the main filter caps in series stacks, so I put a 100K 3W resistor across each cap for balancing, and these also function as the bleeders.

My new stereo amp takes a good minute to die after the standby switch is flipped, so I'm thinking to try the "dump" trick that was described here.

[defaced]

Also, is 220K 2W pretty standard? Any *other* recommendations?

You want a value that's big enough not to cause a large current to ground and thus an associated voltage drop, but you don't want something too large that it takes forever for the caps to drain. I use 220K 2W because it was the value used for balancing resistors in a Peavey amp I disassembled.

If I ran the math for Ohm's law and the discharging time constant for the RC circuit I might come up with a different resistor, but this one works good enough for me.

[iwantmypie]

My Peavey Mace has those 220k resistors installed parallel with my filter caps. According to the schematic they are only 1 watt but they get the job done. When I turn the amp off and flip the standby switch off standby the caps completely drain in a few seconds. Now I believe my filter caps are original and probably almost 30 years old so I'm not sure if they are suppose to drain that quickly but they do.

[Enzo]

That's what they are supposed to do.