Bleeder resistor

[238]

Working on some old Maco amps. Adding bleeder resistor. What value resistor should i use for the 100uf x 450v caps? 238

[MDYoungblood]

The value of the resistor is determined by how long you want it to take to bleed off the capacitor.

3's

Greg

[238]

I thought there might be a common size most builders use. 238

[MDYoungblood]

The lower the value the faster the drain, 22K would take about a minute, 1M about 10 minutes.

3’s

Greg

[Crusher]

For Bleeder resistors, I generally use 100K ohm 3watt metal oxide. If it’s a very long string of I use 100k 5watt metal oxide. But you also have to pay attention to voltage rating.

That Maco amp, how many caps are in series? 3-4 ? If so, 100k 3W will be ample.

[Crusher]

Just be careful in there, not only of the HV plate capacitor bank. Some other circuits like control voltage for relays in certain amps will be 110vdc and don’t have a capacitor across that cap either. I found out the hard way myself years ago the hard way. Just be careful

[238]

I know what you mean. The cap i used on the negative DC bias discharged when i touch the resistor with the solder iron. It scared me. These are the small Maco amps. The one & two tube amps. They have 2 100uf x 450v caps in series in them. 238

[Crusher]

100k, 220k or 470k ohm work. For the small Maco amps.