Discharging capacitors

[SpareRibs]

Hello,
I know this is going to be a dumb question, but is it necessary to discharge each and every one of the capacitors before working on an amp? Is there a point where all of the capacitors can be done at the same time? Also are there any web sites which cover this subject? I know safety is the number one concern when working on electrical devices. Thank You!!

[Enzo]

We are probably talking about the high voltage caps - the "B+."


They are all connected together through resistors in most amps. IN some amps, there may be caps on both sides of a standby switch, so they may not then all discharge together. But if you power off and unplug from the wall, but leave the standby switch - if there is one - in the ON position, then discharging the main filter cap will usually discharge the rest.

In any case, you ought to have a voltmeter out and watching the voltage in the system anyway. Then you will know if things are discharging nicely.

Once it gets down to 10v or so, it won't hurt you. Getting absolutely every last volt out of it is not necessary, and the distributed capacitances in the circuit can store bits of charge and thwart that too.

[Chuck H]

In fact, even if you were able to discharge to 0V, the caps will come back up to ten or more volts once the bleed circuit is removed!!! I don't worry about it much and I haven't been shocked (in a long time) If it makes you feel better you can just leave the bleed circuit in place until your done working on the amp. Sometimes I do this because it's not in my way and I simply don't bother to remove the aligator clips.

[Enzo]

If interested, look up "dielectric absorption."

SOmetimes referred to as capacitor memory informally.

[tedmich]

If interested, look up "dielectric absorption."

SOmetimes referred to as capacitor memory informally.

I have a flawless memory of every time a cap has shocked me.... 220k 5w resistor on INSULATED alligator clips works well for me!