Discharging power capacitors

Depends on the Voltage - if a tubed amplifier you should be EXTREMELY careful - voltages inside are lethal - always work with one hand in your pocket.  

But as described above use a bleeder resistor - 1Mohm definitely if a tubed Amplifier , a SS with much lower voltages you can use one of considerably lower resistance - I for an example use a 25W 50 Ohm resistor for bleeding the rails fast when working on my amplifiers, rails are between 35VDC and 65VDC 9 (The internally installed bleeders are 22K)

Best of luck 

Peter

I'll just add to the good suggestions above that with some types of capacitors it may be a good idea, after the capacitor appears to have been discharged, to remove the voltmeter or other means of discharge, wait a while, and then reapply it for some amount of time.  The voltage on some capacitors that appear to have been fully discharged can subsequently "bounce back," to a small fraction of the original voltage but one that nevertheless may be significant, as a consequence of dielectric absorption.

Best regards,
-- Al

I remember back in electronics school a couple of guys playing catch with charged caps.  smaller ones...

I use 1mOhm resistor with wire leads. Usually resistor worms up when large cap is discharged. Small caps do that in instance and not considerably dangerous if they even discharge on you.

If there is not a bleeder resistor already installed into the power supply circuit, I put a volt meter on the pos and neg leads and this usually drains the voltage. It has the advantage that you can actually see the voltage drain away, which will verify that you are now safe to work on the circuit.