How do I discharge the capacitors in my PS audio P20 ?

Erik has the correct answer. Then after the wait place a pair of pliers across the two terminals of the capacitor to make sure it has discharged completely.

noromance... this is do as I suggest not as I do. I have a 12 guage wire open at both ends taped to two round dowels and I just touch them to each pole. You do this at your own risk as the capacitor may go away. I haven't had it happen but it can. Now if I had suggested what I do, I would have 30 on this blog telling me how dumb I was to suggest such a thing.