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

The capacitors should be discharged to ground. You don't use a multimeter for that, other than perhaps to test the caps for voltage afterwards to confirm discharge.

Assuming you don't have a 10watt 1k resistor on hand, you could use a 40w light bulb.

@hiendmmoe

I am interested in this as well.  This link seems to give a good explanation. 

https://www.nextpcb.com/blog/how-to-discharge-a-capacitor-comprehensive-guide

The nextpcb article above says to short caps with a screwdriver. I do not recommend subjecting power capacitors, especially electrolytic ones to a dead short as they may be permanently damaged.

It's possible that the PS Audio unit already discharges the caps on power down. Measure with DMM set to Vdc and relevant range. 

You culd also just unplug it and wait 24 hours

Ask PS Audio 

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.

Power down. Unplug from the wall, turn power switch back on. This should drain any residual charge left on any power supply caps.

bmbmzig

Power down. Unplug from the wall, turn power switch back on. This should drain any residual charge left on any power supply caps.

No. That will recharge the capacitors.

Cleeds, et. al. - 

I don't know if there is any standby power battery in the described device, but if the unit has been unplugged from the wall, ANDS REMAINS UNPLUGGED, I am not sure where the power is coming from to recharge the capacitors when the power button on the device is pressed. Press and hold for a few seconds may be worthwhile. 

This procedure is standard practice to ensure that a computer system's PSU and other components are fully discharged before pulling circuit cards, drives, etc.  Also, since the user may not know the polarity of the electrolytics in question, they should watch carefully for ANY change in readings on a test multimeter - either up or down scale - which would indicate that some residual charge remains in that part of the system.

Finally, testing should be done on a DC range similar to the rated voltage indicated on the side of the capacitor being tested.  More, and you may not notice any "twitch" of the needle, and less may result in damaging the test instrument or device being tested.  Also, given the internal workings of the test device and the voltages involved, there may be only a momentary indication of residual charge, not a steady-state reading.  

@frankmc195 If I had to wait 24 hours every time I needed to work on a tube amp...

Erik has the correct answer. Then after the wait ...

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.

How will the capacitors be recharged with no power applied to unit. I worked as a audio repair tech for 40 years and it always worked to drain off power supply charges 

bmbmzig

How will the capacitors be recharged with no power applied to unit.

They won't, of course. I misread the question.

Shorting a high uF cap directly is a bad idea. You can in fact ruin an otherwise good cap.

Also, worth noting the voltage rating on a cap. If it’s 50V say or less, it’s not that dangerous.

If you don’t have a 10W resistor, just use a bigger Ohm resistor and wait longer. What’s the big deal?

Lastly, why on earth is someone who doesn’t know how to measure or discharge a capacitor safely getting into the guts of an appliance?

Just curious. What "wire" came loose, and why? Was this a quality control issue with PS Audio? Wires "coming loose" in a power regenerator, having high voltages inside don't sound good. An end user who is not a legit electronics tech attempting to mess around "fixing it" doesn't sound like the smartest idea either. Just sayin'. If you are concerned about safety (and you SHOULD be!) take it to an electronics tech and get it done right with some peace of mind. 

+1 @erik_squires .

I am not an electrician, but thanks to the seniority bump & bid system I did a few tours through the electric shop of a major airline. We used what I remember being called a "shunt" to discharge all caps. (It is possible I remembered the terminology wrong.) But basically it was a wire with a probe on each end and a resistor soldered in the wire (obviously between the two probes). What everyone did, so therefore what I did, was when working on something with caps involved was, put one probe on one lead of the cap and the other probe on the other lead of the cap, and that would discharge it. I did just dig out the "shunt" that I took home and kept for my own use and measured the resistance, and I read 123.8 ohms on it.

Once just for the helluvit, I decided to check the caps on an old preamp that I have, and for that I used this handy-dandy cap checker from China that I bought on Amazon. However, I forgot to discharge the cap I was checking first. The cap did discharge, but it cost me my handy-dandy cap checker.