Draining current before working

[EWBrown]

If you discharge any of the caps in the PSU string, it will discharge them all, I generally go for the cap closest to the rectifiers. The black or white stripe is generally the negative side. You can use any "solid" ground point in the circuit, it doesn't really have to be the cap's negative terminal.

A relatively slow discharge is better than "slamming" it to ground and all the sparking and arcing.

/ed B in NH