Quote Originally Posted by irving2008 View Post
Bleed resistors are there for safety. You might never power the supply on without the steppers connected but I can't know that and I would never advise building a hi-voltage (>48v) supply without them. Leaving them out isn't best practice (it ranks with wiring e-Stops with 230v and having plugs on the 'live' side in my book) and I've been caught out by that before. For the record, I've been in electronics manufacturing on and off for over 30y and have seen most levels of stupidity :)
Couldn't agree more and here's an example of why.!
I've just acquired an old cnc lathe out of a school and been ripping it's guts out has it runs a bespoke control/software and I want to run Mach3.
This thing has 3 boards Control boards, PSU board and spindle board. I'm keeping the PSU and Spindle so after pulling the control board out I was messing with the spindle board trying to work out what wire goes where when I got a pretty wicked kick I wasn't expecting seen has it wasn't plugged into mains.?? . . . .Yep it's got toroidal PSU with no Cap drain.

Not enough to hurt me but woke me up good and that was only small PSU running at 36V ish with relatively small caps.!!

SO I completely agree with Irving and always build them into my PSU's..!! . . Now the only thing I don't like about Irvings way is that the resistors are permanently draining while the machines running, this creates heat while running so warms the control box and therefore the drives etc.
I'm a bit Anal with my control box and build them with relays and full safety using 24V and control lots of things with relays, one of these is a NC relay which kicks in and out a resistor so it only drains when off.!! . . No such thing has being too safe IMO.