Re: [CAD_CAM_EDM_DRO] blown rectifier bridge question

On Wednesday 25 August 2004 07:27 pm, docholliday02743 wrote:

> Help! I am assembling my control box and have installed and wired the
> fans and the toroid primary. I gently secured the rectifier bridge
> (from mouser, 25 amp 600v) I wired the 55vac to the a/c side of the
> rectifier and was going to read the d/c voltage at the d/c terminals
> before hooking anything up (capacitor, etc..) instand loud hum and
> shorted rectifier bridge! measured resistance across a/c terminals of
> rectifier after this and it is shorted (0.2 ohms). Figured bad bridge,
> installed 2nd bridge (this time testing resistance prior to hooking
> up, and instant short again. It isn't the secondary of the trans as
> that tests fine and there is no short if I plug in the primary from
> the trans and leave the secondary not connected to anything- good a/c
> output and no short. I am wondering if the capacitor MUST be installed
> before hooking up power?
>
> Help!

I'm not sure what you're looking at there, though it sounds like a wiring
error...

What I would suggest is that if you want to do some testing, particularly
with no load across stuff, that you put a light bulb (60W is a good size to
start with) in series with the transformer's primary. If there's no problem
it should stay out or at most dimly lit, if it comes on bright you know you
have a problem and it will limit the current that flows.

How did you have things connected when you let the magic smoke out?