Switching PSU Theory of Operation / Repair Tips & Techniques

From: Douglas Quebbeman <dhquebbeman_at_theestopinalgroup.com>
Date: Fri Jul 28 07:03:29 2000

> > Well, the entire large PCB containing the secondaries
> > is completely disconnected, removed, and set aside.
> > In addition to the cable carrying +ve and -ve to that
> > board, there are a few (two? I should have written that
> > down) other cables that connect the two boards. So my
> > only other theory is that some of what's on that board
> > is involved in some kind of feedback process with the
> > primary to step it up even higher.
>
> _Very unlikely_, since the capacitors are only rated for 250V.

Ok, I grok this.

> (b) aren't you using a good old electromagnetic meter ?

Until I get the Fluke fixed... yup.

> > Are you sure? My Alled Electronics catalog has thermistors, but only a
> > few in the catalog is as large as these are- about 1 inch diameter.
>
> OK, they're special thermistors :-). They are low resistance, and they
> are designed to carry heavy currents (unlike, say, the thermistors used
> for temperature measurements). I've seen thermistors used like this in
> PSUs before...
>
> And apart from that, a disc ceramic capacitor, or an MOV, makes no sense
> electrically here.

Like I said, I'm an analog idiot!

-dq
Received on Fri Jul 28 2000 - 07:03:29 BST