Switching PSU Theory of Operation / Repair Tips & Techniques

From: Douglas Quebbeman <dhquebbeman_at_theestopinalgroup.com>
Date: Thu Jul 27 09:32:42 2000

> On Wed, 26 Jul 2000 22:21:47 +0100 (BST) Tony Duell
<ard_at_p850ug1.demon.co.uk> wrote:
> > > The electrolytics are Mallory CGS 2900MFD 250VDC. The one on the -
side
> >
> > And there's another clue. Those capacitors are rated for 250V, and yet
> > you're seeing 280V across them. While they'd probably stand that for a
> > short time, not computer power supply would be designed to work like
> > that. So either there's a fault, or you're not measuring the voltage you

> > think you're measuring.
>
> I think Tony's spotted a very strong clue, here. Kinda
> makes me suspect that the voltage measurement is going
> wrong for some reason. Could there be some non-DC
> component that's making the meter read wrongly?

With the PSU disassembled, and the secondary out of the way,
I'm going to take fresh reading on the primary today at lunch.

I'll post the results when I get back to the orifice, er, office.

-dq
Received on Thu Jul 27 2000 - 09:32:42 BST

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