On Sun, Apr 25, 2004 at 02:59:20AM -0800, Richard Purdie enlightened us
thusly
> Friedel Bruening:
> > There must be at least one feet back, normally there are 2. The
> > first will be the current measurment of the switching transistor,
> > the second mostley comes from the secondary side, which is got to be
> > isolated, the use opto's most of the time.
>
> It doesn't have to be isolated and a low voltage DC/DC switcher
> probably won't be. If the primary is at mains voltages you usually
> need to do so for obvious reasons.
This guy seems pretty paranoid. I'll bet they are isolated. Surges could
hit be high on this 24V and in the outputs. I can't swear to anything,
though.
>
> > Have you verified the switching cap to have low ESR ? I had
> > experience with faulty switching transistors, which looked just fine
> > to simple checks, but just did'nt work in this PWS anymore.
Caps seem fine. Analogue Signature Analyser helps there. No short
anyhow. Everybody is mentioning them, so I'll be check thoroughly.
>
> I've repaired a few SMPSs (and designed a few). Top of the list of
> failures I've seen are capacitors. Either the ouput voltage smoothing
> ones or ones which stablised the voltage supply to the controller on
> the primary side. Next on the list is shorted switching transistors
> or ones that have otherwise failed. I've also seen a couple of
> unstable control ICs (they shows signs of working but weren't 100%
> right) where the PSU worked once they were replaced.
>
> The inductors normally survive but I've never dealt with one like
> yours.
I've never dealt with one like mine! Nobody has. That's the problem.
--
With best Regards,
Declan Moriarty.
--
Author: Declan Moriarty
INET: [EMAIL PROTECTED]
Fat City Hosting, San Diego, California -- http://www.fatcity.com
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