From: John Woodgate
Subject: Re: Strange failure mode in switchmode power supplies: Followup
Date: Sat, 21 Sep 2002 07:31:50 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Sat, 21 Sep 2002 08:19:25 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Harry Dellamano
wrote (in )
about 'Strange failure mode in switchmode power supplies: Followup', on
Fri, 20 Sep 2002:
> Exactly, normal operation as you point out we have no problem but if the
>this particular line may have gained some inductance then we have a problem.
>This is not a normal line. We are looking for needles in haystacks,
>something that is not on the original prints, parasitics. The chances of
>this guess being true is probably one out of twenty but you have to guess at
>something, following your nose with good measurements techniques until the
>truth is learned. When we do learn the truth, we will all laugh at how
>stupid we were and should have found it sooner.
> Oh, by the way, if that Pole Pig is a step down then the primary is much
>higher inductance and if one was left in series with this line then we are
Any such impedance in series with the line means that there can't be 120
V downstream of it when there is any load on the line. The OP would
have noticed that: lamps getting dimmer and dimmer the more that are
switched on, for example.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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