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From: firstname.lastname@example.org (Tim Shoppa)
Subject: Re: Can a transformer fail?
Date: 16 Dec 2002 05:36:24 -0800
NNTP-Posting-Date: 16 Dec 2002 13:36:24 GMT
"be jennings" wrote in message news:...
> Ok I've got a car amplifier from a friend that runs on 12v. Basically it has
> four channels and one toridal transformer per two channels I think? Anyway
> at one side of the coil about 23V AC go into it and I get around 80v ac out
> the other side. Now with the other transformer on the otherside exactly the
> same goes in however I only get about 2v AC out?? can anyone explain? I've
> reversed the transformer around and then I only get about 0.2v AC so my
> question is can the transformer fail?? if so how do they usually fail? and
> can they be repaired or tested some how??
You're looking at a switching power supply in the amp that boosts the
voltage which is then rectified, filtered, and used to power the final
You're taking advantage of one fundamental advantage to stereo repair: you
have one good channel and one bad channel to compare and contrast. And
you seem to have zeroed in on the problem.
If you're getting very low voltage on an output, it is possible that the
transformer has failed (cracked core, shorted turns, open winding, and
two windings shorted to each other are all possible) but in your case I
think the problem is that the something after the transformer has shorted
out. For example, the rectifier and/or filter cap on the output would be
good things to check. The final output transistors may have gone bad with
collector-emitter shorts, too.
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