I've received an SB-220 from a friend in non-working condition with the advice
that the filter caps were bad and that I should get the replacements from
Harbach, which is exactly what I did. After installing the new caps from
Harbach and powering up the amp on 240VAC the amp did nothing more than throw
the circuit breaker. After a couple of attempts while trying to troubleshoot
various things the smoke escaped from the transformer. As I understand it,
this sort of behavior is non-optimal and probably indicates that there is a
problem with the plate transformer.
In retrospect, I realized that I probably should've tested the old filter caps
before I had ordered replacements. After checking them with the cap meter,
they all tested good. At this point, my main question is what is the best path
to determining and resolving the problem with the plate transformer. Can
anyone give me specifications on what the resistance should be on the primary
and secondary? I assume that my problem is a short somewhere and that I should
be able to determine that with an ohm-meter. Assuming that there is a short in
the transformer, is there anyway to get the smoke back in? Is it possible to
fix by hand? I suspect that even if it is possible to rewind it by hand that
it would probably take more effort than it was worth. I've seen original (used
or NOS) transformers for sale for around $150 and I know that Peter Dahl makes
one that runs about $255. What would be the wisest course of action at this
point. Any advice would be appreciated.
Thanks,
Heath Albritton (KG6GTX)
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