Hi, All
I've been reviewing recent posts about glitch resistors.
This past summer, I re-built the P/S to a Drake L7 amp. Re-built may
be the wrong word because the only thing from the old supply that I
used in the new supply was the transformer and the glitch resistor!
The L7/PS7 uses a 0.82 Ohm, 2 Watt IRC wirewound resistor in the B+
lead, the theory being that during a HV fault this resistor will
explode, thus interrupting the HV supply (much like a HV fuse) and
therefore preventing further damage. Some more sophisticated HV power
supplies use a current sensing circuit and a wide contact spaced
relay (or vacuum relay) to do this.
Most of the posts I've read, though, favor the use of a larger
resistor (approx. 15-20 Ohms, 25 Watts or greater) in the HV lead to
act as a sort of "brute force" limiter against a HV fault.
Since I've got to go into my P/S anyway to replace the cooling fan, I
thought I'd replace the small "disposable" glitch resistor while I
was at it. But then I got to thinking. Instead of replacing the
smaller glitch resistor, why not just add the larger one, and have
both in series? Wouldn't I get the best of both worlds, so to speak,
getting both protective actions?
Is there any down side to this approach? I can't think of any.
73,
Charles
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