[Amps] Glitch Resistors - Again

[Charles Bibb]

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