>
>
>In the L4-B power supply, Drake used an IRC type BWH/SPH "fail-safe"
>resistor (0.82 ohms/2W) as a fuse to protect the diode strings in the
>event of
>a short or closure of the RF deck cabinet interlock.
>
>The resistor is still a current IRC product (as a type SPH device), but is
>not a
>high demand item, and is out of stock at every IRC distributor I have
>checked
>(including Drake). So while it is "available" it is essentially
>Unobtainium.
>Newark wants a minimum order of 250 each to even go ask IRC for a
>production run. At $0.44 each, that makes a pretty expensive price for
> ONE ;-)
>
>So the question. Is there some generally accepted alternate method for
>protecting HV diode strings?
Yes. The ''glitch'' resistor. A glitch resistor limits fault current.
It is not a fuse. It must be able to discharge the hv supply filter C
without sustaining any damage.
> A wire fusible link, perhaps?
A fusable link does not limit peak fault current - and that is the thing
that causes damage. The right place for ordinary fuses is in the 240v
line.
>Or is this even
>considered necessary?
A glitch R is totally unnecessary if you have a free supply of new tubes,
Grant. cheers
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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