john <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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At 02:03 PM 11/6/2007, Mike Bryce wrote:
the reason is not really clear..
but here goes
if there is a fault in one or both of the tubes, or a short circuit
someplace on the +2700 volt line
this resistor acts like a fuse and pops open.
And it's quite handy!
I have (ahem) tested this function on a 30L1 that I was working on last
year. It uses a cluster of 2W carbon comps as the HV fuse. Since I forgot
that the Collins has multiple spring loaded interlocks on the B+ when it's
out of the cabinet, I was able to fully appreciate the beauty of these
resistors . After the smoke cleared, I was able to see that the resistors
opened and perhaps saved the transformer from my stupidity!
"Normal" fuses ...the 3AG types, are not rated for HV, and may not clear
when overloaded with such HV. This arrangement is also a good surge
stopper....
Cheap insurance
John K5MO
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