Paul wrote:
>A friend and I are putting together an 8877 amplifier for 160 through 20 m.
>Power supply puts out 4200 volts no load. Plate transformer is very heavy
>(guessing about 100 pounds)--oil-filled filter capacitor is 25 mf. A 25
>ohm, 50 watt glitch resistor is installed in the amplifier.,
>
>We have been experimenting (on the bench, amplifier not connected) with a
>triggered spark gap to blow (and I do mean blow!) a fuse of #39 wire
[lots of ingenious stuff]
>Any help and educational comments and suggestions would be greatly
>appreciated. (Why are we doing it this way? Because my friend thought it
>might work and be cheaper than thyristors--but if it won't protect the
>8877, then we are looking at a very false economy)
Quite so. The ultimate test is to see whether you can crowbar the HV
supply with another very thin fuse wire and have that wire NOT blow
before the supply is shut down.
For this test, Eimac recommend a 6-inch length of #40 AWG soft copper
wire (Application Bulletin #17, the same one that recommends glitch
resistors).
The spark gap methods may be workable, but the thyristor circuit is
almost as simple, and it's <quiet>... think of the laundry bills.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
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