Having finally finished my 813 amp and put it into service, I took my SB-1000
to the bench
to find out what had caused the loud ZZZZAAAP and blew the fuses last week.
I found that one of my clever mods was not so clever at all. I had decided that
the tank
coil was too close to the steel top cover, and this was reducing efficiency on
160 meters.
So I moved the tank coil about 1/4" farther away from the cover.
I am not sure that it helped on 160. But it placed it closer to the plate
choke. Turns out
it was a little less than 1/4" away.
This worked fine for a long time. But last week I was trying to work something
on 30
meters and I wanted my full legal 200 watts instead of the measly 100 that
comes from my
K3. 3 dB could make the difference. Either the choke had a resonance that
vaporized the
wire which started the arc, or the small gap happened to be near a new hot spot
on the
choke, but ZAP.
Some of my happier mods were the addition of a glitch resistor and back-to-back
1N5408
diodes across the meters, so nothing else was damaged. A new choke is on the
way from RF
Parts.
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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