I sent this a copule of days ago but never showed up on this reflector,
So here it goes again. Any help appreciated.
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Hello folks !
My SB200 bit the dust last night after what seems to be an
arcing. I was tuning up the amp at 15m band using full 100 W
drive from FT-1000MP, and there was this 'bzzzzzzz' sound and
the output power became half what it used to be. The typical
output was 400-500 W on 15 m band when it was normal and now
it's less than 200 W and unstable. The plate current reading
is about 70 % of normal and grid current goes over the full
scale of the meter. The HV reading is also about 70 % of what
it used to be. I have not yet inspected the interior of the
amplifier for any tell-tale signs, but the filaments of the
two 572Bs looked OK from outside.
I am no expert in vacuum electronic circuits although I can read
circuit diagrams. I installed
Harbach soft key mod, etc. with no problem but that was an
easy one, I suppose. Now I need the input of the collective wisdom of
this reflector to repair the SB200. What should I check first ?
I have digital multimeter and soldering iron available, but
nothing much else.
Any input is appreciated.
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¹Ú ¿ë ¼· (Yongsup Park) | +82-42-868-5397(O), 5032(F)
Surface Analysis Group, KRISS | park@kriss.re.kr
P.O. Box 102, Yusong | http://www.surface.kriss.re.kr/~park/
Taejon, 305-600, KOREA | Amateur Radio: DS3GLW
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