SB 200 Power Output

[Mark Graalman WB8JKR]

  Sounds like you might have a diode bank out in
the HV doubler, or a capacitor bank bad.
 I find it quite odd that the
plate current would stay the same, it must drop
with the B+ drop if the drive stays the same.
 If your B+ is dropping you should be seeing an increase
in grid current if the drive is the same. Could be the
metering circuitry is lying to you, but that wouldn't explain
the power output decline.

Mark  WB8JKR


On Mon, 12 Feb 2001 14:16:20 EST John Barkow <KD6PT at AOL.COM> writes:
> High Gang: Several months ago I purchased an SB 200 amp in pretty
> good
> condition. Power output was about 400 watts DC on all bands,
> including WARC
> bands which wasn'nt too bad.  I have installed a Harback power
> supply board
> and "soft key" and it works great with my Kenwood 570..Lately the
> power seems
> to be dropping off and is now down to about 300 Watts.  The HV
> decreases from
> 2300V to around 600 volts when the amp is keyed but plate current
> stays
> constant.  I feel that the tubes are probably the problem but I
> could be
> wrong.  Let me know if any of you have comments on this before I
> invest in a
> new set of tubes.
> Thanks, John kd6pt
>
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