Hi Steve,
>From what you have said and done so far I would guess that you have some
weak tubes. One seems to be weaker than the other. You should get around
600 watts or so out of the SB200. Plate current should be around 500 ma.
Don't rely too much on the plate voltage reading that you see on your
meter. The divider resistors in there change over time and can throw the
reading off some. They seem in the ball park.
There is an 800 volt transformer in there with a voltage doubler. At
rest that should give you about 2200 volts. Under load around 2000
volts. Those voltages may vary some depending on your line voltage drop.
The amp efficiency runs around 60%. Lower on 10 meters.
73
Gary K4FMX
Steve Woodruff wrote:
> Thanks to all those who have replied direct
> and also privately. I did find a resistor
> on the anode clip had one lead snapped. I
> am not sure whether it was like that or if
> it happened while i was removing a tube.
> Regardless, i did the "tube-swap-a-rama"
> tests and came up with these results:
>
> SOCKETS: L R Pout
> ==============================
> Tube(s) L R 400w
> Tube(s) - R 200w
> Tube(s) L - 250w
> Tube(s) R - 170w
> Tube(s) - L 270w
>
> I also put a tuner between the rig and
> the amp. SWR was 1.5:1 but when i enabled
> the tuner i was able to get a little
> more power...
>
> 20m: plate current = 325 mA, HV=1900.. so P=617.5
> and with 50% effeciency that would be ~309w. I
> am seeing just under 400w so is the effeciency of
> this amp higher? 350w no tuner, 390 with tuner.
>
> 40m: plate current = 320mA HV=1900.. so P=608
> or 304 watts (@ 50%). I'm seeing: 375 w (no
> tuner) and 410 with tuner.
>
> Could the tubes be "OK" but "going bad" or do
> you see an indication of something else here?
> For 1200w input (600w output) shouldn't i be
> seeing 600+ mA? (1200w/1900 HV = 631mA). I'm
> seeing only around 320 to 325 mA when running
> with both tubes, and its my understanding that
> the meter should show the total current not
> per tube. Right?
>
> One thing i notice is that any single tube,
> when it is in the right socket, puts out
> more power than when it is in the left socket.
>
> Thanks for any comments...
>
> Steve, N9OH
>
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