I've run out of ideas and could use some suggestions that may help to rescue
this SB-220 of mine.
I had a catastrophic failure a while back due to Zener diode shorting that
set off a chain reaction on other components. I have since replaced the
meter/rectifier board with one from Harbach, did his parasitic mods and
replaced the two
3-500Z with new EIMACs. No matter what I do, the maximum power output that
I can get in the CW position is about 700-800 watts (500 watts on 10m), and
which is about 100 watts more than the old tubes. This is with 50-100 watts
drive (depending on the band). This output is achieved with a plate
current of about 350ma and a HV of 2100. Now if I do the math, something is
wrong. Also, I cannot seem to load to more than 350ma.
I've checked the meter/rectifier board and all components read OK. Plenty of
grid and yes the input swr is 1:1 on all but 10m where I have to use the
built-in antenna tuner on the exciter (FT-1000D).
I suspect that with 700-800 watts out that is about all one can expect and
that the plate current meter must have taken a hit and not reading
correctly.
Any suggestions or comments would be appreciated.
Walter - VE3EN
wfairclo@netcom.ca
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