Howdy,
I currently own two SB220s, one of which I bought in 1982. When I
purchased it, it had a standy switch, step start in the power supply,
filament step start, and an open .82 ohm resistor. My repairs
consisted of removing all the step start garbage, replacing the
resistor , removing the 200 pf caps and rf chokes from the grids and
directly grounding them, and getting rid of the standby switch ( I
even filled the hole in the front panal and touched up the paint).
Four or five years later the fan got noisy so I replaced it with a
220 VAC fan that fills the cut-out for the fan and installed a 24 VAC
transformer as an auto transformer to knock the 220 down to around 180
VAC.
The result is a fan that is quieter than the original while pushing
more
air.
Now, after 15 years of operation it is on my workbench with the
covers off so I can repair the on/off switch...it has been turned on
and off so many times the switch finally gave up. I plan to use the
cw/tune - ssb switch as a replacement...it has not been moved from the
high
voltage position since the day I started using the amp. Guess I can
fill that
hole up too.
Since the covers are off, I cant help but see the diode board. All
those diodes
in a string bother me for some reason, and I do have some diode modules
from
"Siicon Alley".
73, Bob, W5AH
P.S. Measured RF output on 10 meters is still over 1000 watts with the
original
tubes...1200 on 80 meters.
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