N3VC's SB-200
before & during work
It was owned by a heavy smoker by the looks.
Done, with old tubes installed for checkout. I have done some cleaning,
but more will be done.
I installed Ken Simpson's suggested mods, back-to-back diodes on the meter,
and a diode across the antenna coil.
With my shack wattmeter, the old tubes (both OK) will get over 500w output on all bands, driven with approx. 100w from my Ten-Tec Omni V. (The wattmeter used is 500w f.s.)
the above pix are after mods, before cleaning, show heavy nicotine stains, and
it smells when hot.
compare with the ones below, should look cleaner. I only did light damp
cloth cleaning on the front panel, the paint & lettering will come off if
scrubbed.
I will install old, then new, tubes and put the "big" wattmeter on it to compare readings.
Here's what I'm getting for power readings:
Freq. Ip, ma. Pwr out, watts Load
ctrl setting
3780 500
740
3
7280
500
840
4
14280 500
900
5
21280 500
900
4-1/2
28280 400
450
5-1/2
Not very efficient on 10, that load setting gives the max. power out The
input ckt tuning has little, if any, effect on 15 & 10m. Input SWR is
about 2:1 on those bands, so it's not a mismatch.