The AM Forum

Trying to resurrect an SB-200 that is part of my friend's estate. It was partially disassembled and missing one of the two 572 B's My question is, will the SB-200 run with only one 572B? Once I know it works, I'll get another tube.

I don't know, but if you have a spare 811a, you could try it....

klc

Running with one tube will screw up input and output impedance. I wouldn't recommended it. There's lots of things you can do to check its possible performance.
Visual inspection- things hanging loose, bad solder connections, part discoloration or just plain burnt.
Power Supply - depending on when it was built,  electrolytic capacitors are probably at least 40 to 50  plus years old. Likewise some of the other electrolytic capacitors and resistors should also be checked.
Check and clean the relay.
Check the DC voltages; don't need any tubes for that.
If all this stuff looks reasonable, spend the bucks and get two new tubes.

Or, just dump it on the market as is!

I have two SB-200's thst I've used since the beginning of time. They even work great on AM if you drive it with a piss weak exciter. ON SSB, my TS-830S works great with them.
Keying is important; the SB-200 uses -130 volts for keying so you can't use the typical solid state rig to key the SB-200 directly. Go to Harbach Electronics and get a soft-keying interface. They also sell power supply upgrade kits.

Yup, all good advice. We found this in a storage shed so it had several generations of spider webs. Disassembled, but all the parts were in baggies. I think it’s worth the work to get it back on the air so his wife can get the $$.
Thanks for the encouragement