SB-221 Question

[Wallace Gibbons]

Greetings,

How can one tell if the tubes are fried in this beast? Idling current on
CW/TUNE is approx 100ma, 150ma on SSB. That appears to be normal. But
output power seems down and plate tuning is off from the band segments
on the panel versus plate current dip. Loading always peaks at minimum
setting, on all bands.

I had to replace the .82 ohm grid current sense resistor. Original was
open. Looked fine, just open.

Tubes show red at idle on SSB, too.

Fixing this for a local ham, and don't have the experience with these
brute amps.

Any tips apprecaited.

I do have the construction manual, but schematic is missing.

Thanks.

Wally Gibbons
Rockwall at tcsourceone.com

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