I have an SB-220 that developed a high resistance between the tube socket
and the filament pins. I would pull the dark tube, inspect the filament
pins to make sure they haven't overheated to the extent that the solder has
dripped out. If so, re-solder. Measure continuity between the filament
pins. Polish the filament pins and socket filament contacts the best you
can with contact cleaner and Q-Tips. Reinstall the tubes, swapping
positions, and see what happens. When you reinstall the tubes, push them in
and out a few times to further polish the contacts. In my SB-220, that is
all that it took to get it going again.
If the filament is dark, there is no need for further testing with RF until
you solve that problem.
Dave Hachadorian, K6LL
Big Bear Lake, CA
-----Original Message-----
From: Ted Rachwal
Sent: Thursday, June 27, 2019 8:46 AM
To: amps@contesting.com
Subject: [Amps] Henry 2K desktop amp
All of a sudden I have a very high swr between the rig and amp...3:1....
I notice one of the 3500Z tubes is not lit. I'm wondering if I can pull
the unlit 3-500Z and try the amp to see if the issue is the tube or some
other part. I have pulled a suspect 572b and 811 in the Ameritron
series of amp and all was ok but wonder if the remaining 3-500Z would be
damaged if I tried this trick? Anyone have a thought here?
73,
Ted K8AQM
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