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[Amps] SB-220 no output

To: amps <>
Subject: [Amps] SB-220 no output
From: Warren Volz <>
Date: Tue, 25 Jul 2017 00:59:54 -0600
List-post: <>

I ran into another hurdle with the SB-220 and am hoping someone has some 
wisdom. If I run RF through the AMP without power applied the relative power 
meter works and I can match my dummy load without issue. Side note, is the 
relative power meter supposed to line up on the bottom scale with actual 
forward watts? Ie: 100 Watts = 100 on the multimeter scale? Once I enable my 
rigs “amp keying” mode and transmit with anything from tune mode to a carrier I 
see high SWR and 0 output after the amp.

To troubleshoot, I hooked up my DMM and triggered the keying interface so that 
the relay(s) engaged. I’ve confirmed that both are working correctly. Oddly if 
I put the DMM in continuity test mode and trigger the TX mode on the amp I get 
a beep. So, the RF is blocked someplace inside the tank circuit or band switch? 
That’s my best guess. Or is it possible that a bad tube would cause these 
symptoms? There is no deflection on the plate meter when I’ve put RF in. Does 
that mean the tube is being held in cutoff?

Thanks for the help again. It’s challenges like this where I wish I had a local 
elmer to help out!

-Warren KD5YPH
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