SB220 Question - no plate current

[Jim Mullen]

Solved!

It appears it was nothing more than dirty contacts on the T/R relay. Guess
that's what I should have expected with something this old. The T/R relay
was one of the few parts I never changed.

Tubes seem to be OK. I'm seeing around 800 to 1000 watts into a dummy load
(CW position) on all bands, dropping to around 700 at 10 meters. I'm not
terribly familiar with these amps. It seems I need to drive the tubes too
hard to get the rated output. At that point the grid current is climbing
above the max (200 mils). I'm guessing the tubes are not quite as good as
they could be? Still not bad for a 20+ year old amp.

Thanks to all for your help and suggestions. See you on the bands.

Jim, KK1W

-----Original Message-----
From: Jim Mullen [mailto:jmullen at rockys.com]
Sent: Friday, April 16, 2004 11:32 PM
To: 'wb8jkr at JUNO.COM'; 'HEATH at LISTSERV.TEMPE.GOV'
Subject: RE: SB220 Question - no plate current


Solved!

It appears it was nothing more than dirty contacts on the T/R relay. Guess
that's what I should have expected with something this old. The T/R relay
was one of the few parts I never changed.

Tubes seem to be OK. I'm seeing around 800 to 1000 watts into a dummy load
(CW position) on all bands, dropping to around 700 at 10 meters. I'm not
terribly familiar with these amps. It seems I need to drive the tubes too
hard to get the rated output. At that point the grid current is climbing
above the max (200 mils). I'm guessing the tubes are not quite as good as
they could be? Still not bad for a 20+ year old amp.

Thanks to all for your help and suggestions. See you on the bands.

Jim, KK1W

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