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[VHFcontesting] 3cx800a7 144 amp. April 84 QST

To: <vhfcontesting@contesting.com>
Subject: [VHFcontesting] 3cx800a7 144 amp. April 84 QST
From: John Allen via VHFcontesting <vhfcontesting@contesting.com>
Reply-to: John Allen <n0ja54@yahoo.com>
Date: Sat, 1 Apr 2017 19:21:30 +0000 (UTC)
List-post: <vhfcontesting@contesting.com">mailto:vhfcontesting@contesting.com>
Paul K0DOK has built the 3cx800a7 amp. using aluminum in place of brass for the 
plate line, and is not able to get the amp. to work.  He has 2000 volts on the 
plate, correct filament voltage, and a bias of about 5.1 volts on the cathode.  
The input tunes up according to the article description, resting plate current 
is about 50 ma.   When tuned for a dip in plate current the grid current rises 
higher than normal, and the plate current dips to a very low value.  Output is 
about the same as drive power.  We cannot see anything wrong with the circuit 
visually.  The plate circuit is tuned for resonance at the low end of the band. 
 It looks to me like the amp is to lightly loaded?   Any one with experience 
with this amp, or using the 3cx800a7 on two meters have any ideas or 
suggestions?   Could we have a bad tube?  HELP!
John, N0JA
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