[VHFcontesting] 3cx800a7 144 amp. April 84 QST

[John Allen]

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