[Amps] AL80B low power

art421 at cox.net art421 at cox.net
Thu Mar 14 20:54:12 EDT 2013


I was testing a used 3-500z and blew the swamping resistor in the filament ckt. I replaced this resistor and put my original tube back in the 
and it will only draw 300ma on the plate and 100ma on the grid. The grid resistor R28 in stby has +25V and goes down to 9.5V in xmit. I thought it 
should go to 0V.
I am trying to find out if the tube is gone or has something else gone kapoot. I replaced Q2 and Q3 on the SWR board.
The AMERTRON schematics leave to much hanging. I wonder if anyone has made a good schematic of the AL80B.
Any advice as to what might be wrong with the amp would be helpful.
Art W3TZ 


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