[Amps] 2M 8877 Amplifier: No grid or plate current

[RICHARD GEORGE]

Sounds like no fils or the cut off bias is still up. Check to see if the fils are drawing current. I usually do this buy putting an ac voltmeter right at the fils and turn on from a cold start, you should see the filament voltage increase as the tube warms up. As for the bias, make sure the fuse if there is one, is good and that your PTT Relay is closing the resistor in series with the bias.
  ----- Original Message ----- 
  From: W.F van Wyk<mailto:zs6arf at telkomsa.net> 
  To: amps at contesting.com<mailto:amps at contesting.com> 
  Sent: Thursday, April 12, 2007 11:01 AM
  Subject: [Amps] 2M 8877 Amplifier: No grid or plate current


  Greetings,
   
  I am attempting to commission an 2 meter 8877 home built amplifier.
   
  As I did not do the construction I have to reverse engineer.
   
  The mechanical and electronic construction do look sound and according to
  the schematic I have with the amp.
   
  There is about 2,200 Volts on the anode and 4,7 Volts on the filaments.
   
  Problem is with or without drive I get to see not Grid or Plate current on
  the meter (which is functioning).
   
  Also I get to see the RF through but when I initiate the AMP the RF through
  decreases and no setting will get any response.
   
  Other than the tube being damaged what else can I look for to be the
  problem?
   
  Any tests I can do on the tube?
   
   
  73
   
  Wynand
   
  ZS6ARF
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