[Amps] Triode grounded grid amp strange failure

[Dave Hachadorian]

This type of thing can happen if B- and ground are tied together. 
There should be a beefy diode between B- and ground.  Sometimes 
this diode can short if there is a high current glitch event. 
Also, the plate current meter may have blown open during such an 
event.

Dave Hachadorian, K6LL
Yuma, AZ




-----Original Message----- 
From: Guido Tedeschi
Sent: Tuesday, July 14, 2015 1:47 PM
To: amps at contesting.com
Subject: [Amps] Triode grounded grid amp strange failure

Hello All,
     a homebrewed two chassis 3CX3000A7 GG amp of a friend has 
this
strange failure when switched on TX:
- no more current on plate meter
- 200 mA of grid current with no signal
- some power out (few hundred Watts) when driven with 40-50 W, to 
limit
the grid current to less than 500 mA, but still no current on 
plate meter

We don't have any schematic diagram so, before opening the amp 
and
troubleshooting, some suggestions to begin would be very 
appreciated
(hoping that the tube will not be the culprit...).
Thanks and 73
Guido
K2BCP

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