I have a homemade 8877 amplifier that covers 160, 80, 40, and 20 m and used
almost exclusively on cw. The power supply puts out a very stout 4000 vdc.
The grid overcurrent protection circuit is set to trip at 90 ma. I
normally adjust the drive from my Orion to produce a plate current of 400
ma, the grid current bring zero (that's right, no grid current showing on
the meter when the amp is properly loaded). The power output on the Orion
screen shows about 17 under these conditions. Question: Could I be
damaging the 8877 from overshoot? I have no way of measuring how quickly
the trip opens but am hoping that, with a grid dissipation rating of 20
watts and a trip setting of 90 ma, the thermal inertia of the grid will be
sufficient to prevent damage. The overcurrent circuit has never tripped
under normal operations.
I do believe that the grid circuit is behaving properly because I get plenty
of grid current if the amp is too lightly loaded, and a couple of times it
has tripped out when I forgot to set the output control on the Orion to
minimum before I started to tune up.
73 Paul W5DM
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