The Drake L4 uses a small resistor (I recall it is .82 rather than the state
.082 ohm) in the plate lead of the final tubes. It is my opinion that such
a resistor is a bad idea. Eimac mentions that surge resistor is appropriate
in the plate - but they want it large enough so that it will handle the
surge without failure. I am thinking something like 20 ohm at 50 watts.
The problem with that particular 2 watt resistor is:
1. When it "blows" it could easily arc across and therfore not act as a
fuse.
2. If it does blow, without any other circuit protection, the consequence
is that the operator will drive the grids with 100 watts and no plate
voltage, and the grids tubes will be destroyed because of excess power being
dissipated by the grids.
In all the Drake amps I have worked on, I have removed the .82 ohm resistor
and replaced with the Eimac recommended surge resistor.
Happy Thanksgiving, K7FM
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