I finally got my YC-156 on line, sort of. As noted in my earlier
transformer post, I am using about 3400Vdc B+, which effects my design RL
of 2400 ohms which the amp was designed for.
The following problem doesnt even require application of B+, and is
something I haven't seen before.
The amp design looks like any run of the mill 3-500Z cicuit, but is
physically 3X bigger.
When the filaments come up, the grid current meter pegs below zero.
When I short the bias cut off resistor the grid current goes way positive.
This is without excitation, or B+.
I am using a variable shunt regulator (two terminal device) in place of a
bias zener, and this is located directly below the filament transformer on
the other side of the chassis.
I can vary the bias from .6 to 30V, the grid current goes from 25mA to "oh
my god"
I have checked the filament circuit bypass caps (.01 disc ceramics) with an
ohm meter, and nother is shorted.
Nothing is shorted in the tube (all open).
I tore the covers off and checked my wiring of the metering circuits, all
appears OK.
The grid current indication is the same with the B+ attached or detached;
as is with the dummy load and input circuit.
What gives?
73 Jay W7CW
73 Jay W7CW
1AB Ranch
Gillette, Wyoming
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