[AMPS] Grid Current problem

[W7CW Jay E Ostrem]

Hello McFly, Are you in there?

After speaking with the fellow I bought the Simpson meters from, I found
only the plate meter was direct reading, the grid meter needed a shunt.
This cleared up the weird metering.Thanks for the hint Rich.

Another question,  When I set the resting plate current at approx 400mA,
the Grid current comes up to 25mA, at 600mA it comes up to 50mA, does this
mean anything?  Everything seems smooth.

The little fella tops out at 1300 watts with 3400v on the plate, 50 watts
drive, and is grid current limited at this point. Efficiency is poor.  I'm
not using a tuned input yet, still playing around.

To answer other questions;

All of my filters and the transformer are negative on PCB's

The YC156 has an oxide cathode. (med grade 3cpx5000)		

The cathode is common to one side of the filament. I have been told the the
ring is the common point.


>X-Sender: wc7m@vcn.com
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>Date: Sun, 06 Dec 1998 10:35:35 +0000
>To: amps@contesting.com
>From: W7CW Jay E Ostrem <wc7m@vcn.com>
>Subject: [AMPS] Grid Current problem
>Sender: owner-amps@contesting.com
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>
>
>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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>
>
                              73 Jay W7CW

                                 1AB Ranch
                                 Gillette, Wyoming

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