At 01:49 PM 09/11/1999 -0400, you wrote:
>
>
>I opened the grid return line above the bias switch (Q5) and inserted a VOM.
>When the VOM indicates 100 ma. of grid current, the panel meter reads 250
>ma. If I tune using the VOM indication for grid current the amp seems as I
>would expect. Makes about a KW on low power with about 50 watts of drive
>and 100 ma of grid current
>
>So I feel fairly comfortable that the panel meter is off by about 250%.
Hi Jack,
I took a look at the grid current measuring circuit in this Alpha 77DX and
inserted my Fluke 8050A multimeter and for 200 mA of grid current on the
amplifier meter the Fluke was measuring 60 mA with about 50 watts of drive.
So my circuit was 333% off. I changed R211 on the CB2 board from 1K to
3.3K. The exact resistor required is 3.333K so I measured a few I had in
the junk box and found one that was 3.328 K. Now the amplifier measures
about 63 mA and the Fluke 60 mA.
Close enough for me.
73 Hardy N7RT
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