My second problem was not
being able to set the DC Offset to zero. It sat at about a minimum of
230mV plus or minus 15mV regardless of the gas tubes I randomly swapped in
there. I tried half a dozen all up and decided that the issue was
elsewhere. What I did in the end was replace a 1k resistor that leads
into the 100k potentiometer for trimming DC on the positive side with a 100k
resistor, so 100 times larger. The offset now trims to zero with the pot
close to halfway through its travel. Romy, I don't know if that is an
error on the schematic or if I have some other issue, but the offset seems
stable. |
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