[Dekatron]

Nice that you got it to work at the Cal. position!

Since it works in the Cal. position I'd check every soldering on the wires of the mA/V switch and the switch itself.

Also check R35 @ 2.4k, mounted at the back of the switch, I've seen several burnt out of that resistor. I've also seen unsoldered wires and dry joints on that switch too.