[Johnson] Desk Kilowatt meter

[Robert Nickels]

Has anyone experienced intermittent operation of the PA Grid/Modulator 
current meter in the Desk Kilowatt?

I first became convinced that it was a flaky toggle switch so I tore it 
all apart and carefully replaced it, with an identical NOS Arrow Hart 
switch I had on hand.  I checked it out using an adjustable current 
source with the grid temporarily grounded since there's no way to do so 
once it's all buttoned-up, and the meter worked perfectly and the 
accuracy was good.

But after proceeding with checkout of the amplifier I still am seeing 
very intermittent meter operation.  I've rigged up a temporary current 
measurement (by measuring the voltage drop across the appropriate bias 
resistor) so I know when the proper drive is being applied, but 
sometimes the grid meter shows zero, sometimes 20ma, and sometimes a 
value in between, often > 5ma.    Since the modulator plate current is 
also intermittent this means the problem lies in the new switch or 
wiring (both of which I think are unlikely) or the meter itself.    One 
difference is orientation, it was facing horizontally when I had it on 
the bench but of course is vertical in actual use.

The amplifier works fine in all cases with proper plate current, power 
output, and modulation, so this is strictly a metering issue.

I'd like it to be right, and if I go through the process of tearing it 
down again I sure would like to find and fix whatever is going on,  and 
if that involves removing the meter from its housing it would be good to 
know if others have been down that path.

Thanks and 73,

Bob W9RAN