[drakelist] T-4XB apparent vs actual plate current

[W5EI]

Hello again

Garey, as mentioned earlier, I had the bias pot on the AC-4 set for 70 mA on the xmtr meter.   Measured from the feedthrough terminal at the RFC connecting the cathode resistors to the wire from the 3.3 ohm resistor.  The initial reading was 67.9 mA.  I tweaked the bias pot a little bit, and got it as close as I could to 70 mA.  Then, after turning off the power, I turned the T-4XB upright, powered back up, and checked the idling current on the xmtr meter.  It's about as close to 70 mA  as I think I can get it.  It looks like changing out the meter shunt resistor has helped out quite a bit, and for now, at least, the 150 ohm resistor at the slide switch is OK.  Also tried Al's method to calculate for the current, and got similiar results.  I really need to invest in a Fluke  meter with some clip-on leads I can change out from the regular probe tips.  Using what I have around this type of voltage is asking for trouble. : - ) !

73,

Don
W5EI
Troup, TX