Bob:
Yeah, leave the line cord unlugged.
Measure the cathode resistor cold. It should be a few ohms. Plate current
times that resistance is a voltage drop. Assuming it is 3 ohms, 500 ma of
plate current wll be 1.5V. Try connecting a 1.5V battery prior (and check it
with a DMM while adjusting) to the pot and then adjust the meter for 500 ma.
You're done.
73, Steve K0SF
----- Original Message -----
From: w5pvr@triton.net
To: amps@contesting.com
Sent: Monday, July 16, 2007 11:23:28 AM (GMT-0600) America/Chicago
Subject: [Amps] Alpha 76 Plate Meter Calibration
The Plate Meter on this restored two tube Alpha 76 needs recalibration. The
circuit uses the cathode voltage drop across a resistor measured by the
Plate Meter. The meter is converted to a volt meter by a series variable
resistor (pot.). it has a d'Arsonval 0-1ma basic movement If I knew the
resistance of the meter I could set it using Ohm's Law. Should be between 50
and 100 ohm's. I could do this hot but I shake real bad and I don't want to
get toasted. Any help out there?.
Bob
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|