Warren, well it could be a bad solder joint. The SB-220 plate meter has a PLUS
red wire and a MINUS black wire coming off the meter going to the rectifier
board. You must check the solder joints at the meter side and at the board
side. Then you have a 3600 ohm resistor as a series resistor for the plate
meter reading on the board, that resistor could have an issue or the solder
joints associated with that resistor and also the 1 ohm shunt resistor as well,
that needs to be looked at as well as solder joints on that. That is the
metering circuit in a nut shell. Unless there is some problem with the meter
itself you should find your problem in that area. Do you have a stock Heathkit
meter board or some aftermarket one? Lou
-----Original Message-----
From: Warren Volz <warren@warrenvolz.com>
To: Amps <amps@contesting.com>
Sent: Tue, Nov 7, 2017 3:41 am
Subject: [Amps] SB220 plate meter question
All,
My SB-220 is sick again. The plate meter works fine after start up but
then ~15-20 minutes later it starts to show lower and lower values.
Eventually it doesn't show any plate current, but the amp still produces
full output. It doesn't look like I have loose connections. I suppose it
could be a poor solder joint? Anyone have any other ideas?
-Warren KD5YPH
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