[Amps] SB220 plate meter question

[Jim W7RY]

With the amplifier un-plugged.... Hook a small variable power supply across 
R1. Adjust it for mid scale. See if the current slowly goes down. Then you 
can troubleshoot it without high voltage.

Observe polarity.

73
Jim W7RY


-----Original Message----- 
From: gudguyham--- via Amps
Sent: Tuesday, November 07, 2017 4:50 AM
To: warren at warrenvolz.com ; amps at contesting.com
Subject: Re: [Amps] SB220 plate meter question

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 at warrenvolz.com>
To: Amps <amps at 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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