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Re: [Amps] SB220 plate meter question

Subject: Re: [Amps] SB220 plate meter question
From: Warren Volz <>
Date: Wed, 21 Nov 2018 00:51:58 -0700
List-post: <>

I realized I never followed up with you on your reply. So a year later here is 
the result of my investigation.

The red “+” wire for the plate meter had some melted insulation and while I 
don’t think that was causing the issue, I replaced that wire just in case. 
After that I cleaned and retightened the contacts for the meter including 
replacement of the dried up rubber washers against the back side of the meter. 
So far everything is good. As you can imagine the metering board resistors all 
checked out ok.

The only negative outcome was I accidentally bumped the meter movement while 
cleaning and I believe may have bent the indicator slightly. It’s still close 
enough but some day I’ll have to try straightening it.

Thanks as always for your help!

-Warren KD5YPH

> On Nov 7, 2017, at 3:50 AM, wrote:
> 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 <>
> To: Amps <>
> 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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