[R-390] Cleaning Potentiometers

[Leigh Sedgwick]

Just a single comment on a single potentiometer on the R390A (and other old 
BA receivers).  Chuck Rippel recommends replacing the S-meter zero pot on 
the IF deck with a new, ten turn, precision potentiometer of the same value. 
So I gave it a try, then quickly ordered 2 more, one for my 51J4 (which is 
installed), and one for my 51S1 which I am holding in spare for the day it 
starts to give me trouble.  Bottom line, set your carrier meter (easily) and 
forget it....it does not change every time you turn on the radio.  Ya, its 
not original, but, I kept the old ones and the improvement is well worth the 
trouble.

73 de Mike
K7PI


----- Original Message ----- 
From: "Tim Shoppa" <shoppa_r390a at trailing-edge.com>
To: <r-390 at mailman.qth.net>; <huffb at avalon.net>
Sent: Sunday, July 10, 2005 4:55 AM
Subject: Re: [R-390] Cleaning Potentiometers


>> What are you guys using to clean and take the noise out of carbon
>> potentiometers?
>
> A new pot.
>
> Off the top of my head, there are only 5 pots in my R-390A (local
> audio, line audio, limiter, carrier meter, if gain) and they're
> all vanilla.  (OK, the limiter has a little-bit-funky switch on
> the back, but if that's in fine condition, it can be transplanted
> to a new pot maybe with a little drilling/milling).
>
> When I do put new ones in, it's mil-spec cermet or plastic.  I'm
> not going to claim that they'll never get noisy, but they've been
> damn good so far.
>
> Tim.
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