[R-390] Plastic Potentiometers and Magic Dust

[Cecil Acuff]

Be aware of companies formulation changes.  Example:

I have used Blue Shower for years for cleaning switch contacts, pots 
etc...in the stereo business...all the way back into the early 70's.

Sometime around 5 years ago Blue Shower was reformulated.  The can looked 
identical and had no indications on it that anything had changed.  A friend 
asked me to clean up the scratchy pots in a Pioneer stereo for him.  Which I 
gladly took on...

Shot the first one with Blue Shower and for the first few rotations all 
appeared to be fine then the pot self destructed.  A post mortem showed the 
plastic parts had basically melted down.

Reading the label on the can it did indicate that it was not safe on some 
plastics...that was new.  I had been using Blue Shower for years...decades 
with no problems on the same vintage gear with no problems.  A talk with the 
electronics store where I bought the product indicated that they had in fact 
reformulated the product to make it more environmentally friendly and now it 
was not safe to use on some plastics.

Last time I will purchase that....

So to make a long story short be careful what you use and where...and just 
because you might have used it for years doesn't mean it is still the same 
product you though it was....

Did find a suitable replacement pot and got the stereo back functional but 
was sweating it for a while...

Cecil
K5DL
----- Original Message ----- 
From: "Tisha Hayes" <tisha.hayes at gmail.com>
To: <r-390 at mailman.qth.net>
Sent: Sunday, March 20, 2011 11:16 AM
Subject: [R-390] Plastic Potentiometers and Magic Dust


> Those cheap plastic volume controls and the magic dust that makes up the
> variable resistance are indeed a big problem. The little wiper arm inside 
> of
> the pot eventually picks up a speck of dirt and begins to wear a track.
>
> I have not had much luck in really restoring their operation. You can make
> things better for a while but the only real solution is to replace the 
> pot,
> preferably with something that is not magic dust glued on a piece of
> plastic.
>
> The fader lube does work. I have a old clock-radio that has some personal
> significance to me that I at least got back to the point where the audio
> would not drop out completely when changing the volume.
>
> -- 
> Ms. Tisha Hayes/ AA4HA
> -
> Optimist: *The glass is half full.*
> Pessimist: *The glass is half empty.*
> Engineer: *The glass is not sized correctly AND we need a backup system.*
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