[sdiy] Cleaning old serge pots? (crossposted)

[Glen]

At 04:32 PM 6/22/03 , Peter Grenader wrote:
>If they are the blue sealed (ha!) AB (Allen Bradley's), the ONLY thing
>that's going to get rid of the noise is a pair of cutters and a nut driver -
>you're gonna have to replace them.  those were a nightmare.

I'm assuming that we are talking about the same AB hermetically-sealed
metal-bodied pots when I say this. I once thought they had to be replaced
also. I was told by the service rep from a manufacturer that those pots can
indeed be "broken" open.

I tried it myself. Take the pot out and pry the retaining tabs back with
something thin and flat (knife, screwdriver, wood chisel, etc). Then mount
the pot in a vise and separate the metal rear shell from the body of the
pot, using something like Channel-Lock (tm) pliers. It seems brutal, but it
works. 

Once the back is off, most of the pots I've tried actually did respond well
to cleaning. Of course some will be hopelessly worn out, but this is often
worth a try, especially if it prevents you from having to order parts and
wait on delivery.

When you're done, just put the shell back on the pot and bend the tabs back
into place. Don't worry about the gluing the shell back together.

Later, I experimented with cutting a slot in the back of the metal shell
with a Dremel(tm) tool. I would then spray a flood of contact cleaner into
the pot. This usually worked well also. It is quicker to do it this way,
but it is also trickier. If you slice too deeply into the pot, or at the
wrong place, you will ruin it. There is also the chance of a very small
amount of metal powder getting into the pot and causing some extra wear, or
at least I think this is a possibility. To be honest, most of the metal
that is ground away goes flying away as sparks during the grind process. 

Once you experiment on a few old pots and get used to the procedure, this
might be a viable technique, especially for non-mission-critical
potentiometers, or as a temporary measure until a new pot arrives in the mail.

Later, I can post a photo of the type of pots this works on, if there is
any doubt as to the model I am referring to.


later,
Glen Berry