Cermet vs plastic pots..

[Eric at Svetlana Electron Devices]

>I've seen the Mouser ones last much longer than 5 years, even in smoky
>environments, but the worst and noisiest pots I've encountered in synth
>restores- Emu modulars- Conductive plastic.
>They *should* be great. They look great on paper, they are wonderful when
>new, but they just don't seem to hold up.


Let me second some of Kevin's comments.

IMO, some sealed pots are a real problem. I have been using those Allen-Bradleys
for nearly 20 years, and they REALLY ANNOY ME. Invariably they start to
get noisy, and there's nothing you can do but replace them.
This happens regardless of the application: solid-state, tube, applied
voltages, dissipation, etc.....

I have tried drilling holes in them to spray in Caig D-5; it works, for
a while---then gets noisy again after it dries out. And, obviously, sometimes
metal shavings from the drilling get in and short out the element......

Had similar experiences with cond-plastic Spectrols and some cermets.
The blue-plastic-body ones are very flimsy and must be treated as such.
(Trimpots seem to be less prone to this than panel-mount pots.)

Cermets are necessary for special applications (such as low temp-drift
for VCOs), but longevity may be an issue.

The pots Paul is using are probably the best available, so if you
take care of the equipment, you can expect long life.

Some serious suggestions:

-Keep it clean, keep the dust off it.

-Don't overtorque the mounting nut. You will gain NOTHING by tightening
  it with a wrench until it squeaks. (I've seen it done many times by the
  overzealous types....)

-Don't overuse the pots--if something requires constant adjustment,
  it might pay to add a fine-adjustment pot, and replace it occasionally.
  (Or modify the circuit parameters....)

-Stay well within the rated power dissipation. Remember, many circuits
  can put a lot of current thru a pot at its minimum setting. Sometimes
  adding a 100-ohm resistor at the low end of the element
  can save the pot in the future.

Cheap pots, cleaned occasionally, seem to last a long time. Caig D-5 is
a magical elixir and is highly recommended. 

Take care of your equipment and it will outlive you.  Perform regular
maintenance, as if it was commercial equipment.

Bad pots tend to be on equipment that was/is owned by the stereotypical
lazy, constantly broke rock-n-roll musician......present company excepted,
one hopes.......