bad precision pot?

[Martin Czech]

:::>So far I've never encountered any problems with cermet 10 turn
:::trimmers.  
:::<>But it is true that they are not made for many thousands
:::of revolutions, 
:::>the cermet film is said to suffer. They are made for
:::ocasional trimming.  
::: 
:::Well, the settability isn't always as good
:::as you might expect. You often have to turn quite a bit befor anything
:::happens. And if you turn too far and have to turn back, there is even more
:::"dead" travel befor the setting changes. I'm not sure if the setting
:::changes if you knock on them, but it could. Read Bob Pease's book and
:::see what he thinks about multiturn trimmers...

I always use these trimmers, almost never carbon types.  I have never
experienced exessive "dead gear", but I have never checked if they
change with vibration. This could be. But the usual carbon types have
wipers that also act like a spring, there is mechanical strain in order
to get contact, there is certainly a "dead travel" and maybe also change
with vibration.

I've to check this at home.

Maybe attach two measurement cables , read the value and then put the
trimmer in a box and shake as strong as I can, then read again.

m.c.