Re: tek 475 vertical position pots


pe1fbo@...
 

--- In TekScopes@y..., Emanuele Girlando <emanuele_girlando@y...>
wrote:
Vertical position pots on my tek475 are so noisy to make my scope
almost unusable.
Any suggestion on refurbishing those pots?
They are two sections pots, can I try to use the unused section?
Any source for them?
Thank a lot !
ciao

=====

Emanuele Girlando (IW1DHI)

http://space.tin.it/clubnet/egirland


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Hi Emanuele,

Those pots are probable Allen Bradly, and and have a double section.
There are two type of AB pots, The plastic sealed ones, and the ones
which you can nicely open with four screws. To clean the pot, you
have to take it apart (first remove them carefully from the Vertical
amp board). Once you have opened them you need to cut the plastic
seal inside the black plasic section to get to the brown whiper
section.

If you have everything apart, remove all the old grease and clean all
sections with alcohol. Mind you that the whiper has a tiny carbon
pallet, which comes loose very easy.

Once this is done you need to re-apply new grease. I use for this
purpose lithium based grease from Dow Corning, Molycote DX. Other
types of grease I cannot recomend to use. This is probably the same
stuff that Bourns uses.

After this, everything has to be assembled again.

There is one small remark on this whole procedure, that is, if the
carbon conductive film is worn out, the result will probably
disapoint you.

I have personally used this procedure on a lot of AB pots. They are
the ones usuly having problems due to the aging of the grease. And
can be restored most of the time with a good result.


- Fred de Vries

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