tek 475 vertical position pots


Emanuele Girlando
 

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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Michael Dunn <mdunn@...>
 

At 3:56 PM -0800 2001/3/24, Emanuele Girlando wrote:
Vertical position pots on my tek475 are so noisy to make my scope
almost unusable.
Any suggestion on refurbishing those pots?

Surely any owner of "classic" equipment should have a can of good contact cleaner always at hand!!! :-) Perhaps even WD40 would work??? If the pot is just supplying a DC voltage, I guess you could always hang a big capacitor on the wiper!? Have you tried simply rotating the pot back and forth a few dozen times? This often helps, at least a bit.

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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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Get email at your own domain with Yahoo! Mail.
http://personal.mail.yahoo.com/
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


Emanuele Girlando
 

I confirm: "the pots are Allen Bradly, and have a double section";
one section seems unused (not connected).
I confirm: they are "the ones which you can nicely open with four
screws".
So your tips are very very useful.
For the sake of completeness and want to say that I have already
tryed to turn them back and forth a lot of times but with almost no
result.
Furtheremore it is impossible to squirt any form of conctact cleaner
without opening them.
Thank you very much for your contribution, I'll keep the list updated
on my activity.
ciao



--- In TekScopes@y..., pe1fbo@h... wrote:
--- 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


__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.
http://personal.mail.yahoo.com/
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


Emanuele Girlando
 

An update.
I spent two hours in dismounting the vboard and un removing the pots
from it. What a nightmare! If any other people is about to start an
adventure like this, please be sure to have a perfect and efficient
unsoldering machine. I spent a lot of time trying to get rid of the
tin that was keeping the pots on the board. My solder sucking tool
was insufficient. I used a thin plaited wire to get the tin out of
the PCB holes by capillarity.
The pots are now in my hands and I am going to work on them the next
weekend (hopefully).
until next time
ciao

--- In TekScopes@y..., "Emanuele Girlando" <emanuele_girlando@y...>
wrote:
I confirm: "the pots are Allen Bradly, and have a double section";
one section seems unused (not connected).
I confirm: they are "the ones which you can nicely open with four
screws".
So your tips are very very useful.
For the sake of completeness and want to say that I have already
tryed to turn them back and forth a lot of times but with almost no
result.
Furtheremore it is impossible to squirt any form of conctact
cleaner
without opening them.
Thank you very much for your contribution, I'll keep the list
updated
on my activity.
ciao



--- In TekScopes@y..., pe1fbo@h... wrote:
--- 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


__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.
http://personal.mail.yahoo.com/
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