开云体育

Hi all!

I am in need of a new "focus" pot for my Tektronix 475 scope, serial number B278849. The part Identifier is R1380. The Tek part number is 311-0075-00. Description is: Res., VAR, NONWIR:
5M Ohm 20% It is a small all metal round pot with a 1/4" bushing an an 1/8" shaft. The pot works electrically but is binding/stuck mechanically. It can be rotated, but it is very, very stiff. I'm afraid of breaking the fiberglass extension rod.
Tek, of course doesn't have it, and though it is a simple pot with no special push-pull switching, etc. 5 MegOhm is not that common a value any more so I have not yet found a quality generic replacement. I assume that this pot has linear taper.

Thanks for helping.

Steve Hogan
Can someone out there he

Lubricate the shaft where it enters the body of the pot with contact
cleaner. Turn the pot. Repeat
as necessary.
You will probably find it only takes one or two tries to get enough
penetration to fix the problem.
It is nearly 100% certain that this is all it needs to free it up. I
have never run into a case where this kind of mechanical binding
requires component replacement
Arthur Shulman

Steve Hogan wrote:

Hi all!

I am in need of a new "focus" pot for my Tektronix 475 scope, serial
number B278849. The part Identifier is R1380. The Tek part number is
311-0075-00. Description is: Res., VAR, NONWIR:
5M Ohm 20% It is a small all metal round pot with a 1/4" bushing an
an 1/8" shaft. The pot works electrically but is binding/stuck
mechanically. It can be rotated, but it is very, very stiff. I'm
afraid of breaking the fiberglass extension rod.
Tek, of course doesn't have it, and though it is a simple pot with no
special push-pull switching, etc. 5 MegOhm is not that common a value
any more so I have not yet found a quality generic replacement. I
assume that this pot has linear taper.

Thanks for helping.

Steve Hogan
Can someone out there he





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Service.

A renewed search of my Digikey catalog has part number 381N505-ND. ($13.35). This is a Clarostat 1 Watt conductive plastic linear pot with identical mechanicals to the original, which was also a Clarostat part. I was nervous about the 350 Volt rating, but if my calculations are correct, there is about 326 Volts across that pot in circuit, so it should be fine. Comments welcome.


I am in need of a new "focus" pot for my Tektronix 475 scope, serial number B278849. The part Identifier is R1380. The Tek part number is 311-0075-00. Description is: Res., VAR, NONWIR:
5M Ohm 20% It is a small all metal round pot with a 1/4" bushing an an 1/8" shaft. The pot works electrically but is binding/stuck mechanically. It can be rotated, but it is very, very stiff. I'm afraid of breaking the fiberglass extension rod.

Hi all!

1/2 drop of lubricant on the shaft instantly solved the problem. Pot turns perfectly now --like new. Thanks to each of you who suggested less drastic measures than replacement.

Steve