[Test-Equipment] Red VAR control Re: Tektronix T935A Scope - seized knobs

[RJ Mattson]

Hi Roger,
The red knobs won't turn in either direction.
I loosened the red knob set screw and the red knob came right off.
The  inner v/div knob then just pops right out.
The red knob nylon shaft goes deep into the scope and still wont rotate in 
either direction.
I'll have to remove the case. Hope the problem will then be in view ?
Bob

----- Original Message ----- 
From: "Roger Shultz" <nj2r at verizon.net>


Hi Bob,

I read a couple other responses and I have a T-935 which is a wonderful
scope.

I was wondering it maybe the red knobs are not seized rather perhaps you may
have forgotten that they lock in the fully clockwise position and have to be
rotated counter clockwise to enter the variable range? I don't think they
are particularly intuitive in marking that.

In any event, I'd loosen the knobs to be sure they just are not pressed
against the outer range knob. If you have to open it up it is very easy and
you can then see the shaft arrangement. This is a simple yet wonderful scope
and if you are in NJ and I can help you please let me know.

73, Roger, NJ2R

-----Original Message-----
From: test-equipment-bounces at mailman.qth.net
[mailto:test-equipment-bounces at mailman.qth.net] On Behalf Of RJ Mattson
Sent: Wednesday, July 21, 2010 7:52 PM
To: Discussion of Electronic Test Equipment
Subject: [Test-Equipment] Tektronix T935A Scope - seized knobs

Tektronix T935A Scope.
The center red "VAR" knobs on both Chan A & B Volts/Div Amp. knobs have
seized.
In other words, either red knob won't turn at all.
What is the cure?
Do I have to open the cabinet to work in a penetrating oil on the shafts
from the inside?
Or,
Just remove the knobs and try to un- seize the shaft from the outside?
Or ?
bob...w2ami