Tektronix 7623 sweep problem

Hello, I have recently acquired a Tektronix 7623 with 7B53A time base.
I've made several repairs on the unit and have it almost fully
functioning. The last major issue relates to the sweep speed and I'm
not sure how to describe the symptom or what could cause it. Any sweep
speed from 0.5ms/div and faster seems to work properly, but above that
my sweep range is cut in half for each increment. So 1ms/div only
displays on the left half of the crt, 2ms/div only displays in the
left most edge of the screen and so on. I have taken some (quite
blurry) pictures of the issue and posted them on http://bob.desinc.net/tek7623/
if anyone is able to give me advice I would greatly appreciate it. I
have the same issue with both vertical amps (which appear to be
functioning properly). Thanks -Bob

 

[Franc Zabkar]

On Thu, 14 May 2009 12:19:20 -0700 (PDT), desinc@gmail.com put finger
to keyboard and composed:

Hello, I have recently acquired a Tektronix 7623 with 7B53A time base.
I've made several repairs on the unit and have it almost fully
functioning. The last major issue relates to the sweep speed and I'm
not sure how to describe the symptom or what could cause it. Any sweep
speed from 0.5ms/div and faster seems to work properly, but above that
my sweep range is cut in half for each increment. So 1ms/div only
displays on the left half of the crt, 2ms/div only displays in the
left most edge of the screen and so on. I have taken some (quite
blurry) pictures of the issue and posted them on http://bob.desinc.net/tek7623/
if anyone is able to give me advice I would greatly appreciate it. I
have the same issue with both vertical amps (which appear to be
functioning properly). Thanks -Bob

Just a WAG, but could there be a DC offset in the time base amp before
the selector switch which is being amplified by the following stages?

- Franc Zabkar
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