[Test-Equipment] Tektronix 2235 Wierd Problem/Question & Availability

[Robert Downs]

Last summer, I bought by accident a 2235, when what I really meant to buy
was a 2335.  Before I try to re-home the 2235, I need to mention the one
problem it has (I didn't have a chance to do anything more than turn it on
and confirm that it had a trace when I bought it).

When I got it home and installed it above the work bench, I discovered that
when I connected it to the audio sig gen, the horizontal channel/sweep,
trigger, intensity, etc. all worked as expected.  However, the vertical has
a problem that I can't offhand even think of a way to make it do.  About the
left 60% and the right 20% of the display looks fine.  But between about 60
and 80 percent across, it looks like the vertical sensitivity is modulated
or decreased by one cycle of a rather low frequency sine wave.  Weird
looking.  It starts off with no effect, the vertical amplitude decreases
symmetrically to about 20% and then it goes back up to where it was.  It
stays in sync with the triggered sweep and doesn't move if I change the
sweep rate.  

Has anyone ever seen anything like this?  Everything else about the scope
looks or works fine.  But no one would want to have to use it with it
misbehaving like this.  I'm not really interested it fixing it and intend to
offer it as a parts set but wanted to make sure that that no one can think
of anything wrong with the CRT itself that could cause this.  The scope is
in Houston.  If it were a 2335, I'd use it for parts to fix my original 2335
(no trace).  

Robert Downs