Tektronics 2252 Scope

[specba]

I purchased a used Tektronic 2252 4 input oscilloscope. It powers up and the beamfinder shows a trace. The trigger led comes on when I feed it a video signal, but the only other trace I get is random noise. I do see a change when I change the timing. I have no operator or service manual. Any ideas where to start?

Thanks.

 

[cj_elec_tech]

Try the brightness cct (if the sweep is too dull, you can't see it) - the beamfinder overrides this and sets the brightness to (virtually) maximum,
or
try the Vertical Deflection Offset voltage (the sweep could be above or below the CRT phosphor area - the beamfinder reduces the overall vertical deflection voltage to ensure the sweep hits the screen phosphor

or maybe I'm not diagnosing your description properly: could you take some photos of the screen and post them so we can see what you are trying to describe?
Hope this helps, please let us know how you go.

CJ

 

[neon]

i feel sorry for you without a manual how do you expect to ever calibrate this sucker or you think it will stay status quo foreber.I am afraid you have bought someone else problem.

 

[specba]

More information

I purchased the full service and operators manuals on disk. The circuit does a feedback loop so it's difficult to diagnose. The problem seems to be in the vertical amp area. I do get a trace in calibration mode.

I'll take a picture of the CRT and post it.

My experience has been that if I have a problem there might be someone out there who has seen the same problem and has solved it. It can save hours or even days of chasing my tail and head scratching.

I'm a teacher and want to use the scope to show waveforms to my students as part of a computer repair class. Calibration is not as critical because I don't plan on using the scope for alignment or repair.

Thanks.

 

[shrtrnd]

My two cents, which may not help. Last two 2252's I worked-on, the problem was in the top row of pushbuttons (Clear Display thru Store/Recall set-up). You may very well have a circuit problem, but I'd take a serious look at those push-buttons (the switches themselves), before I knocked myself out on the circuitry.
Good Luck