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I have a Tek 2235 o scope with a 1 1/2” vertical solid and fixed y-axis amplitude display that appears on both channels. Changing gain has no effect on the display, neither does changing the focus. Sweep timing is good. CRT display is bright. Using a 500 mV 1kHz square wave at the input does not have any effect on the screen display problem. Referencing the Tek service manual, I cannot find anything on the board amiss using another external oscilloscope to checkwaveforms. What is interesting is that the output signals leading to the upper and lower vertical control plates of the CRT appear clean and undistorted showing the 1kHz square wave, so the the problem must be in the CRT, or the associated circuitry. Has anyone seen this problem or know someone who does? I don’t know how to upload a photo quite yet, but I will figure it out soon.

Try cleaning the beamfinder switch with alcohol, exercise it 10-20 times after that.

Beamfinder is working properly. When pressed, the display compresses to a single position on the x-axis, but the amplitude remains. Here is a helpful hint...I pulled (disconnected) the upper and lower plate deflector wires from the CRT and turned the unit on again... without any vertical input connected, the CRT display was exactly the same as before...just a big rectangle-appearing image at all sweep speeds. This tells me that something is amiss in the CRT or associated electronics. Still scratching my head on this one.

Phil

Put the scope in X-Y mode, with no input signal, and
measure each vertical deflection output to ground.

They should be about the same voltage. If one is at
zero, or the supply voltage, that driver is burned out.

A very common problem that often comes from shorting
one output to ground.

-Chuck Harris

Pmccandless via Groups.Io wrote: