Got a Tek 454A the other day and did a quick test. It turns out that the only way to see a trace on the screen is to hold down the “Beam Finder” switch. As soon as it was released, the trace was gone. I shot a video to demo the problem:
https://youtu.be/7HERqOtBGOo?si=wpvnHFCTCqLt0IzT
Thoughts?
Most of the waveform is off the screen as you have the vertical sensitivity turned up too high. With a 1Vpp calibrator signal fed into a 20mV/div vertical setting you need 50 divisions to display the tops and bottoms of the waveform.
Turn the vertical range to .2V/div or higher so you can see the whole waveform on the screen. Or use a x10 probe to connect to the calibrator signal - this will bring down the displayed amplitude to 5 divisions.
Also check the vertical offset is OK. Switch the inputs to GND and adjust the vertical position control to get the trace on the centre of the screen. Repeat for both CH1 and CH2 and for ALT and CHOP modes to verify no extraneous offsets are being added to the beam position.
Tried all vertical sensitivities and it didn’t make any changes. Also tried a x10 probe, still nothing. Switched trigger to GND, nothing. When you mention vertical offset, did you mean the “position” knob? Tried that as well, nothing - in beam finder mode, it moved the line up and down so the knob works fine.
I’m curious, why in beam finder mode, the waveform and the trace were clearly visible - it’s just that the screen was vertically compresses, which I suppose it normal. That said, everything disappeared as soon as I let go off the momentary switch. What exactly did the beam finder switch do? I’m assuming it does not only increase the cathode voltage, but also something else, right?