The other thing common to both channels is the block labeled "Mode Control Logic / Vertical Select / Trigger Select" - I'm not 100% sure what these do, but the problem could lie there as well. This seems like an electronics problem, not a CRT problem. There's two obvious things common to both CHA and CHB, all coupling - the CRT itself and the vertical amplifier (the "Output" triangle below). Here's the block diagram from the service manual.
That helps because it eliminates a bunch of blocks from the 'suspect' list. So whatever the problem is, it's common to both channels and all the coupling. Third, when you set Channel B coupling to AC and adjust the position knob, what happens? What about when you set coupling to DC? Second, when you set Channel A coupling to AC and adjust the position knob, what happens? What about when you set coupling to DC?
I am kind of winging it here.įirst off, does this behavior only happen on channel A? Or does this also happen on channel B? Let's see if we can isolate down to the block, circuit and then component levels. In the PDF take a look at the chapter called "Troubleshooting the Vertical Section" So maybe that has something to do with it. The vertical position adjust is part of the vertical section circuitry. You seem to be having a problem getting the beam to show up below a certain point on the screen. It also is responsible for triggering when to sweep, blanking the beam when sweeping right to left to start another sweep. The horizontal section is what sweeps the beam from left to right. At present I'd put my money on a problem with the vertical section. The vertical section controls the position of the beam on the vertical axis.
The power supply of course provides various voltage to all the other sections. The o-scope is made up of several main sections. So, step one, diagnose the faulty section. Their approach is-diagnose from the front panel. Take a look at that PDF and just kind of skim through it and get the gist. I couldn't make out the settings but that is ok.
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