Center the vertical positioning control with the sensitivity at 1 volt/cm or greater (minimizes signal pickup).
ground vertical input.
at the vertical deflection plates, measure the voltages.? They should be equal.
vary the vertical centering to see if you can get the voltages on each plate to match.? At that point, the trace is centered.? If you can't do this, then the trace won't center.
You can either start from the end or the beginning.
Looking at the schematic, there's one input to the vertical amplifier, which goes through a differential pair.? This produces a positive going and a negative going signal.? Each stage should have the same DC voltage with any signal being of opposite phase. If one signal through the amplifier chain doesn't match, then investigate that stage.? Transistors can be swapped from plus to minus to enable checking bad transistors.
There should be a very good section on how the amplifier works in the manual.? You'll find that the horizontal and vertical amplifiers are quite similar.
One possibility, given that the beam finder switch forces the beam to be on screen by reducing amplifier gain, is that you check around that switch for possible bad contacts.
Harvey
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On 12/23/2024 12:42 PM, Jeffrey Wang via groups.io wrote:
I shot another video to demo the current situation:
How do I troubleshoot the vertical amplifier board?
