On Sat, 04 May 2019 11:52:56 -0700, you wrote:
OK Harvey,Ok. This is good. I'm not the expert here, but....
the H and V amplifiers work, the readout circuitry works. Assuming
that focus and astigmatism aren't related directly to intensity (I
don't know the circuit, so I can't tell). then the problem is mostly
Now this next is a guess....
Looking at how the test point is stuck at 120 volts, then I'm
suspecting that there is a transistor that has to pull things down to
blank. If so, then this transistor is normally on (blanked) and you
unblank the CRT by turning off the transistor.
Even if that isn't true, I'd look at the circuitry feeding that test
point. Don't have the schematics myself, but I'm sure others do.
Looking at the test point, is it pulled up by a transistor, or pulled
Which direction turns on the CRT?
The description of how the Z axis board works ought to tell you a lot.
Reading that ought to show you what waveforms are needed to blank the
display. You need (with another scope, and be careful, since I
*don't* know what voltages are on that board) to look and see if there
are unblanking pulses (go for an H sweep plugin, put it on auto
You should see pulses somewhere to unblank the scope at roughly 50 to
100 Hz. If you want them line locked at whatever your line frequency
is, then set the trigger to line and adjust the trigger voltage until
the triggered light is on. You'll likely see a line on the scope
Now see if those unblanking pulses are getting where they need to be.
What I'd do....