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I tried the Youtube guy's method and that's how it comes apart. You still have to figure out how to disconnect one cable.
That done, I was able to find out that the main low voltage seems to be OK.
The backlight seems to be fed a >100 volt AC power at some high voltage
for the couple of seconds when the display is visible and correct, then shuts down.
There is only one HV cap in the power supply, 160 uF at 450 volts. It seems
to have about 200 volts DC across it, with maybe 15 volts AC at 60 Hz.
There is also about 200 volts AC, roughly square wave at 60 (or 120, I forgot to check) Hz from it to ground.
So it looks like there is something wrong with the backlight, be it power
or a problem in the backlight itself that is causing a protection shutdown.
Any comments? Like ... is this effectively fatal? This display has given many years of faithful service.
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