Thanks for replying. It is odd. The monitor also has been tried on many machines, with the same result.
The monitor cable on these includes an ADB cable (the cable splits about a foot from the end into DB15 and ADB), and I have in the past been inclined to wonder whether the cable may be defective. However, there are two separate ADB plugs on the base of the monitor, and on connection of two ADB cables, one to the monitor from the keyboard and one from the monitor to the machine (in order, in theory, to by-pass the ADB cable that runs into the innards of the monitor), the same symptoms present. I assume that this means that something inside is awry.
Odder still is that, through it all, ADB peripherals such as Mouse, Wacom Drawing Pad, Kensington trackball etc. seem to work just fine. However, I have the AppleVision error, with attendant problems as described. I have also taken great pains to install proper System software; the trouble does not lie there.
Unfortunately, I am afraid to go in there to tinker, as not only does it look excessively complicated, but a) I have no schematics; and B) whereas ordinarily I might take the chance with soldering iron and take it on the chin if I got it wrong, I am in this case frankly afraid of the very considerable electrostatic potential stored in a 20" ColorSync. Electronics ignorance and one of these beasts do not make for safe play.
More modestly, is there some way of testing the various wires in the ADB connector with the monitor turned on?
The monitor cable on these includes an ADB cable (the cable splits about a foot from the end into DB15 and ADB), and I have in the past been inclined to wonder whether the cable may be defective. However, there are two separate ADB plugs on the base of the monitor, and on connection of two ADB cables, one to the monitor from the keyboard and one from the monitor to the machine (in order, in theory, to by-pass the ADB cable that runs into the innards of the monitor), the same symptoms present. I assume that this means that something inside is awry.
Odder still is that, through it all, ADB peripherals such as Mouse, Wacom Drawing Pad, Kensington trackball etc. seem to work just fine. However, I have the AppleVision error, with attendant problems as described. I have also taken great pains to install proper System software; the trouble does not lie there.
Unfortunately, I am afraid to go in there to tinker, as not only does it look excessively complicated, but a) I have no schematics; and B) whereas ordinarily I might take the chance with soldering iron and take it on the chin if I got it wrong, I am in this case frankly afraid of the very considerable electrostatic potential stored in a 20" ColorSync. Electronics ignorance and one of these beasts do not make for safe play.
More modestly, is there some way of testing the various wires in the ADB connector with the monitor turned on?