The cables have been checked, and the contacts lightly cleaned, and there is happily a considerably better display now. There remains some flickering, but no really bad multi-coloured (mostly orange, and yes, on a B&W screen) effects. The ghosting is also greatly diminished.
The flickering is not down to the backlight, as the flicker (now reasonably slight) persists even when the backlighting is off and you look at the thing in bright light.
The service manual mentions a shim that needs to be installed on some models to improve the contact between cable and display hardware as a solution to video flickering. I had a close look at that connection point and applied all sorts of pressure in an experimental effort to see if any such pressures would make a difference. None did. What I did discover, however, is that if I touch the cable, even lightly, the flickering disappears. Evidently there is some electrical reason for this (grounding?), but I am not sure what it would be, being electrically challenged.
Any ideas out there? I'd like to restore this thing back to life, and ideally install that Japanese System 6 version that will run on the PB 140-145-145b series on it. Mind you, for a speedly OS, read on:
Here's another thing, thought it is strange to tell. What I have really is a PB145: 25 MHz 68030, 1-bit screen, 6 MB RAM, and so forth. I stuck a larger scsi drive in it (250MB or some such; the original was dead) and installed System 7.1 this morning, as it was handy. To my wonder and delight, the thing boots in about 10 seconds, from bong to desktop. How is that possible? My Performa 600 (cough) that was my first Mac ran 7.1 for years and took about an hour to boot (I exaggerate only slightly), and it was supposedly a 33 MHz machine. Surely the improved bus speed in the PB doesn't make it that much faster, does it?
