OK, it's definitely the display board. The replacement board came Friday, I installed it today and all the characters are displaying correctly.
The old board is now in the antistatic bag that the replacement came in. I say "old", but looking at the numbers following the part number (9522YG49 on the original, 8425YG37 on the replacement) and the use of Carbon comp vs film resistors (a mix on the original, all Carbon comp on the replacement) I think that the replacement board might actually be older than the faulty one. As and when I have some time, I'll read the numbers on the DIP ICs and see if I can figure out which might be the shift register. Visual inspection under a strong light didn't reveal any obvious dry joints, but I'll look a bit closer with a lens. After that, my options range from tapping the pins with an iron, in case a minor reflow fixes it, to just replacing it - TTL is cheap, after all, unless I get all obsessive and start looking for an IC with the right date code, which could happen. ;-) It never hurts to have a spare. Speaking of spares, the same seller has several other 5110 cards. No CPU, but he does have some Read/Write Storage. Does anybody know whether upgrading the memory is as simple as plugging in another board, or does it involve wiring changes to the backplane, or other complex manoevres? -- Robert
