Hi, I purchased a fine looking Kaypro 4/84 a little while ago, and for the most parts it seems to be in good condition. But it has this really irritating vertical jitter or shaking, not so bad that it can't be used, but irritating still. The vertical motion is something like a scanline or two in heigh, and it's really straining my eyes.
I have some experience with fiddling around with old portable TV's and CRT monitors, so I know how to now get zapped while working with these things. I have dismantled the tube and boards and changed all the capacitors, but that didn't seem to help. The video board is made by Toshiba and has 20-pin TA7634AP IC on it. I have tried to search schematics or datasheet for those, but can't seem to find any.
I tested the tube without the motherboard and cranking the brightness all the way up so I can see the raster, and that seemed to jitter also. Playing with the pots didn't have effect on the problem. I also tried feeding the board with a good ATX power supply, and the problem persists. I have oscilloscope at my workbench, but without schematics for this board, I don't know what I should look for.
If anyone with some more experience has any suggestions on where to start nailing down this problem, help would be greatly appreciated.
I have some experience with fiddling around with old portable TV's and CRT monitors, so I know how to now get zapped while working with these things. I have dismantled the tube and boards and changed all the capacitors, but that didn't seem to help. The video board is made by Toshiba and has 20-pin TA7634AP IC on it. I have tried to search schematics or datasheet for those, but can't seem to find any.
I tested the tube without the motherboard and cranking the brightness all the way up so I can see the raster, and that seemed to jitter also. Playing with the pots didn't have effect on the problem. I also tried feeding the board with a good ATX power supply, and the problem persists. I have oscilloscope at my workbench, but without schematics for this board, I don't know what I should look for.
If anyone with some more experience has any suggestions on where to start nailing down this problem, help would be greatly appreciated.