Mac II Video glitch

[blturner]

I've been running in circles attempting to diagnose some garbled text when something is highlighted on screen. At first I assumed it was a RAM issue because I had been reconnecting traces on the problem board, but I've now encountered the issue on two Mac II's and a IIx. Snooper and APD have not found any issues with RAM. I have two Toby NUBUS graphics card and an Apple Display Card 8*24 where text gets garbled. I've booted from a BlueSCSi and a floppy disk and it persists. It seems to only happen on 256 colors. Millions is fine. I'm using a Dell LCD display with a DB 15-pin->VGA adapter, maybe that's all it is? I only have LCD displays so it's difficult to rule that out as the culprit. I mostly want to confirm that this is not an issue on the logic board so I can move on with repairs.

 

[David Cook]

I have two Toby NUBUS graphics card and an Apple Display Card 8*24 where text gets garbled. I've booted from a BlueSCSi and a floppy disk and it persists. It seems to only happen on 256 colors. Millions is fine. I'm using a Dell LCD display with a DB 15-pin->VGA adapter, maybe that's all it is? I only have LCD displays so it's difficult to rule that out as the culprit. I mostly want to confirm that this is not an issue on the logic board so I can move on with repairs.

Very interesting.

It isn't the LCD.

1. Does it happen every single time in 256 mode?
2. Is the scrambled text always scrambled the exact same way or does it look randomly scrambled differently each time?