superjer2000
Well-known member
I just finished recapping 3 Mac Classic logic boards.
When starting them up, two displayed horizontal lines on boot (not garbled, just perfect ~4 pixel wide horizontal lines).
When taking them back to the garage to clean them up I noticed that the ROM on the board I had just powered up felt warm. That prompted me to realize I made a silly mistake: I didn't notice there was an extra row of pins on the side of the ROM socket and for two of the boards I had the ROM in the wrong pins.
I fixed the issue and tried to boot the boards. This time 2 of the three worked and the last one still had the same lines.
By swapping ROMs across the boards and I was able to validate that one of the ROM chips itself was causing the problem. I'm not sure if the chip was ruined when it was plugged in to the wrong set of pins on the ROM socket, but I'm thinking probably not given that the other ROM chip is still working fine. I'm posting this as I've read a number of posts regarding these horizontal lines and none of them concluded on the issue.
TL;DR: If your Macintosh Classic boots up with horizontal lines/bars either your ROM chip is defective or one of the traces going to the ROM socket is defective.
When starting them up, two displayed horizontal lines on boot (not garbled, just perfect ~4 pixel wide horizontal lines).
When taking them back to the garage to clean them up I noticed that the ROM on the board I had just powered up felt warm. That prompted me to realize I made a silly mistake: I didn't notice there was an extra row of pins on the side of the ROM socket and for two of the boards I had the ROM in the wrong pins.
I fixed the issue and tried to boot the boards. This time 2 of the three worked and the last one still had the same lines.
By swapping ROMs across the boards and I was able to validate that one of the ROM chips itself was causing the problem. I'm not sure if the chip was ruined when it was plugged in to the wrong set of pins on the ROM socket, but I'm thinking probably not given that the other ROM chip is still working fine. I'm posting this as I've read a number of posts regarding these horizontal lines and none of them concluded on the issue.
TL;DR: If your Macintosh Classic boots up with horizontal lines/bars either your ROM chip is defective or one of the traces going to the ROM socket is defective.