A while back I built the Apple Lisa 2-Port Parallel card that AlexTheCat recreated and posted on GitHub.
However, during assembly, I reversed two chips, the 74LS109 at B2 and the 74LS280 at C4. When I first tested it, I found out that upon plugging a Profile in (even if the Lisa was off), the Profile would not enter self-test. Instead, the ready light would stay on till the card/cable was disconnected. This doesn’t happen when the card is out of the machine, but happens in all slots and both ports.
I’ve tested all chips except for the 6522 (which I replaced with some spares I had) using a T48, which said they were all good (The 74LS244 at 5D was reporting bad initially but it turned out to be that I inserted it wrong into the T48). I’ve since desoldered everything from the board as well (with exception to caps and the ports) to see if any of my solder was making contact (nope).
I’m currently at a loss, has anyone here seen this sort of behavior?
However, during assembly, I reversed two chips, the 74LS109 at B2 and the 74LS280 at C4. When I first tested it, I found out that upon plugging a Profile in (even if the Lisa was off), the Profile would not enter self-test. Instead, the ready light would stay on till the card/cable was disconnected. This doesn’t happen when the card is out of the machine, but happens in all slots and both ports.
I’ve tested all chips except for the 6522 (which I replaced with some spares I had) using a T48, which said they were all good (The 74LS244 at 5D was reporting bad initially but it turned out to be that I inserted it wrong into the T48). I’ve since desoldered everything from the board as well (with exception to caps and the ports) to see if any of my solder was making contact (nope).
I’m currently at a loss, has anyone here seen this sort of behavior?
