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IIfx Restoration Issues


Active member
This is a very helpful thread. I have two Mac IIfx boards with battery vomit. I have been gradually cleaning them up and have had similar damage and issues, especially with the death chime.

Today I was finally able to get one board to start up after I found a small broken trace on the back of the board on the line from Battery 1 to D6. Just like yours it will not shutdown. I've got voltage to UI18 (when on). I do take extensive voltage readings, on the shutdown circuit. On Q2, I am getting 0v on pin 1 (emitter), 0v on pin 2 (base) and 4.4v on pin 3 (collector - single bottom pin). The resistor associated with it I get 0v on both sides. I do have continuity. I'm still stumped on shutdown. Reading your comment about UE13 and UD13 was helpful. I will recheck that area.

Even with finally getting it to boot from the start up button (I have been jump starting both boards) I would immediately get the death chime. I will look into buying the ROMinator, maybe that will help. I will also check my ROM socket.

Also reading about your issues with the BlueSCSI is interesting. I just bought three kits and haven't had a chance to build them yet. I also have a Mac IIx that I recently finished.

Thanks again for the insight, I will continue to follow this thread.


Well-known member
Well, I'm back from my vacation, and unfortunately bad news. My IIfx is insta-death chiming again. It's literally been sitting on the side for 2 weeks not doing anything and it was in its semi-working state before I left. So I've no idea what's causing this. I think I'm gonna try bodge-wiring in the RAM chip for the Serial ASIC to bypass the broken traces and hopefully I might be able to get something out of the modem port that might indicate why it's failing POST.


Well-known member
Are you still using the purple PCB RAM from one of your earlier pictures? Maybe try swapping original RAM back in to eliminate the Purple PCB RAM variable and get back to semi-working status? I think some custom ROMS had different PCB thicknesses that could cause contact issues over time- not sure if the purple RAM have the same issue? Easy thing to try anyway :)


Well-known member
It would also be interesting to know what happens when you try the BlueSCSI internally with nothing connected externally. Try with / without the BlueSCSI terminator jumper(s?) set. The IIfx is supposed to have a special "black" SCSI through-terminator for external devices. I saw a post recently about this, will try to find it and link here.


Well-known member
The IIfx is supposed to have a special "black" SCSI through-terminator for external devices

The black terminator is needed because it is better than a normal passive SCSI terminator which just uses resistors. A more recent active terminator should, as I understand it, be even better than the black terminator, and so if you're using an active terminator I believe you shouldn't need to worry about the black terminator.

I am open to being wrong, though. :)


Well-known member
I haven't messed with my IIfx enough to say one way or 'tuther. I also don't have one of those "magic" black terminators... but I do have a couple of active ones, as well as some grey (platinum?) "through" ones. 🤔