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Fix0ring a Macintosh IIfx


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@hyperneogeo  is a great seller, perhaps contact him directly on this site to arrange a purchase; his new modules work beautifully.  IMO it's worth upgrading a Mac such as this as they're one of the best vintage Macs to own, and you can come across random Nubus cards to shove inside and make it unique :)



Active member


Lil' update on the floppy drive, again:

I rooted through my spare parts to find a replacement for Q4, for the sake of testing. So basically I tacked on a through-hole transistor, but as long as it's the correct type and can withstand the load, it'll be good for testing purposes. Noting that the original transistors are rated for 0.7A, and the circuits they're in drive the head motor (and possibly other motors).

I connected the drive for a test run, and... poof, magic smoke.

Guess Q3 shat itself too, as after that I had a shitty 5V on the head motor controller, but the 12V was good. I replaced Q3 as well, and went for another test run. No magic smoke this time, and the drive head moved to track0 without issue.

Maybe these transistors wear out more when the drive is full of dust and crap and things move difficultly, which would explain this failure mode.

The drive is now sorta-working... I need to readjust the various alignments now, but I managed to make it mount some disks. I'm going to see after I get proper replacements for the bad transistors. The eject motor is still weak too, it's driven by Q9 so that one may be bad too.

... so basically we've been recapping vintage computers for a while now, but is 'retransistoring' a thing? :p



Active member
So what have we been up to since the last time?


My IIfx now has a whopping 20MB of memory. I basically sacrificed the extra 1MB SIMM I had, seeing as it wasn't gonna be useful for anything anyway, and replaced the chips with compatible 4MBit chips. I had to rewire one connection, too.

I'm still open to getting a 4x16MB set and cranking this up to 80MB, but, hey, the frankenSIMM was fun to make, in a way.


I put some more effort into the RF shield:


Most of the rust has been removed, through a mix of mechanical and chemical rust removal. Now, this thing isn't gonna look factory-fresh, unless I go through the trouble of re-plating it, which, well...

I'm probably going to go with some spray paint, ideally conductive. The IIfx doesn't seem to have entirely separate digital/analog grounds like some other Mac models, but I guess the RF shield would better be connected to the ground anyway.

The floppy disk bracket thing needs some derusting too. The case itself may use a good cleanup and maybe a retrobrite... might as well do it while I have the RF shields removed, but I'd need to get some supplies for that.


As far as the actual computer goes, I still need to fix or replace the floppy drive. I'm afraid I might have ruined the read head. We'll see once I get the new transistors, I guess. I know a place that may have oscilloscopes and shit, which might help me realign the heads properly.

The HDD, not sure how good it is. I can connect it to the computer and read what's in it without trouble, even running some mahjong game that's in it... but I can't boot from it, it gets stuck on the welcome screen. The HDD from my LC does the same thing, but that one was basically duct-taped back to life (it had a case of the melting head bumps), so I wouldn't give it much credit... I can however boot fine from my SCSI2D. I wonder if there are some SCSI termination shenanigans involved? The original HDD has terminators installed, and upon inspection of its controller board, I found out it also has the active-termination capacitors (which seem to be what the fancy IIfx terminators are about).

The Disk First Aid utility fails to do anything to that HDD, for whatever reason.

I'm also considering what I can do regarding video output.

I guess once these are sorted, I can start using this IIfx for evil projects >:)



Well-known member
Thanks for all the kind words everyone. @Arisoturaif you are interested in RAM I'm always here or on Ebay. I do sell them cheaper here than on Ebay as well. Basically take 15% off the Ebay listing. 

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