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Mac SE SCSI Woes



As the title describes, my beloved Mac SE is facing problems pertaining to the use of SCSI devices.

I began to suspect something was wrong when my Mac failed to recognise any SCSI drives - this includes a fully-functional BlueSCSI device and two internal SCSI hard disks.

Upon further inspection of the logic board, I found that the CR1 diode had blown; this lead me to believe someone or something had forced something that was not SCSI compatible into any one of the SCSI ports.

In an attempt to rectify the issue, I replaced the blown CR1 diode with one of approximate value. This did not work.

With one step of troubleshooting undergone, I'm beginning to think that the AM5380PC SCSI controller is fried.

Is it worth sourcing a replacement chip?

If so, what are the difficulties associated with such a task?


Well-known member
It's definitely worth it given the high prices older Macs are bringing these days. Getting it installed is another matter. If you don't already have soldering skills learning by trying to replace that chip on your SE's motherboard is a bad idea.

I can't remember, does the SE use a DIP (pins go through holes in the motherboard) or a PLCC (pins curl under chip and sit on pads on the surface of the motherboard) 5380?

I think the PC at the end of the part number means it's a DIP, but I'm not sure.

I'd post your location and see if there's a list member local to you who can do the work, if you can't. Shipping costs can add up to as much as hte parts and a good bit of the repair. Questcomp.com has the chip is stock for about $15, which seems kind of steep. $10 each if you buy 4 or more. :)

Anyway, I'd wait until you find someone to do the work to worry about the part, as the solderer might have parts on hand or know a better source.

Also, I'm not sure, but you may be able to subsititute a Zilog or NEC 53C80 which should use less power and run cooler.


@trag , thank you for replying. And, after having another look at the board, I can safely say that the chip in question is a DIP chip. I'll see if I can find any data sheets for the chips that you mentioned; by doing this, I can see if the chips are suitable.

If anyone is wondering, I am located in the North East of England.

I remember reading this forum post https://68kmla.org/bb/index.php?threads/macintosh-se-superdrive-floppy-and-scsi-issues.7215/ and becoming worried that a chip replacement would be in vain.

I'm wondering whether or not I should just purchase a Floppy Emu device and save myself some hassle. Though this seems like an easy way ouy. ;)