I never used a Performa 638 CD so I’m curious if it has “server mode” just like a Mac IIsi where the on button in the back is able to be turned to the on position on a permanent basis? Therefore a shutdown will actually not happen. On the IIsi the button just turns and locks in the on position...
To make the repairs necessary or to make the necessary repairs? Big difference. Anyone can make the repairs necessary. Doesn’t need to be a professional.
In the eBay listing description put something to the effect of...
"Modern technology and ambitious Macintosh developers have made it possible to replace the failed SCSI hard disk drive with newer storage options."
Then give them a Youtube link with a demonstration. From the demo they can figure...
You could just remove the hard drive and sell it without one. Whomever buys it will probably add SCSI to SD option.
If the Mac worked then you could obtain a bootable floppy disk with a formatting utility on it to boot the Mac and erase the hard drive. You simply insert the obtained floppy and...
I'm remembering back when everyone wanted to list the uptime of their Mac in chatrooms and forums. Meanwhile I was constantly rebooting mine to get a stable running system. Seems like so long ago. Maybe it was.
BTW try this it may help. https://macintoshgarden.org/apps/mac-restart-0
The Mac SE shipped from the factory with 1 MB installed in the form of four 256 KB SIMMs. It can be upgraded to 2 MB, 2.5 MB, and 4 MB configurations using 150ns or faster 1 MB 30-pin SIMMs.
A Mac SE can boot from a CD but Mac OS 7.6.1 will not work on it. Mac OS 7.1 would be a good start...