The most common failure items in these old Macs are the analog board and floppy drive. If your computer has a good analog board you can almost certainly find someone who doesn't want to pay $150 or more for a genuine Apple repair job.

Mac 128's and some 512's (the non-512kE) have a 400k single-sided floppy drive. This can only be used in a similar computer.

Some Mac 512's (the 512kE) and all Pluses and most SE's have an 800k floppy drive. These can be used to repair like computers and most Mac II (not IIx, IIcx, etc) computers. They can also be a second floppy drive for Mac II's.

A few Mac SE's (usually labled "FDHD" or "Superdrive") and all SE/30 and Classics have a 1.4Mb floppy that will work in any modern Mac, including models with the "non auto-inject" drives. This is a valuable piece of hardware (about $130 exchange at an Apple dealer) that you can almost certainly put to good use.

And finally, if you have a rare "FDHD" or "Superdrive" equipped Mac SE, you also have a set of ROM's on the logic board that could make a non-FDHD SE owner very happy. These enable the SE to use the 1.4Md floppy drive. If you want to know more about this, write me...