Okay, so more research is never a bad thing. I dug around a little and came across a copy of Sun Remarketing’s Do-It-Yourself Guide for the Apple III. You can download it in PDF from 1000bit’s documentation archive here, and if you ever have to do any hardware troubleshooting on a pre-Plus version of an Apple III, I highly recommended consulting this guide.
Serial #018052, which I’d decided to try to bring back to life first, is one of the early 12V 128K Apple III units, released just after the recall, but before the introduction of the ‘revised’ 5V Apple III. This isn’t a III Plus – those came much later, in 1984. Apparently the III Plus was only on the market for a short time, the damage in the public’s perception of anything with an Apple III label having already been done, so it sold in very low numbers and while functionally not much different, today it’s a much rarer commodity and more highly desired by collectors.
At any rate, #050756 is also a 12V unit, so I’m thinking I could scavenge it for working parts. Serial #051780 is a 5V machine, and for the purposes of fixing #018052, of little use.
I ran the in-built memory diagnostic mentioned in Sun’s guide and discovered that two of the RAM chips on the Apple III Main Memory board were bad.
Bad RAM chips, as indicated by inverse blocks in the memory map
I borrowed two chips from 050’s board…
A healthy RAM board passes the diagnostic
As an aside, I also discovered that the memory board in 050 was installed backward and may have been at least partially behind the unit’s earlier complete boot failure. Getting 050 up and running again may not be as daunting as I’d thought.
Now to address the 018’s floppy issue. Again, an easier fix than I’d expected. The floppy cable was plugged into the wrong port on the analog card. Moving it to the correct one brought it back to life, at least to the point where it tries to read a disk at power on. It may have other issues (timing is apparently a big one with these drives), but until I fire up ADTPro and transfer over some disk images to real floppies, I won’t know.
The drive tends work better when it has been properly cabled.
Finally, there’s the issue of the case. This is mostly a cosmetic thing and one I’m not as worried about, though I am looking forward to experimenting with Retr0bright. The cases haven’t been too badly abused, suffering only light scratching, dirt and the requisite yellowing that comes with age. I picked what I thought was the best of the three and did a little basic cleaning with some 409 and paper towels. The final result? Not too bad, I think.
Not as pretty as the day it was manufactured, but closer than it was a few days ago.
Still to do: dig out the Apple Monitor /// that’s supposed to go with this thing; whip up a batch of Retr0bright and get to transferring disk images.
Given the condition of 050, that will probably be my next Apple III project. I suspect tracking down the replacement parts needed will be the hardest task. Anyone have a good source for Apple III keycaps and 12V RAM chips?