Towards the end of WOzFest 18, frequent attendee Andrew and I started to look into the use of the ROMX programmable ROM product in a pre-Revision 7 motherboard.
This requires a different character generator (CHARGEN) chip, and also the replacement of two logic chips that aren’t next to each other (the ROMX designers have created a U-shaped sub-board to allow the non-adjoining chips to be replaced in one go).
I only have one pre-Revision 7 board – something Andrew and I determined after checking each and every europlus board I have (not a small task, as those who know me understand). And, of course, it’s in my “to-be-refurbished” pile, so I wasn’t sure it would work. In fact, with several missing logic chips, I could tell it wouldn’t, so off we went scavenging the needed chips to try and get some joy.
However, joy was not to be had – we were unsuccessful in booting, but I could see a non-standard font was being used, so partial success as far as the character generator goes.
At this stage of the night, I was not up to pulling out my logic chip tester and working through the board, so we called it a night.
But this isn’t a single-board consideration for me. I have quite a few boards I need to check and try to get up and running, and that’s daunting enough that I have procrastinated on that part of my europlus Refurbapalooza.
I gotta say here, though: I promise the next step is not a further pit of procrastination – but I decided if I was going to check this board, I needed a resource to help me do so which might be usable on other boards, and, if it takes several sessions, to keep track of where I was at, and also to maybe record some other salient information about the board I was working on.
With my experience designing the “WOzFest Labs Apple Astec Power Supply Unit AA11040B/C Electrolytic Capacitor ‘Spec & Check’ Sheet” (over four years ago!), I thought I might be able to do something similar for Apple ][ motherboards – of course, it would have to have different versions for the main motherboard revisions, so you can see why there’s a risk it might end up being a useful way for a procrastinator to put off productive work!
But I’m a New Age Procrastinator! I’m happy to
wastespend time preparing for a small job while accommodating the larger task it’s a part of. So for the last week I’ve been working on test sheets based on Winston D. Gayler’s RFI motherboard block diagram on page 177 of The Apple II Circuit Description. I’ve also referenced Jim Sather’s Understanding the Apple II, which, in Appendix G, details revision differences.
The result? Four test sheets covering the major revisions of Apple ][ and ][+ motherboards:
The sheets show most major components, including product codes, which motherboard product codes are relevant for that revision, areas to record info like case and PSU serial numbers and notes, and an area to record the dates of test sessions and progress through the board.
I would suggest first filling out the serial numbers, date code and (if not standard for the board) crystal frequency, along with any other salient info in the Notes area. Then mark missing (or clearly damaged) components with a red pen.
When testing components, I would mark bad components with a red pen and good components with a green highlighter. When bad or missing components are replaced, highlight with a green highlighter. Whether pads are cut or soldered can be indicated as well.
If switching components from other boards, some collectors might like to indicate that either at the component location or in the Notes area. Most collectors would likely be able to identify individual motherboards by date code – for those with larger collections with duplicate date codes, perhaps a numbering scheme will be need to be implemented by those collectors.
I’ll be leaving a test sheet in each of my machines not only to easily identify them and their operational status, but also keep track of any other work I might be doing on the machine (replacing speaker foam, etc.).
I want this to be as useful a resource for the community as possible, so any suggested changes are welcome. While I won’t be working on other Apple ][ models, I’m happy to discuss with others such sheets and provide info and files.
I’m now actually looking forward to the next stage of motherboard refurbishment, knowing I have the info I’ll need and an ability to keep track of each motherboard’s progress, as I rarely get enough time to work through a whole board in one sitting.