A few years ago, I won an Apple II Plus off of eBay that turned out to have a fault of some sort. After as much troubleshooting as my limited technical knowledge would allow, the problem persisted. I sought assistance on these boards, and after much back-and-forth over things to try and check...no luck. Eventually, an ugly thing known as life forced me to shelve the project.
Here is my original thread on the subject: http://www.applefritter.com/content/apple-ii-bad-memoryrom I strongly recommend you read the original thread, but if you're of the tl;dr mindset, I'll briefly summarize here:
- There appeared to be something wrong with the Applesoft E8 ROM the system originally came with. Replacing it with two different repro EEPROMs and socket adapter from Reactive Micro didn't remedy the situation.
- Running a diagnostic program shows ROM chips D0, D8 and E0 as having no errors. The test fails and then aborts on E8, so chips F0 and F8 never get tested.
- Various RAM chip swapping attempts didn't help, and all RAM tests passed with no errors.
- The system has a language card, but removing it doesn't remedy the problem.
- Attempting to boot from the DOS 3.3 disk crashes to the monitor when attempting to automatically load Integer BASIC, even if the language card is not installed. But, Integer can be manually loaded at the Applesoft prompt (With the language card installed), and afterwards Integer programs run normally with no errors.
- Binary programs run normally with no errors.
After three years, I finally decided to pull it out of the storage and try to tackle the problem again. I managed to snag an original E8 Applesoft ROM off eBay and have installed it...but it STILL isn't working properly. Attempting to boot DOS still crashes to the monitor and Applesoft programs will not run properly. Running the diagnostic disk continues to show the E8 ROM as being faulty. Although it is admittedly possible, I find it highly unlikely that I would have gotten FOUR faulty E8 ROMs in a row (The original the system came with, two from Reactive and the one I just now got from eBay). I know the language card is incompatible with the repro EEPROMs from Reactive, so it now gets removed whenever a Reactive chip is installed, yet the problem still persists.
Now, I will admit that I do have a little bit of concern about having possibly caused some damage to the system myself. When I received my first repro EEPROM from Reactive back in 2011, it did not include the required socket adapter. Not being aware at the time that it was a major no-no, I just plugged the bare EEPROM directly into the motherboard and powered it up. Could this have damaged the system? Beside that, there's also the concern of repeatedly pulling and reseating chips potentially stressing the sockets or the traces beneath them.
Assuming I didn't damage the board myself, I am starting to wonder if perhaps one of the logic support chips or perhaps some traces on the motherboard could be faulty, something that messes with the addressing for the E8 range. Therefore, I thought I'd ask the more knowledgeable people here for some further input on other areas of the board I could check, knowing that the RAM is good and assuming all of the ROM chips are good (Like I said, highly unlikely I'd get four bad E8s in a row). If it helps, here's the various revision and date marks I could find on the motherboard:
- In the far rear left corner is the date code 41 82
- Behind the card slots on the edge of the board is 606-X 548 MADE IN SINGAPORE
- Next to "F" on the left edge of the board is 820-0044-D (C)Apple 1979 Apple II Main Logic Bd RFI
My technical knowledge of the Apple II Plus is just as limited now as it was three years ago, and I am still no closer to solving this problem. Hopefully, with enough brain power from everyone else here, we'll finally get this issue licked, eventually.