Apple IIGS ADB Port Still Not Working

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ZangLucarson's picture
Last seen: 2 years 7 months ago
Joined: Apr 24 2021 - 20:23
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Apple IIGS ADB Port Still Not Working

Hi all, I've started two previous forum topics for this subject about two months back but still have been unable to solve the issue.I've been away for a couple months and caught up in other things in my personal life so I haven't had any time to work on this issue until now. I figured I'd round up everything I've troubleshooted from my previous forum posts, and put them all here, in hopes that I can get some new eyes on this issue.

As a summary, I obtained an Apple II GS ROM 3 several months back, and everything was in working order. There was hardly any corrosion or dust on the inside, and the clock battery had not begun to leak yet. 

In an effort to prevent any future battery leakage, I purchased a kit to replace the battery and its socket. After doing so, everything seemed to work fine afterwards, to the best of my knowledge the ADB keyboard and mouse were still working. 

I left the computer alone for about a week, purchased a serial to USB cable so I could run ADT Pro and do stuff on it, but when I went to boot it up, it turned on just fine, but the keyboard and mouse were non-functioning. 

After inspecting the main board, I realized that i'd accidentally damaged two traces near the battery, and the solder pad on the positive terminal for the battery was missing. I created a sort of jumper cable to where the terminal was supposed to go, and checked continuity, tried to test the keyboard again with no luck. 

For everyone's ease of understanding, here is a full list of everything I remember testing so far:

  • Checking continuity for the ADB cable (solid connection, the cable seems fine)
  • Checking the ADB filter (There was continuity between pins 1&8, 2&7, and 3&6, to the best of my knowledge that's how it should be)
  • Checking the ADB ports on the keyboard and main board (all pin terminals are clean, the terminals connect to their solder points.)
  • Testing the possibly damaged traces (neither of them seem to be related to the keyboard, and their continuity seems to be fine)
  • Testing fuses (There are none on the IIGS or the Original ADB keyboard to the best of my knowledge)

I've determined almost certainly that the issue is due to something on the main board. The fact that it doesn't work with either just the keyboard or just the mouse shows that. I do recall having tried to hot-swap the keyboard at times when I just got the computer and didn't know what I was doing, but the keyboard seemed to still work even after doing so. My last suspect is the KBD MICRO and KBD GLU chips, but if something is wrong with them then I really don't know what I'm gonna do because there doesn't seem to be anywhere to buy replacement chips.Here are some photos of my board. 

The red wire in the photo of the back of the board is the jumper cable. The keyboard and mouse were not working before and after soldering in that cable. 

If clearer photos are needed, I'll take some when I get home. 

Anything helps at this point, if anyone has any alternative methods of input, that would be quite useful as well.