68kMLA Classic Interface
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| Troubleshooting a broken M0110A Keyboard? | |
| Posted by: dv- on 2025-10-09 10:21:34 Anybody have (or know where I can get) wiring diagrams for a Mac Plus Extended keyboard? I have one that's just a doorstop; other keyboards work fine with the same Plus / cable, but this one does nothing. I'm specifically curious about how to test that big microcontroller. (Would I need, like, an oscilloscope app?) The contacts grid seems to check out alright, so I think the traces on the board are ok (a few scuffs and scratches but continuity is good.) I replaced the two barrel caps; the resistors checked out ok, per my multimeter. Resoldered everything else just 'cuz. I've read that if they're unplugged/plugged back in during operation, or used with an incorrectly wired headset cable, they can very rarely get fried - is there any deeper info on what happens when that occurs? TIA | |
| Posted by: Wiggs1979 on 2026-05-26 11:15:13 I realise this is an old post, but I purchased a M0110A keyboard from a well known auction site and it was basically a doorstop. Like yourself, I tested all the passives and they all checked out okay, indicating it had to be the controller chip. Once you've narrowed it down to that though, I don't think you can really do much more than replace it. I probed it with a logic probe for the clock signals, but it appeared to be dead. Fortunately, I have an old EPROM programmer that can handle chips like 8748 and it didn't take too much searching to find a ZIP file with the code for the keyboard controller - search for mackbd and you'll probably find it. With the keyboard being a single-sided Mitsumi PCB, a hot iron with a bit of solder wick made light work of removing the faulty 341-0332, fitted a socket and dropped in a programmed NEC D8748D and I am back in business, a fully working keyboard.   If anyone needs an 8748 programming, I'm happy to help out (I'm UK based). Last I looked, the supplier I bought mine from only had one left, very tempting to pick it up as a spare since I know that supplier is good. | |
| Posted by: obsolete on 2026-05-26 14:38:58 That's awesome! Great fix. | |
Posted by: shirsch on 2026-05-27 07:17:38I realise this is an old post, but I purchased a M0110A keyboard from a well known auction site and it was basically a doorstop. Like yourself, I tested all the passives and they all checked out okay, indicating it had to be the controller chip. Once you've narrowed it down to that though, I don't think you can really do much more than replace it. I probed it with a logic probe for the clock signals, but it appeared to be dead.I have searched Google for 'mackbd' and cannot find anything on point. Would you mind posting a link? | |
Posted by: Wiggs1979 on 2026-05-27 12:40:19I have searched Google for 'mackbd' and cannot find anything on point. Would you mind posting a link? Hopefully this isn't against the rules given that it's for something that's long out of production. Edit: Removed link. | |
| Posted by: shirsch on 2026-05-27 13:17:02 Thanks, but I'm not seeing a link for download at that page. I suspect membership is required? | |
| Posted by: Wiggs1979 on 2026-05-27 13:21:58 Sorry, that was the wrong link, it's been too hot here to think straight, especially when you have a soldering iron next to your face! I actually downloaded it from here. https://68kmla.org/bb/attachments/mackbd_m0110a-zip.42635/ | |
| Posted by: shirsch on 2026-05-27 15:19:44 Thanks much! | |
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