68kMLA Classic Interface
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| Click here to select a new forum. | | Macintosh Plus mouse doesn't move | Posted by: lastfreeusername on 2025-05-30 15:41:59
Hi 68kMLA! I am completely stuck with my Macintosh Plus, and I don't know what to do. The situation: Macintosh starts, boots with chime, and OS initiates. Mouse click is working, but the mouse doesn't move. What I did:
1. I checked connectivity inside the mouse, all photoresistors, and diodes. Everything is fine.
2. I ordered a new M0100 mouse and tested it - the same status.
3. I checked the connectivity of the port and up to the VIA chip. Everything seems fine and connectivity for X1, X2, Y1, Y2 is fine. The same for resistors.
I am really stuck now, cause I don't believe that chip itself is an issue. The computer is in a very good condition – the only thing is that one memory socket clip is broken, but it can't affect, since the POST chime is here.
Could you give me some ideas where I can look for the issue? | Posted by: cheesestraws on 2025-05-30 15:54:42
You say you checked to the VIA - did you also check X1 and Y1 going to the SCC? Responsibility for dealing with the quadrature signals from the mouse is split between the VIA and SCC. I think it's the SCC that generates the interrupt that is actually used to detect mouse movements, so it might be worth checking the wiring back from the SCC as well. | Posted by: lastfreeusername on 2025-05-30 15:57:29
Thank you! Yes, I also checked wiring to the SCC, and those are also fine, can get a beep out of both. | Posted by: cheesestraws on 2025-05-30 16:11:59
OK - forgive me, I am working from memory here, not at home. Next thing I might check would be that the INT output of the SCC is going where it ought to.
Do you have access to an oscilloscope or similar? | Posted by: lastfreeusername on 2025-05-31 08:28:30
I have access to the proper lab, yes, oscilloscope should be there. Could you please guide me what exactly should I expect to have? | | 1 |
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