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Macintosh 128k Help
Posted by: MacAttack on 2019-04-08 17:49:39
So, I posted here about a year ago about a 128k Macintosh that I got off of craigslist. Since then I figured out that the ram was bad and replaced it. I've got to a point where the computer functions but the video has a major issue. I have been unable to find the issue so far, so here I am again! For further reference, I do have logic probes and an oscilloscope at hand if that helps fix the issue.

(Before Ram Replace)

View attachment 21922

(After Ram Fix)

IMG_1184.JPG

IMG_1185.JPG
Posted by: Dog Cow on 2019-04-08 18:26:00
Where is your arrow pointer? When you move it around the screen, does it also show up more than once? Do you have two arrow pointers moving simultaneously?
Posted by: MacAttack on 2019-04-08 21:28:04
Yea, Everything appears to be mirrored three times, one on the right, one in the middle and one on the left.
Posted by: MacAttack on 2019-04-08 21:38:59
Here, I photoshopped about where the mirrors are occurring.

macs.jpg
Posted by: tattar8 on 2019-04-09 21:24:01
Could this be caused by a bad mux or demux (assuming the 128K has anything like that) causing the same data to be stored multiple times to the framebuffer?
Posted by: MacAttack on 2019-04-09 21:49:05
Probably not, I already replaced the MUX chips with brand new Motorola chips but this next chance I get I'll test them with my logic probe to see if I scorched the chips while soldering.
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