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Checkerboard Pattern on Mac 512

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Hey guys! Have another question for you guys


Yet another entry in my Macintosh 512 repair saga. Previously, I fixed the analog board, discovered I had no roms and ordered them. Today, I plugged them into the board, however the issue of the checkerboard is still persisting. When I turn the power on, i get a "PRRRRR" from the speaker in place of the startup "bong" noise, a small bit of activity from the drive and that's all. What is going on here? I can also send more pictures if that is required.


Any help is welcome







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3 hours ago, macfan2350 said:

If I put a disk in, it will just linger there. No activity

That's expected behavior for a machine that does not chime and shows a checkerboard pattern. The "small bit of activity from the drive" may be the track 0 calibration. The 400K Sony drive pulls its head back to track 0 at power-on.


Check your ROMs. They look homemade and suspect. Maybe they need to be reseated. Maybe they need to be replaced.




1 hour ago, Crutch said:

Sorry, what is that upgrade board on the left?  From the other thread, were you guessing that’s a 512k upgrade to the 128k motherboard?  How is it attached?  What happens if you remove it?  Just curious ....

I counted sixteen 256-kilobit DRAMs, so that's probably a 512K upgrade board.


Also: is it just me, or are an awful lot of those ICs soldered on the motherboard bearing a 1986 date code?

Edited by Dog Cow
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