Mac+ won't boot but gives startup tone

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Joined: Feb 1 2024 - 18:56
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Mac+ won't boot but gives startup tone

I pulled out my Mac+ out of storage and tried to boot it up today. It gave me the start up tone that sounded correct, but the screen was black with a messed up looking insert disk image in the center. I put in a bootable disk, but nothing happened. Restarting the machine gave me the same results. I took it apart, cleaned up both boards (being super careful to respect the high voltage on the one for the monitor) and didn't see any clear signs of damage to either one. Does anybody have any suggestions on where to start for troubleshooting this? 

 

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Joined: Feb 27 2021 - 18:59
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sad mac

That isn't the "floppy disk" icon: it's the "Sad Mac" icon indicating that the computer's built in self test (or POST) failed, with a numeric code below corresponding to the failed test state. It's hard to see because the graphics output is corrupted.

This is not an analog board problem. It's a problem on the main logic board.

The error code looks like "01FDFF". The "01" part indicates that the self test failed its initial sanity check (ROM checksum verification and hardware initialization), before it started the RAM test. So the problem isn't isolated to the memory. Additionally, the graphics corruption shows that the framebuffer in memory is getting corrupted, either when the CPU writes to it, or when the logic PALs read it out to the display, so there is likely to be a problem affecting data or address lines on the board.

Sometimes reseating chips can help with problems like this. Did you see any sticky or tacky, fuzzy gunk on the circuit board, evidence of leaked liquid from a capacitor? It can start corrosion which breaks copper traces on the board.

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