A1286 820-2915-B no boot


I have an A1286 820-2915-B, that doesn't boot. It shows the Apple logo, the loading bar starts to load, but then the logo disapers and the screen stays a bit light grey.
Already replaced the disk, and the disk cable, but with the same result.

Without the disk, the question mark signal stays on screen forever.

Don't know where to start. Can you help?
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Staff member
Classic GPU problem.
The image disappears at the moment macOS tries to load GPU driver.
Easy to disable in BIOS, or flashing GMUX.
no I haven't done it before. I've set a firmware password now, but it worked for a few times, and them it gets the same behavier, even with the firmware password
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