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I bought an LC 475 for parts and repair on ebay. When it arrived it seemed to work okay but the video was all stripey. After some diagnosing I spotted a rotten trace near the the VRAM simms. I repaired the rotten trace with a jumper and I got my video working. But now I've got chimes of death.

Removing the the ram upgrade fixes the chimes of death and allows the machine to boot. However when I reinstall the ram (or known working ram from other machines) I'm back to death chimes and no video (I don't even get a sad mac with a hex code)

I've hunted for other rotten traces on the board, but I'm not having any luck. What should I try next? (It's so frustrating that this was working. I've traded one problem for another.)

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I fixed it.

I used a known working logic board from a different mac and a multimeter set to continuity to find the bad trace.

first I tested the first 16 pins of the simm slot to the ground on the scsi port on the working board for reference resistances.

Then I compared them on the bad board, I found that pin number 9 was open when it should have matched the resistances of pins 8 and 10. From there I followed the trace leading from that pin until I found a scratch that I aparently gave it when I was fixing the first problem. (I should be more careful next time) I jumped the bad trace and now all is well.

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