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I'm trying to fix my LC 575 sad mac.


It was working up until a point last year, when it started to sad mac at random. At which point I realized that the caps had leaked.


I proceeded to wash the logic board and recap with tantalum capacitors.


Unfortunately the sad mac faces continued. I've washed the board several times to try and rule out cap juice. They symptoms went from being slightly random to very consistent.


I've removed the hard drive and I've only got a cd-rom installed. I've also removed the battery.



Here are the symptoms.


I power it up. And I get a good chime, followed by a disk with a flashing question mark.


If I insert a bootable cdrom I get a sad mac (I've tried both my LC 575 restore cd with 7.1 on it as well as my Mac OS 8.0 cd)


If I insert a bootable floppy disk I get a sad mac.


The sad mac codes are as follows (its fairly random which one shows up):


0000000F 00000001


0000000F 00000002


0000000F 00000003


0000000F 0000000A



Googling seems to turn up that these are some kind of bus errors coming from a corrupt boot record (which is impossible on the CDs) My theory is that there is some kind of rotten trace that is not preventing any of the self-diagnostics on power up, but when data starts being sent to the processor it comes up corrupt on the other side of the bus.


Any ideas as to if there is anything I can do to recover this board?



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I spent some more time on this and I'm starting to suspect a bad CPU. I put a cold pack on the logic board and set it on the cpu for about 10 minutes. Then I put the board in the machine and tried it again. This time it booted, but within a minute or so of reaching the desktop It bombed with an illegal instruction. Any thoughts on ways to confirm this without buying a CPU? I don't want to waste any more money than I absolutely have to.

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