Joined: July 14th, 2009, 9:14 Posts: 1 Location: Boston, USA
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I had a similar failure - in my case the IC at 3a is the one that has failed - this is the motor controller TLS2501 - a comparison against a 'good' drive from eBay showed no pulse trains coming out of that chip.
(Not surprising, as the drive came from a mac which was powered on while soaking wet. Fuse etc. were fine but the motor drive was burned out.)
Unfortunately as 3a is a BGA I cannot just swap the motor controller from the good board to the bad (I don't have access to a BGA rework oven).
The replacement drive I have is about 1 year newer (Dec 08) and has the masked ROM in the CPU IC 2b, whereas the original failed drive has the separate 5a ROM chip.
i.e. the reverse of the problem described here
BUT this is why I am posting - the same firmware version is marked on both drives. i.e. "Apple firmware A07" - so even though one drive has masked ROM and the other has discrete ROM, they are the same so the NVRAM should be compatible.
I moved the serial NVRAM/EEPROM from the failed board 4a to the replacement 4b, and it worked fine. i.e. the drive spins up and the data can be accessed.
Just thought that might be useful for others following this thread - i.e. if you can't find a 100% identical drive, check the firmware versions - you might get lucky!
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