On Wed, 17 Sep 2014 14:30:18 -0700 "Loren M. Lang" <[email protected]> wrote:
> I'm assuming the power supply voltages are out of
> spec so I pulled out my voltmeter. Measuring the SATA power connector
> with the dead hard drive attached and Mac powered on, I found 5V on
> the 5V supply lines and no voltage on the 12V or 3.3V lines. No
> indication of something that might kill a logic board, but I would
> expect to see 12V on the supply.
Okay, this is wrong. There should be a +12V supply at the drive pins.
It's not surprising that there isn't a +3.3V logic supply. Most
drives don't use it, so most manufacturer's don't provide it.
However, the 12 volt supply is required, and should always be
there. Did you measure the voltages with the drive plugged in or
not? The presence or absence of a load can make quite a
difference.
Also, did you check for an AC component on the supply pins? Or
better yet, use an oscilloscope on them? It's entirely possible
to have high-amplitude AC coming out of the power supply, yet
still have it read the proper DC voltage with a meter. That sort
of thing can fry your logic board. (Heed the Voice of Experience,
my son.)
Hope this helps.
--Dale
--
Imagine if every Thursday your shoes exploded if you tied them the
usual way. This happens to us all the time with computers, and
nobody thinks of complaining.
-- Jeff Raskin
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