Re: Turn on Apple to preserve it?

["Paul G." <carbide@egine.com>]

On Mar 12, 9:00 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> This will re-form the electrolytics in the 120v section of the supply,
> which is the biggest source of problems.
>

That's very useful info, Michael. I had a weak power supply that would
click for a while but eventually come up and boot the computer.  I
don't have a variac, so I tried leaving it on all day in the hopes
that would reform the electrolytics. It seemed to make things worse.
Plan B was replacing the caps. I keep a box of PC power supplies to
scavenge for parts, and was able to find suitable replacements.

Replacing the electrolytics in the 120V section did the trick.  It
boots right up now.    I have an ESR meter (effective series
resistance) which I built from a kit back when I was repairing
monitors. That is useful for quickly finding dried out electrolytics
in circuit, but it did not identify these as bad. They only measured
about twice as high as the replacement parts- typically bad parts
measure 10 times higher.  So your suggestion that the weak link was
the 120V caps was a great help.
-Paul