Re: Caps a poppin!

["Michael J. Mahon" <mjmahon@aol.com>]

Charlie Springer wrote:

> Either way, I would check the power supply. I get a lot of //e's with bad 
> power supplies. Something in those Apple switchers does not age well. Often 
> they will display symptoms much like you describe. Sometimes pulling all the 
> boards out will lower the current enough for the supply to run correctly and 
> boot OK. I have a box of new (new old stock, as they say) supplies from Sun 
> Remarketing (and a box of new keyboards for Platinum //e) which 95% of the 
> time is all that is needed to fix up a dead Apple.

Usually the problem is aging electrolytic capacitors, particularly
in the AC line-powered capacitor-input power supply to the switcher.

When the primary filter cap(s) lose capacitance, the voltage to the
switcher drops too low for it to maintain regulation, shutting down
the supply.  These capacitors are generally in the 150v-250v range,
as opposed to all the other electrolytics, which are in the 25v range,
and are at the power switch and bridge rectifier end of the supply.

-michael

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