Re: IIe power supply problems

[adrianw@cassius.ee.usyd.EDU.AU (Adrian Whichello)]

In article <4r8bdd$8n1@atlantis.atlantis.actrix.gen.nz>,
David Empson <dempson@atlantis.actrix.gen.nz> wrote:
>In article <ggonter-2906960026140001@port-50-max-btv-02.ramp.together.net>,
>Geof Gonter <ggonter@together.net> wrote:
>> I need a little help with a computer. I was given a IIe that would not
>> run. I believe it to be with the power supply I was successful in getting
>> the IIe to run, but there is a problem somewhere. The voltages check out
>> pretty close on the power supply and it will boot, if you slide the power
>> supply connector over the lugs and get the "Power On" light to come on. It
>> will even stay on if you push the connector all the way on. But, once the
>> power is cut, switch on power supply, pulling the plug, or turning off the
>> surge protector, the unit will not power up until the connector is pulled
>> and pushed down over the lugs in the connecting socket on the board.
>
>This may indicate a fault on the motherboard, e.g. causing a power
>supply short.  The Apple II supply is a switch-mode supply, and is
>designed to cut out if there is no load or too much load on it.
>

Although David is correct in assuming there could be a short, I also
experienced this problem with an old 2+ power supply. Eventually it became the
only way I could convince the computer to boot (by rapidly pushing the power
plug into the motherboard socket, with the power supply switched on). Another
supply went the same way and it ended up having to be "jump started" by using
5V from the bench power supply! Not good.

Unfortunately there are no good FAQ's for fixing Apple power supplies and
fiddling with them not for the faint-hearted, unless you like the odd belt off
the mains voltage. Oddly enough, power supplies from clones seem better than
Apple's own, even though they are usually made from lower quality components.

Adrian Whichello                           Phone: +61 2 351 4824
Imaging Science and Engineering Laboratory  Home: +61 47 588 319 
Sydney University Electrical Engineering     Fax: +61 2 351 3847
Australia                                  Email: adrianw@ee.usyd.edu.au

"I wish to God these calculations had been executed by steam!" - C. Babbage