Apple //e power supply (was Re: Which Apple II?)

[mjmahon@aol.com (Michael J. Mahon)]

Sheldon Simms wrote:

<snip>

>P.S. On another topic, my IIe power supply died last week. I just
>swapped it out with a spare I had, but I'd like to know what might
>be wrong with it. When it was still in the IIe, the symptoms were
>that you could turn on the computer, and after 2-5 minutes, the
>power would simply cut off. If I tried switching it off and on
>again, it wouldn't power up. If I switched it off and then waited
>a while before switching it back on, then it would come up for the
>above mentioned 2-5 minutes. This started happening suddenly about
>a week ago. It's the first problem I've had with the computer at
>all since it was bought in 1983.

This symptom is characteristic of a power supply which has
become marginal, and is falling over the edge when its
temperature rises.

The supply can almost certainly be rejuvenated by replacing
the high voltage electrolytic capacitors on the "line" side of
the supply.  They are typically 200-250v capacitors.  As
these capacitors age, they lose capacitance and their
equivalent series resistance increases, both of which
reduce the efficiency of the line-powered DC supply (which
powers the switcher).

When you get into the supply (assuming you want to fix
it) it's a good idea to clean it out and make sure that the
heat sinking is still good so that it runs as cool as possible
to prolong its life.  (Of course, a fan helps too, but you're
probably already using one of those.)

-michael

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