Re: Apple Power Supply Questions

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

capknight wrote:
> On Apr 12, 7:39 pm, capknight <cepheusfi...@gmail.com> wrote:
> > Hello,
> >
> > I picked up a number of active and dead power supplies recently. A few
> > are the AE Vulcan GS supplies, AE IIe Supplies and original OEM Apple
> > supplies.
> >
> > Some were dead but I was able to resurrect them by replacing the
> > electrolytic capacitors.

Yes, I have a couple of supplies to do the same surgery on.  ;-)

> > The readings are a bit odd on the Vulcan GS supplies. I've listed them
> > below with modified and unmodified numbers (meaning I replaced the
> > caps in one and left the other original).
> >
> > The negative 12 volt leg seems really low on the Vulcan GS supplies as
> > well as the re-capped AE IIe supply.

Since I presume these are unloaded voltages, they are solely the result
of inaccuracies in the windings of the high frequency transformer.

The voltages you report are all within tolerances for the uses that
the supplies are intended for.

> > I did not test the Vulcan GS supplies with the 105mb hard drives
> > installed. I was able to find re-certified drives that work just fine
> > with the Vulcan GS cards.

I'm curious about which drives you found that work...

> > Testing was done straight from the boards and not through the cables.
> >
> > One thing I did note on the Vulcan GS supplies is that the gauge of
> > the wires from the 120v receptacle to the switch and board are very
> > thin in comparison with the other supplies.
> >
> > Any thoughts?

That shouldn't make any difference.  The total power drawn by the supply
is well under 100W, so the line current is under 1 ampere.  Any slight
voltage drop in the line section is regulated out by the supply.

> > Thanks!
> >
> > C
> >
> > Modified Vulcan GS (caps replaced):
> > ================
> >
> > -4.32
> > -10.07
> > +12.19
> > +5.47
> >
> > Fan: +12.17
> >
> > Molex for HD:  (red) +5.46
> >                    (yellow) +12.17
> >
> > Unmodified Vulcan GS:
> > ==================
> >
> > -4.27
> > -10.05
> > +12.13
> > +5.42
> >
> > Fan: +12.11
> >
> > Molex for HD:  (red) +5.47
> >                    (yellow) +12.08
> >
> > Modified Applied Engineering IIe Supply (caps replaced):
> > ============================================
> >
> > -4.99
> > -11.6
> > +12.03
> > +5.28
> >
> > Unmodified Apple IIgs Supply:
> > =======================
> >
> > -4.98
> > -12.13
> > +11.24
> > +5.05
>
> I forgot to note that I did make some slight adjustments to the pot on
> the board to see if I could move the voltages around a bit. It helped
> on the AE IIe supply.
>
> Thanks,

The only actively regulated output is the +5v--all the other voltages
are supposed to track that voltage open loop, just by virtue of the
transformer winding ratios.  The adjustment is for the +5.

Standard Vcc tolerance for TTL is 5v +/- 10%, so anything from 4.5v
to 5.5v is within spec (though timing margins will vary somewhat
over that range, the parts should continue to meet spec).

The other voltages are less critical, particularly the negative
voltages.

-michael

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