Apple II Computer Info
rather
than internal, power supply.
SWITCHING-STYLE POWER SUPPLIES
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Power supplies for electronics are of two general types: (a)
step-down transformers with DC rectifiers and one or more secondary
windings,
and (b) switching power supplies which rectify the AC power to DC, then
create the target voltages by rapidly switching the power on and off.
Switching power supplies include complex regulation and protection
circuits
so that power is turned down if the target voltage strays beyond the
limits
of narrow acceptable ranges. Switching power supplies are more expensive
but
safer; they are used in all computers including Apple II, IBM, and
Macintosh.
SWitching power supplies can fail, but when failure occurs the output
voltage drops rather than going berserk, as can happen with others.
APPLE II AND IBM POWER SUPPLIES: BASIC FEATURES
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Apple II and IBM power supplies share similarities: Both are
designed
as switching (internally protected) power supplies; both give the same DC
output voltages (+5v, +12v, -12v, -5v). Both are designed originally to
be
installed inside the computer.
The Apple II power supply delivers about 45-60 watts. It is fully
enclosed, has no fan, and has a difficult-to-replace internal soldered
fuse.
The IIe/II+ version uses a 6-pin motherboard plug (Molex red brick
miniature
rectangular Matrix housing, Digi-Key part no. A14113-ND). The IIgs
version
has a brushed aluminum housing with different mount, and a distinctive
motherboard connector plug (Molex .156" 7-pin center-crimp terminal
housing
with locking ramp; Molex no. 09-50-3071, Digi-Key part no. WM-2105-ND).
The
Apple II power supply is adequate for the average user, but inadequate for
"flagship" Apple IIs loaded with RAM, extra cards, or more than two disk
drives. Symptoms of power overload "brownouts" include spontaneous
crashes
and "freeze-ups" that require rebooting. With adequate power capacity,
crashes and freeze-ups should not occur.
IBM-style power supplies are big and impressive. Even the smaller
IBM-style power supplies deliver 150 watts, 2.5 times the output of the
standard Apple II power supply. Newer models deliver 200-300 watts and
may
be smaller in physical size than the older 150 watt models. All have
cooling
fans; most have selectable dual input voltages: 110/220v AC.
Nearly all IBM power supplies run cool when used with Apples; the
fan is unnecessary. Even after many hours of continuous use with the
Apple, IBM power supplies generate little or no noticeable heat. Lack of
Apple II Computer Technical Information : Apple II Family Hardware Info
ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 48 of 572
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