Power
Supply
The system
DC
power supply is a 63.5 watt, 4 voltage level switching
regulator.
It
is integrated into the System Unit
and
supplies power for
the System Unit, its options, and the keyboard.
The
supply provides 7
amps
of+5
Vdc,
+5%
2 amps
of
+12Vdc,
+5%
300 rna
of
-5Vdc,
~+IO%
and
250
rna
of
-12 Vdc,
+10%.
All power levels are regulated
with overvoltage
and
over current protection.
The
input is 120 Vac and
fused.
DC
over-load
or
over-voltage conditions exist, the supply will
automatically shut down until the condition
is
corrected.
The
supply is
designed for continuous operation
at
63.5 watts.
The System Board takes approximately 3 amps
of
+5 V dc thus
allowing approximately 4 amps
of
5 V dc for the adapters in the System
Expansion Slots.
The
+ 12 V dc power level is designed to power the
two internal
5-1/4" Diskette Drives and the system's dynamic
memory.
It
is
assumed
that
only one drive motor is active
at
a time. The
- 5 V dc level is used for memory bias voltage and analog circuits in
the diskette adapter phase lock loop.
The
+12 V dc and
-12
V dc are
used for powering the serial interface card
EIA
drivers
and
receivers
for the Asynchronous Communications Adapter. All four power levels
are bussed across the five System Expansion Slots and available
for option adapter.
~
The IBM Monochrome Display is self-powered. However, the high
resolution display receives its
AC
power from the System
Unit
power
system.
It
is switched
on
and
off with the power switch, which saves a
wall outlet. The
AC
output for the display is a nonstandard connector,
so only the
AC
high resolution Display
can
use this
AC
port.
2-33
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