Description
The system power supply
is
located at the right rear of the system
unit. It is an integral part of
the
system-unit chassis. Its housing
provides support for the rear panel, and its fan furnishes cooling
for the whole system.
It
supplies the power and reset signal necessary for the operation
of
the system board, installed options, and the keyboard. It also
provides a switched ac socket for the IBM Monochrome Display
and two separate connectors for power to the
5-1/4
inch diskette
drives.
The two different power supplies available are designed for
continuous operation
at
63.5 Watts. They have a fused 120 Vac
or
220/240
Vac input and provide four regulated dc output
voltages: 7 A at
+5
Vdc, 2 A at + 12 Vdc, 0.3 A at -5 Vdc, and
0.25 A at -12 Vdc. These outputs are overvoltage, overcurrent,
open-circuit, and short-circuit protected.
If
a dc overload
or
overvoltage condition occurs, all dc outputs are shut down as long
as the condition exists.
The + 12 V dc and -12 V dc power the EIA drivers and receivers
on the asynchronous communications adapter. The
+12 Vdc also
power's the system's dynamic memory and the two internal
5-1/4
inch diskette drive motors. It
is
assumed that only one drive
is
active at a time. The +5 V dc powers the logic on the system
board and diskette drives and allows about 4 A of
+5
Vdc for the
adapters in the system-unit expansion slots. The -5 V dc is for
dynamic memory bias voltage; it tracks the
+5
Vdc and + 12 Vdc
very quickly at power-on and has a longer decay on power-off
than the
+5
Vdc and + 12 Vdc outputs. All four power supply dc
voltages are bussed across each
of
the five system-unit expansion
slots.
Power Supply
3-3
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