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HP 32421A Series III Power Supplies
a.
Power down the system by placing the corresponding
UPPER
or
LOWER MEMORY DC POWER switch
on
the
Dc
Control
Panel
to
STANDBY
and
place
the corresponding HP 30311A Power Supply
switch off (down).
b.
Disconnect plugs P2, P3, P4, and P5 on the rear panel of
the
power supply.
c.
Remove the power supply from the cabinet.
d.
Remove top and bottom covers from the power supply.
e.
Free the
motherboard by
removing four screws,
two from the
top and two from the bottom edges of the rear panel frame.
f.
Disconnect plug P6 on the motherboard.
g.
Slide the
two boqrds
out of the
rear
of the
power supply
fr arne.
h.
Remove the control board from Jl and the motherboard.
Note
Steps i and j should be performed when the
motherboard and heat sink are
to
be
re-
placed.
i.
Remove four screws holding the motherboard to the rear panel.
j.
Remove four screws securing the heat sink to the rear panel.
The motherboard
and heat sink are replaced by using
the reverse
order of
the
above
procedure.
Power supply
output voltages
should be checked after replacing the motherboard.
9-33. HP 30312A OPERATION
The HP 30312A Power Supply (figure 9-1) provides up
to
100
am-
peres of 5-volt power for operation of the interface PCA's in the
I/O area of the computer.
The power supply is an HP 62605M Power
Supply modified by adding a power switch,
fuse,
ac
receptacle,
and
a
threshold
adjustment
circuit.
The threshold adjustment
circuit is adjusted when the
system
is
configured
to
provide
overcurrent shutdown of the HP 62605M Power Supply when the drain
on the
power
supply
exceeds
a
predetermined
amount
by
ten
amperes.
The following discussion covers only the items and circuits added
to the
HP
6260SM
Power Supply.
The HP 62605M Power Supply is
described in
Modular Power
Supplies,
Land
M Series,
Models
62605L, 62605M, and 62615M Manual, part no. 5950-1756.
The Model
62605M is equipped with cption 106 which enables the power supply
to operate
on 187 to 250 volts
ac input power.
'I'he HP
303l2A
Power Supply provides 5-volt power over a current range nominally
9-21
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