HP 3000 SERIES II System Service Manual page 167

System Service
A4 Current Limit PCA
A5 Voltage Protect PCA
A6 5V/30V Rectifier Assembly
A7 Inverter PCA
A8 Deck Assembly
A9 Preregulator Assembly
A10 Connector Panel Assembly
A12 Front Panel Assembly
A12A1 Test Point PCA
A13 Output Crowbar Assembly
30310-60005
30310-60006
30310-60011
30310-60007
30310-60014
30310-60010
30310-60012
30310-60013
30310-60001
30310-60015
The power supply is a modular unit mounted in the cabinet by means of hinges. The unit swings out
on the hinges for service and is removable from the hinges for replacement.
WARNING
Two men are required to remove the HP 30310A Power Supply
from its mounting hinge. This power supply weighs 50 pounds
(22.7 kilograms).
A POWER switch which is on the front panel of the power supply (see figure B-6) turns the unit on.
(Note however, that a DC Enable (DCE) signal is required at terminal 1 of terminal board TB3 to
enable the output voltages.) Circuits within the power supply provide normal operation and failure
warning signals to the CPU. The status and control signal connections at terminal board TB3 and
the output DC voltages at TB1 are cabled to their destinations at the factory. The output voltages
and the Power On (PON) signal are accessible on the front panel for measurement. In addition, an
indicator lamp is mounted on the front panel near the test points to monitor the +5 volt output.
Refer to table B-1 for HP 30310A Power Supply specifications.
B-3. THEORY OF OPERATION
The theory of operation is divided into two sections. A general description at the block diagram
level is presented first, followed by a functional description at the simplified schematic level.
The power supply converts a 208/240-volt, single-phase, 50- or 60-Hertz power source to regulated
DC supply voltages for system operation. An HP 30312A Power Supply augments the +5 volt
output of this supply.
A POWER switch, mounted on the front panel of the supply, controls the AC input to this unit.
The DC output voltages can be controlled by the SYSTEM switch which is mounted on the DC
Control Panel (see figure B-6). The output voltages provide status signals for protection of software
(information stored in CPU memory). Computer system hardware is protected by circuits that sense
overvoltage, overcurrent, or overtemperature conditions. Circuits within the power supply are
protected by various overvoltage and overtemperature circuits, current limit circuits, and fuses. The
general concept in the power supply design is to immediately turn the power off when an
overvoltage condition occurs. For undervoltage or over temperature conditions, a short delay is
generated before the power supply is turned off. This delay permits the CPU to store data which, in
turn, makes power on and restart much easier.
B-2 JAN 1977