Ac Module; Primary Board - HP 9030 Service Manual

Theory of Operation
2-5
LEDs on the assembly indicate overvoltage or undervoltage conditions for dc supplies, as well as
overtemperature, peak power exceeded, and
110
door or processor stack door open.
The ac module consists of an on/off power switch/circuit breaker assembly, line filter, and an
attached ac power cord. Interconnection is made with two barrier strips and qUick-disconnect
terminals. A primary voltage change requires changing the switch assembly, power cord, and cable
that interconnects the line filter and power supply.
The power supply assembly is cooled by a dc box fan mounted on the chassis. The fan is not an
integral part of the assembly.
The power supply assembly has three printed circuit boards: the primary board, the secondary
board, and the supervisor board. The following description is organized according to the functions
performed by the ac module and these three boards.
The power supply assembly plugs into the motherboard in the computer base via six connectors,
two per board. These connectors, and their associated motherboard traces, interconnect the power
supply assembly boards, and carry voltage and signal lines between the power supply assembly
and other computer modules.
Fifteen status-indicating, light-emitting diodes (LEDs) are contained on the supervisor board. They
are described in a folloWing subsection in this chapter.
Ac Module
The ac module has an attached 6-foot line cord that plugs into an ac outlet. The line filter reduces
conducted emissions from the power supply assembly. It also presents the ac voltage to the on/off
power switch/circuit breaker which enables/disables ac power to the computer.
The trip point of the circuit breaker depends on which power configuration is being used. The 110V
breaker trips at IS amps line or line overvoltage. The 220V breaker trips at 10 amps. Reset the
circuit breaker by turning the switch off and then turning it back on.
Primary Board
After being rectified, the ac to the primary board charges two
2800~.Lfd
capacitors. Each capacitor is
charged to lS0-200V, depending on the line voltage and load.
The rectified dc voltage from the capacitors feeds a switching regulator. The regulator drives current
through the main power transformer.
Rectifiers at the output of the main power transformer develop the
+
SV switching supply. This
supply provides
+
S volts for use throughout the computer. The
+
SV output is monitored by the
supervisor board for overvoltage and undervoltage. Also, the
+
SV output feeds the pulse width
modulator. The modulator output controls the base drive which in turn controls the switching
transistors. The pulse-width-modulator-enable signal (PWM ENABLE) from the supervisor board
enables the modulator as long as no fault signal is present. A fault signal disables the modulator,
shutting down the power supply assembly.