Hill-Rom Advanta P1600, Service Manual

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Theory of Operation
Chapter 3: Theory of Operation
Advanta™ Bed Service Manual (man168ra) Page 3 - 19
3
accessory connectors available for future needs on the power supply P.C.
board. The unregulated voltage is monitored by a circuit that disables the relay
power supply and the PPM/Scale module. Line voltages, or loads that create
unregulated voltages less than approximately 10-12 volts, disable the output of
the relay/Scale/PPM power supply. Recovery occurs when the line voltage or
load condition returns to normal.
The power supplies are independent and unique. Each has its own protection
from overload, that prevents one output load issue from bringing down the
entire system. The air system module has built-in current-limiting in the
design; all others are protected by current/temperature protection PTC’s. The
PTC is sized within a module current requirement and duty cycle. All fuses are
soldered in the board. Fuse failure is remote and usually indicates failure of a
primary power supply component. Fuse rating and part number must be
identical to maintain regulatory approval of the bed power supply.
The ground fault circuit measures the voltage differential on the neutral line
coming in to the bed. This particular circuit is referenced to the bed chassis
ground. Any differential greater than approximately 6 volts turns on the FET
and, therefore, turns on the emitter follower that outputs to an optocoupler
which isolates to the logic control P.C. board. This allows detection of a loss of
ground or a phase-neutral reversal to be determined.
The night light circuit is a comparator circuit that determines a reference point
via an adjustable potentiometer, and a CdS photocell that determines resistance
based on ambient light. A regulated power supply is connected to the
comparator circuit and the DC bulb used for a light source.
The power supply is linked to the logic control P.C. board via connector P7
using a cable, part number 6148904. A regulated voltage and current-limited
supply is sent to the relays used on the logic control P.C. board. A regulated
voltage and current-limited supply is also sent to the logic control regulator.
The scale and PPM module is supplied pre-regulated voltage that is current
limited. The interconnect scheme is a connector P13 and a cable, part number
63727. There are two nurse Call signals brought to the power supply P.C.
board to connect to the communications junction box assembly.
The Universal Television (UTV) and communications junction box assembly
is supplied two pre-regulated voltages that have current-limiting protection.
The interconnection is presented by connector P12 and a cable, part number
63726. The power supply has interconnections for Nurse Call signals that are
generated by the scale and PPM module.