Covidien Nellcor OxiMax N-560, Service Manual

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Technical Discussion
N-560 Service Manual 113
Power Supply PCB Theory Of Operation
The N-560 uses a switch mode power supply. This Power Supply provides the
DC power needed to charge the battery and to power the Main PCB.
Electromagnetic Static Discharge (ESD) protection is also provided by the
power supply.
AC power is passed through a step-down transformer. The transformer’s
secondary winding is fused with two 2.0-amp fuse. If a short circuit occurs in
the DC circuitry, these fuses prevent the transformer from overheating. The
output of the transformer varies, depending on load and input. High frequency
noise from the AC line and from the Main PCB is filtered by R1 and C1
before passing through the bridge rectifier.
The bridge rectifier provides the DC power used in the N-560. The positive
output is the MAIN_DC of 14 volts DC. This positive voltage is used for the
battery circuit and to power the Main PCB.
Battery
A nickel metal hydride battery is used in the N-560. It is rated at 9.6 volts DC,
3.8 amp hours. When new and fully charged, the battery will operate the
N-560 for eight hours. A new battery will last 15 minutes from the time the
low battery alarm is declared until the N-560 is shut down due to battery
depletion.
The battery can withstand 400 charge/discharge cycles. Recharging the
battery to full capacity takes 6 hours.
Changing from AC to battery power does not interrupt the normal monitoring
operation of the N-560. When the N-560 is running on battery power, the data
port will be turned off.
Main PCB
The Main PCB is the heart of the N-560. All functions except the unregulated
DC power supply, display, and keypad reside on the main PCB. The
following text covers the key circuits of the main PCB.