Mallinckrodt Nellcor N-20PA Service Manual page 32

Troubleshooting
4.7.4 Replacing the Real-Time Clock (RTC) Battery
4-6
3. When dashes appear in the Oxygen Saturation and Pulse Rate displays, press
the D/D (day/date) button once. At this point, the Oxygen Saturation display
shows "txx", with "t" representing time; "xx" representing hours, and "yy"
representing minutes. Note that "xx" (hours) is flashing.
4. Press the ADV (advance) button repeatedly until the correct hour is
displayed.
5. Press the D/D button once. Note that "yy" (minutes) is now flashing.
6. Press the ADV button repeatedly until the correct minute is displayed.
7. Press the D/D button. At this point, the Oxygen Saturation display shows
"dxx", with "d" representing date; "xx" representing the day and "yy"
representing the month. Note that "xx" (day) is flashing.
8. Press the ADV button repeatedly until the correct date is displayed.
9. Press the D/D button once. Note that "yy" (month) is flashing.
10. Press the ADV button repeatedly until the correct month is displayed.
11. Press the D/D button. At this point, the Oxygen Saturation display shows
"Yxx," with "Y" representing "year". Note that "xx" (year number) is
flashing.
12. Press the ADV button repeatedly until the correct year number is displayed.
13. Press the D/D button once. The N-20PA turns itself off immediately.
14. Verify that date and time are now correct by switching on the N-20PA and
then enabling the printer. After the N-20PA executes its POST, the printer
prints the header with the correct date and time.
Note: The parenthetic line description is not printed. Button presses are
ignored whenever the printer is printing.
Note: If in the D/D mode and there is no user interaction (no buttons are being
pressed) for 60 seconds, the N-20PA turns off and any changes made are
not saved.
The socket for the RTC battery (BT1) is located on the auxiliary PCB. Typical
life of the clock battery is 5 years.
Caution: After replacing an RTC battery, switch the instrument on, then
immediately switch it off; this action will prevent possible damage to the
RTC voltage circuit.
To replace the real-time clock/battery:
1. Disassemble the N-20PA (see Section 4.3, Disassembly Guide).
2. Using a thin flat-head screwdriver, gently pry the RTC battery from its
socket.
3. Insert a new battery into the socket, observing the polarity indication
(socket's clip and battery's flat side are positive).
4. Reassemble the unit.
5. Switch on the instrument, then immediately switch it off (the RTC voltage
circuit requires this step to prevent possible damage to the unit). The
instrument is now ready for normal operation.