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Troubleshooting
13.
Date and time are now correct. Check by switching on the N-20P with the printer enabled.
After the N-20P executes its Power-On Self-Test, the printer prints the spot check mode
header with the correct date and time.
4.6.4
Replacing the Real-Time Clock (RTC) Battery
The socket for the RTC battery (BT1) is located on the auxiliary PCB at grid location 5D.
Typical life of the clock battery is 5 years.
1.
Disassemble the N-20 (see Section 5.3, N-20, Disassembly Procedure).
2.
Using a thin flathead screwdriver, gently pry the RTC battery from its socket.
Insert a new battery into the socket, observing the polarity indication (socket's clip and
3.
battery's flat side are positive).
4.
Reassemble the unit.
5.
Reset the clock (see paragraph 4.6.3, Setting Date and Time).
4.6.5
Replacing Fuses
Two fuses (F1 and F2) are located on the auxiliary PCB. Fuse F1 may open to protect the CPU and its
associated components from damage if the power supply malfunctions. Fuse F2 may open to protect
the printer from damage due to excessive voltage if the printer head jams or has been physically
damaged. Refer to the auxiliary PCB schematic for the locations of F1 and F2.
4.6.6
Replacing the DB-9 Connector
1. Disassemble the N-20 (see Section 5.2); the connector is on the main PCB at grid location 3A.
2. Using a low-power soldering iron, unsolder the connector from the PCB and remove it. Save all
Teflon tubing, ferrite blocks, and insulating materials for the replacement connector.
3. Install ferrite blocks between plastic lead spacer on the connector and the PCB.
4. Insulate connector pin numbers 2, 3, and 5 with Teflon tubing, and insert inside ferrite block.
5. Add insulating material between each end of ferrite block and PCB, and secure with Loctite glue.
6. Solder new connector to PCB and visually check PCB for stray drops of solder before
reassembling.
7. Switch on the N-20/N-20P and test the connector with a patient sensor.
4.6.7
Adjusting Printer Darkness
Caution: Adjust the printer darkness setting until the lightest legible print is visible.
Setting the print darker than this could reduce the life of the printer-head. Although the N-20P is
designed to automatically compensate for conditions that might influence the quality of the printout,
the user may want to adjust the print darkness. The normal darkness setting is set at the factory; this
setting maximizes both readability and life of the printer-head.
1. Switch on the N-20P in spot check mode. (Depressing the instrument Measure button once starts
Spot-check mode.)
2. Simultaneously press and hold the ADV and ON buttons for 2 seconds. If these buttons are not
pressed at the same time, two audible beeps will sound and the N-20P either advances the paper
or switches off, depending on which button press is first sensed. If the buttons are pressed at the
same time, a single audible beep will sound, Pr SEt is displayed, and the printer prints one of the
following 6 lines:
PRINTING LIGHTER
PRINTING LIGHT
PRINTING NORMAL
PRINTING DARK
PRINTING DARKER
PRINTING DARKEST
4-6
(10% lighter than normal darkness)
(5% lighter than normal)
(normal darkness)
(5% darker than normal)
(10% darker than normal)
(15% darker than normal)
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