Nellcor N-180, Manual

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Section 5: Troubleshooting
5-3
You see CHE LED displayed for a few seconds; then, 0 is displayed..
2. You can then sequentially light each LED segment by slowly rotating the
control knob clockwise.
3. When the display reads 126 you have tested all the segments.
4. Turn control knob a bit more; the segments in the numeric displays
(SpO
2
and heart rate) turn from green to red. Turn control knob a bit
more and these segments turn red.
To check the front panel buttons:
1. Press the high saturation button and rotate the control dial
counterclockwise.
2. You see CHE 1 in the display .
3. Press each control button; verify the respective LED to the left of each
button lights.
The number of lighted bars corresponds to the number of DIP switches
set to on.
To check the speaker.
1. Rotate the control dial counterclockwise until CHE 2 is displayed.
2. Press high saturation button to sound the alarm at maximum volume.
3. Press low saturation button to sound the alarm at minimum volume.
4. Press audio alarm off button to silence the alarm.
Even though you can precisely determine which LED segment is bad, the
replacement part is at the PCB level. Nonetheless, verifying a bad segment is
a good way to confirm your diagnoses before replacing the LED driver PCB
and LED PCB combination.
When you encounter a front panel display problem, use the decision tree in
figure 5 -1 (four parts) to find and replace the most likely component that
could cause the symptoms you observe. The right side of the tree points to
specific tables that describe exactly which components to remove and replace
or other appropriate action you should take. Bold lines in the decision tree
mark choices that lead to a table printed opposite the tree.