Table 5-6: Display/Audible Tones Problems - Mallinckrodt NELLCOR NPB-4000 Service Manual

Section 5: Troubleshooting
5.6.4 Display/Audible Tones
5-8
Table 5-6 lists recommended actions to address problems with the display and
audible tones.

Table 5-6: Display/Audible Tones Problems

Condition
1. System powers-up
and...
• LCD screen is totally
black or white.
Or,
• LCD screen is
illuminated, but no
data is visible.
Or,
• LCD screen has
data, but is not
illuminated.
2. NPB-4000/C
responds to switch
press, but key press
tone fails to sound.
Recommended Action
Note: Pressing the NPB-4000 contrast adjust
switch causes the LCD contrast setting to
immediately change to normal, factory-
default value. Pressing the NPB-4000/C
contrast adjust switch toggles the display
between the two different color schemes
(black background and white background).
1. NPB-4000. Adjust LCD screen contrast by
pressing contrast adjust switch momentarily,
then turning knob four revolutions in each
direction. Turning knob counter-clockwise
should brighten screen; turning knob
clockwise should darken screen.
2. NPB-4000C. Adjust LCD screen contrast by
pressing contrast adjust switch momentarily.
Screen will toggle background color.
3. Ensure red LED, located on top left corner of
main PCB is illuminated. If LED is not
illuminated, monitor is not in " on" state; follow
troubleshooting steps in paragraph 5.6.1.
4. Ensure backlight cable is connected to main
PCB and backlight inverter PCB.
5. Ensure LCD cable is connected to main PCB
and LCD PCB.
6. If problem persists, replace main PCB.
7. If problem persists, replace backlight PCB.
8. If problem persists, replace LCD assembly.
1. Ensure speaker cable is connected to power
supply assembly.
2. If problem persists, replace speaker
assembly.
3. If problem persists, replace main PCB.
Or