Nellcor Oximax NPB-40, Service Manual

Page: 44 / 114

Troubleshooting
36
• The CPU PCB is defective. Replace the CPU PCB with a known good PCB. See CPU
PCB or Display PCB Replacement on page 46.
The display backlight does not come on when the
Backlight
button is pressed.
• The
Backlight
bottom on the front
panel keypad is defective.
Caution: Unlock J3 before attempting to
remove flex circuit conductor.
Open the NPB-40, disconnect the front case from J3 on the
CPU PCB and connect an ohmmeter lead to the flex circuit
conductor for J3, pin 3 and individually connect the other
ohmmeter lead to each conductor for the buttons. Refer to
the front panel schematic diagram (**). Observe a short
when the button is pressed and an open when the button is
not pressed.
If incorrect, replace the front case. See Front Case Assembly
Replacement on page 49.
If correct, replace the CPU PCB. See CPU PCB or Display
PCB Replacement on page 46.
• Flex circuit between the front panel and
the CPU PCB is disconnected.
Inspect the flex circuit and reconnect if the flex circuit is
loose. See Separating the Front and Back Cases on page 44.
• A CPU PCB Component has failed. Inspect the CPU PCB components and circuit board for
cracking, burning, or damage and replace the CPU PCB if
any are found. See CPU PCB or Display PCB Replacement
on page 46.
• CPU PC has failed. Replace the CPU PCB with a known good PCB. See CPU
PCB or Display PCB Replacement on page 46.
• The
Backlight
LEDs on the Display
PCB have failed.
Replace the Display PCB with a known good PCB. See
CPU PCB or Display PCB Replacement on page 46.
The NPB-40 shuts off when the
Backlight
button is pressed.
• The batteries are at or near a voltage too
low for the NPB-40 to operate.
Install new batteries. See the NPB-40 Operator’s manual.
The printer does not print.
• The printer and the NPB-40 are not
properly aligned.
Align the printer and the NPB-40. See the NPB40
Operator’s manual.
• The printer is turned off. Turn the printer on. See the printer documentation.
• The
Data
bottom on the front panel
keypad is defective.
Caution: Unlock J3 before attempting to
remove flex circuit conductor.
Open the NPB-40, disconnect the front case from J3 on the
CPU PCB and connect an ohmmeter lead to the flex circuit
conductor for J3, pin 3 and individually connect the other
ohmmeter lead to each conductor for the buttons. Refer to
the front panel schematic diagram (**). Observe a short
when the button is pressed and an open when the button is
not pressed.
If incorrect, replace the front case. See Front Case Assembly
Replacement on page 49.
If correct, replace the CPU PCB. See CPU PCB or Display
PCB Replacement on page 46.
Table 3:
Troubleshooting Guide
(Continued)
Condition Recommended Actione