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RM-12
Backlight troubleshooting (2)
Start
Disable backlight
from Control Panel
D4420 pin #8 = 0V
Check VBAT availability through
current path from following points.
1. L4426
2. C4420 & C4421
3. R4423 & L4421 & V4420
4. C4443 & C4424
5. L4422 & C4428 & C4429 & C4425 & R4430
Replace series components
before point where VBAT
voltage is lost. Start from battery
side VBAT.
Check also C4423 and
R4446 (value = 27R) soldering.
Check X4421 pin soldering.
C4425 =
VBAT?
No
PWB failure
Issue 1 11/2004
Use partial mode or
adjust brightness period
to lowest value to disable
display backlight. Verify
functionality with working
display unit.
D4420 pin #8
= 2.78V
Enable backlight
from Control Panel.
Full brightness
Yes
COMPANY CONFIDENTIAL
Copyright © 2004 Nokia. All Rights Reserved.
Nokia Customer Care
Backlight OK?
No
Replace D4420.
Check also with
another display unit
after component
change.
Backlight OK?
No
PWB failure
END
END
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Table of Contents
Troubleshooting
