Nokia RM-57, Service Manual

Page: 158 / 391

ALS troubleshooting
Context
If a phototransistor is broken, replace it with a typical phototransistor. The phototransistor has to be also
replaced, if calibration values are lost by some other reason (e.g. after replacing the NOR memory chip D3000).
If the phototransistor is changed, the calibration value in the phone memory has to be changed to the default
value ‘1’.
Make sure that you have completed
Display and keypad backlight troubleshooting (Page 6–37) first before
starting ALS troubleshooting.
Here are some hints for ALS troubleshooting; the following troubleshooting diagram refers to these:
• Phoenix LED control tool also shows you luminance. The correct luminance in darkness is <20lx, and in office
environment 100-2000lx. The luminance value depends strongly on the light source and the angle of the
phone, so these values are only a rough guideline.
• LED driver control voltage measurement points can be found from LED driver troubleshooting (Page
6–41) section. When backlight brightness is set to 100%, both GENOUT-signals are low, and enable PWM is
100%.
• Phoenix has an ambient light sensor calibration tool for changing calibration values. The pull-up resistor
calibration is done first:
a Cover the light guide (upper part of the A Cover).
b Click 'Start' and 'Write'.
c Manually change the ambient light sensor value to the default value. There is no special tool for this, but
you have to perform calibration normally and then set the "Co-efficient" result to '1' before writing it to
the phone memory.
RM-57/58
Nokia Customer Care BB Troubleshooting and Manual Tuning Guide
Page 6–38 Company Confidential Issue 1
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