User Guide

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 1–38) 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

1–41) 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 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.

Figure 16 Ambient Light Sensor Calibration window

RM-84/99

BB Troubleshooting and Manual Tuning Guide Nokia Customer Care

Issue 1 Company Confidential Page 1–39