Nokia 9000i Service Manual page 259

After Sales
Technical Documentation
1.1.1.17 Is N83 pin 1 toggling?
There should be seen about 300kHz voltage toggling between 0V and
VBatt. In oscilloscope there should be seen about 20 pulse sequences at
irregular pulse group periods. If not go to 1.1.1.18. Otherwise if there are
pulses coming to N83 pin 1 in continuous train the regulator is 'saturated'.
Check that valid LCD voltage is seen at C89 positive terminal. Measure
LCDVEE current with UI module connected. If current is higher than 4mA
big LCD in UI module is probably corrupted.
1.1.1.18 LCDVEE controller fault
Replace N83.
1.1.1.19 Is V89 anode voltage toggling?
There should be seen irregular shaped voltage bursts at peak magnitude
between 0V and valid LCD voltage (little higher). Voltage bursts decrease
in magnitude during their period. The bursts appear at irregular time
intervals. If not go to 1.1.1.20.
1.1.1.20 Check L81, V81, R77, R74, R85
Most probably V81 is broken. Check and replace. If not helping check
L81 and R74, R85. These resistors provide current feedback information
to the controller. There should be seen increasing voltage spikes at peak
magnitude of a little less than 300mV. If yes L81, V81, R74 and R85 are
OK. Then check and replace V89.
1.1.1.21 Is there valid bias voltage at C89 plus terminal?
Measure DC voltage over C89. It should be within 20V – 24V at room
temperature. Measure also peak–to–peak AC voltage from 100ms
sample. It should be less than 100mV. If not go to 1.1.1.22. If yes go to
1.1.1.23.
1.1.1.22 Check V89, C89 and feedback resistors
First measure voltage from N83 pin 3. It should be exactly 1.5V. If yes
replace C89. Also check C95 and V89. If not check resistance and
replace if needed for resistors: R84, R82, R78, R93 and R97. Also check
C79.
1.1.1.23 Check V87, V82, R95, R98, R94
The fault is that the regulator works correctly but the switch between the
regulator and LCD module is broken. This switch is needed to totally cut
voltage from LCDVEE line. First measure collector voltage of V87. It
should be near 0V. If not check and replace V87, R95 and C98. If yes
replace V82. Also check R94 and R98.
Original, 05/97
RAE/RAK–1N
Faultfinding/Disassembly
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