Nokia 9000i Service Manual page 260

RAE/RAK–1N
Faultfinding/Disassembly
1.1.1.24 LCDVCC OK?
Command LCDVCC on by PCLocals. Measure voltage from LCDVCC
line. If the voltage differs from Vsys value go to 1.1.1.25. When LCD
module is not connected verify also LCDVCC off state by toggling the
control by PCLocals.
1.1.1.25 Check V80, V86
Transistor V80 gate is pulled down by transistor V86 to enable LCDVCC.
Identify and replace the faulty transistor. If not helping then check also
R81, R72 and C91.
1.1.1.26 VCC5 OK?
Command VCC5 on by PCLocals. Measure voltage from VCC5 line. If
the voltage is other than 5.00V 50mV go to 1.1.1.27. The delay between
regulator enable and valid voltage at output should be less than 0.1ms.
1.1.1.27 Check N80, C80
Check that CPU enable signal comes to regulator pin 3. If yes try to
disconnect VCC5 load by bending up N80 pin 5 and attaching output
capacitor to the pin. If regulator works after that there is failed ohmic
connection in VCC5 line or in FLASH memories. Otherwise check and
replace N80, C80.
1.1.1.28 VBACK OK?
Measure backup battery voltage from battery terminals. If that is less than
2.8V backup battery is about to be empty in near future (80% used). Then
it is reasonable to change the battery in order to save customer from
inconvenience in near future. In order to do complete test disconnect
main battery from the module. If voltage in VBACK line is under 2.6V go
to 1.1.1.29.
With PC Locals it is possible to check whether the VBACK voltage has
been on illegal level before boot. This can be checked only once after
each boot, and then after the VBACK is considered to be OK.
1.1.1.29 Check G87, V85
Check that voltage over G87 is 2.8V or higher. If not check that there is
maximum 35mV drop over resistor R90. If the drop is higher, RTC
circuitry in VBACK line take too much current. If the drop is OK check that
VBACK line voltage drop in diode V85 is less than 150mV. If not replace
V85.
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After Sales
Technical Documentation
Original, 05/97