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W420 use SMT motor pasted on the main board. SMT motor is propitious to mass production, and
connect with main board well, provide optimal shake effect. Drive voltage of Motor is provided by VBAT. The
use of Motor can be controlled by FADD19 in the system: source pole and drip pole of Q750 will connect when
FADD19 is set at high level, then the Vibrator begin to work; source pole and drip pole cut off when FADD19 is
set at low level, then Vibrator stop working. Resistance R751 and R752 are use to limit current when Vibrator
working
8. Frequently malfunction analyse
It is needed to connect TP38, TP39 and TP2, TP3. USB line should add VBAT and GND. BlueTooth should
pass two path that both MPU-RX and MPR-TX1, connect to BASEBAND, add VBAT and GND.
8.1: Can not download program
1. First check U201 and U307, is there weld connective or weld weakly between them
2. Check voltage, 5V at VCUSB, 1.2V at USB-VM in U201, 1.8V at USB-VP. Check R416A, R146B,
R330, R331, R334 normal or not and if U420 disabled when the voltage above getting normal. If all of them
getting normal, then weld U201 again.
8.2: Can not turn on
1. Check battery. If the battery voltage is under 3.5V, then it is needed to charge. On the contray, it may
be connect weakly between battery and battery seat
2. Check if there is weld weakly on the battery seat
3. Check U201, U202, U603, U402 and the resistances and capacitance around, is them weld weakly or
excursion, and is there weld connective on PCB board
4. Connect an external power source (set at 3.8V) to +/- pole of the battery seat. If there is current
passing the powermeter before ON, it is illuminated that the mobile is creepaged. Check voltage for power
supply LDO when turn on the mobile, the voltage value of U309 (V-IO-2), U301(V-MEMORY), U303 (V-CORD)
should be 2.8V, 1.8V, 1.5V respectively. Check creepaged or not after extirpating the abnormal one
5. Check VRUSB, if there is no voltage on it or abnormol with it, then the malfunction may be at U202
6. Check V-SIM, if there is no voltage on it or abnormol with it, then the malfunction may be at U202
7. Check V-RTC, if there is no voltage on it or abnormol with it, then the malfunction may be at U202
8. Check V-IO, if there is no voltage on it or abnormol with it, then the malfunction may be at U202
9. Check VABB, if there is no voltage on it or abnormol with it, then the malfunction may be at U202
10. Check 26MHz clock output, if it is normal, may be malfunction is caused by U202
11. Measure 32.768 clock, check C201, C203, C204, R212, if all of them getting normal, may be
malfunction is caused by U202
12. Validate download software normal or not again
8.3: No display, No background light
1. Check connection between main board and LCD. Refix it if the connection failed
2. Install a new LCD instead of the old one. If it getting normal, then the old one must be damaged
3. Check the pin of the connector. Reweld if there is weld connective or weakly
Summary of Contents for W420
Page 1: ...Voxtel Repair Manual Item W420 ...
Page 23: ...23 3 LDO circuit ...
