All Common Problem Solution For China Phone

Subject: All Common Problem Solution For China Phone Sat Oct 23, 2010 7:46 pm

All Common Problem Solution For China Phone

First we need to know why a phone is dead-
1. For Software
2. For Hardware

1. For Software-
Flash is its final solution, but mtk cpu 90% phone done by format. if its MTK,SPD,AD, SI4904 cpu first try to format than try to full flash your phone with a good and perfect flash file. and other cpu haven't format option, so direct flash them. when you flash careful about original flash file version.

A. what you do before format or flash-
Always remember, before format or flash of your any china phone must first backup your current flash file if phone is dead, also do it. because it will help to find its original flash file version and many other.

B. What you need for flash or format a china phone-
(1) Connecting device (also your can do it with usb to serial cable but a device/box can give you full/final solution)
(2) Phone TX and RX.
(3) Need to know phone cpu type/model, flash chip type/model, Flash file version.
(4) For Flash need a good flash file which same to your phone original flash file version.

C. What problem you face for wrong flash file
(1) phone still dead
(2) white screen
(3) keypad not work
(4) phone hang after power on
(5) keep restarting
(6) no network
(7) etc.

Tool For MTK Flash info

2. For Hardware-
when a dead phone not possible to repair only with software you need to repair phone hardware.

Which hardware you need to check for dead phone-
(1) when you try to flash if phone not boot check power source/battery voltage/V+ pin in phone connector. just do confirm phone found enough voltage for software operation.
(2) if phone power source is ok but still not boot, do confirm your tx and rx is 100% working/tested.
(3) if tx rx is ok, than check your phone connector, its tx rx pin is confirm connect with cable and internal connector pin is joint on pcb perfectly.
(4) if pin is ok, maximum china phone tx rx going to cpu after crossing a resistor or capacitor so check them.
(5) if resistor is ok now you need to check boot diod, all phone have no boot diod so last try is check cpu tx rx pin.
(6) if boot is ok but phone not receive flash file, maximum time this problem coming from flash ic or ram (maximum china phone flash memory and ram have in one chip). so you need to try first re-hot it if still not solve change it.
but its true flash chip/ram always show error not only for them, sometimes cpu to flash chip/ram connection lost for bad cpu pin or bad cpu soldering on pcb. so check both of them.
(7) phone flash ok but not power on (although file is 100% correct) , for it you need to check

Flash chip/ram (95% include in 1 chip)
Clock crystal and battery
26mhz (near rf ic)
Rf ic,
Power ic and v+/b+ way
Bt ic
Last try is cpu.

How to repair keypad problem in china phone-

First we need to know china phone keypad connected with PCB how way-

(A) Direct on PCB

(B) Flex System (flex cable direct soldering pcb to keypad panel)

(C) Flex and socket system include (flex one side soldering with key panel other side connect to pcb with socket)

(D) only Socket System (here have 2 socket, 1 with key panel others with pcb)

Keypad problem have various type-

1. All key not work.

2. some key work and some other not work.

3. sometimes work and sometimes not work.

1. All key not work
china phone all key not work for this type of problem-

(A) though its touch screen phone, first try to disconnect touch panel line from phone pcb or display flex (4 line)

(B) though not solve and keypad direct on pcb first you try to good clean full pcb with cleaner.

(C) though not solve now you try to format/flash your phone because some time key problem come from software problem.

(D) though still not solve now you check must be CPU. 95% china phone keypad directly going in cpu. and other 5% first going to resistor or capacitor near the cpu or keypad than going to cpu. so now first check them than you can try to re-hot, re-soldering or changing cpu.

(E) though its flex or socket system, first check GND connection continuslay pcb to key panel. next check full flex or socket all line going continuously pcb to key panel or not. also sometimes flex or socket shorted with other line or gnd so check also them.

(F) Also you can check all key anyone is short 2 line.

(G) sometimes keypad line broken from cpu pin on pcb to key panel, so check them.

2. Some key work and some other not work-
Some key work and some other is not work for this type of problem-

(A) maximum time this problem we face for flex or socket system keypad. so check flex cable and socket all line any line is broken or not and though need change them. and check all key connection on key panel.

(B) though its direact on pcb, some of key line broken internaly. and maximum china phone have alternative test point near every key or with other key on keypad. so check them with multimeter and though need connect to not work key with near testpoint or other working key.

(C) common problem is keypad metal ball (which is short 2 line on key when we press) sometimes its damage for phone water damage or over key voltage, so clean them or change.

(D) also try to check line continuously from cpu to not working key.

3. sometimes work and sometimes not work-
this problem come from this defect-

(A) flex or socket system keypad any line is bad soldering or do lose contact. check them and
re-soldering or keep there line join with extra ware.

(B) for cpu bad soldering or cpu pin is broken. so re-hot or re-ball cpu.

I post here keypad common problem solution, hope it will help you to fixing your keypad problem
Reply

Method 1:

HOW TO FIND RX TX

It is tasted and also you can test it.

1 step is, we need to find GND from phone.

2 step is, we should power on phone (operation with dead phone:
phone must be 100% dead by software)and take multimater put it to voltage.

3 multimeter (-) line put it GND and with (+) line check each connectors
, and usually Tx= 1.8v or 2.8v and Rx=1.7v or 2.7v
(it will be change by processor but strongly 1.7v or 2.8v not 3v or 4v)
This way is too easy and you will save a more time.

Method 2:

How To Find Rx,Tx "The Multimeter Method"

1. Plug your new connector into your phone, with solder pads/pins exposed
2. Put Multimeter into fault-check. (or if unavailable, then it’s highest resistance range)
3. Keep negative Multimeter probe on negative battery connector in phone.
4. Touch each pin of the connector in sequence with the other probe until you hear a beep ( or see 0.000 resistance )
5. Note this connector pin as GNDPin
6. Now install battery and switch on Phone
7. Put Multimeter into DC voltage measurement
8. Keep negative Multimeter probe on GNDPin
9. Touch other pins of the connector in sequence and note pins that have voltage between 2.6 and 2.9 volts.(be careful not to short pins )
10. You should end up with a list of 2 or 3 pins. RX and TX will be among these.
11. Try all combinations of RX and TX with these pins you found.

I’ve found several hundred pinouts with the method above. It works 99% of the time, and takes about 2 minutes once you’re in practice.
So you now have your RX, TX, GND wires on your interface end, and your pinout or set of pinouts to try for the phone.

How to find out same display for your china phone-

maximum time we face problem for changing display for china phone, they all are not available
in market, so we collect them from other same china phone.

now problem is when we collect display from other same phone how we understood about this
display version or model.

plz see picture below-

All Common Problem Solution For China Phone Displa10

All Common Problem Solution For China Phone Displa10

here have 3 display, there size same and collect from same model phone, but here 2 display is similes but 1 is not same to other.

so, now i think every member understood how can he get his display version from see display.

its remember always- sometimes changing same display from same phone, we can't success for this- you must check phone software/ flash file version. because maximum time display working depend on software version. so don't worry. try to update you flash file, which have in collected display phone. and don't forgate to backup your current flash file before flash with new file.

Sometimes display same not available in market what can we do just see the leg & light direction of dislay where is going light connection other wise match the display see Image

All Common Problem Solution For China Phone Ffffff10

All Common Problem Solution For China Phone Ffffff10

Posts : 5 Join date : 2011-01-30 Age : 39

thx sir...........
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