FLY DS105 User manual

FLY DS105 Service Menu
Version number:V1.0
2010-07-01
SAGETEL MOBILES (NINGBO) CO.，LTD

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1. The Working Principle of MTK Platform Mobile Phone
This MTK platform mobile consists of the baseband part (MT6223D) and RF part
(transceiver MT6139N and power amplifier SKY77542).
1.1 The Diagram of Mainboard Circuit
(Integrated), Memory, CPU, Keyboard, LCD module, Audio circuit, RF circuit
and etc. As shown in the following figure1:
Figure 1
1.2 The Process of Mobile Phone Power Supply and Power on
1.2.1 The Power Supply Module Part
①VDD，For CPU MN100 and peripheral circuit.
②VCORE 1.8\1.2V，For CPU MN100.
③VM For memory: Flash.
1.2.2 Mobile Power On Process
The process of mobile phone power on\off is mainly driven by Power management、
CPU and memory. While the phone is added cell, VBAT voltage is immediately
produced, and the boot trigger-PWRKEY of the power module is high level. When
the power on or off button is pressed, the voltage of PWRKEY is lowered at once,
generating 26MHz clock. At the same time, VDD、VCORE etc. and Reset Signal (/
SYSRST) is transmitted by the Power Management Module to CPU. After receiving
the system clock、Reset Signal (/ SYSRST) and some logical signal, CPU will run
the power-on program from ROM/RAM. When the mobile is successfully running,
CPU will transmit the message of Boot to maintain the signal. The signal is
received by the Power Module, which maintains all levels of the voltage to achieve
the purpose of the work of the mobile.
1.3 Schematic Diagram of RF Part

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The RF part of the MTK mobile phone consists of MT6139N, Power Amplifier and
Front-end Switch filter module. The RF circuit has two major functions: First,
it receives the selected RF signal from the antenna, demodulates the baseband
signal and then transmits this lower frequency signal to CPU. Second, it
modulates the baseband I, Q signals into the designated RF frequency and
amplifies the power to radiate the signals from the antenna. As shown below:
Figure 2
1.4 Audio Circuit
The received baseband I, Q signals from the antenna, which are modulated into
the data flow，will be mixed-modulated in MA301, amplified, and run GMSK
demodulation. Then the data flow which will be interwoven, decrypted, and
adaptive-equalized, is transmitted into CPU and has the formation at 22.8Kb
/ s. In the information channels, the data flow is decoded and eliminated the
error-correcting code at 9.8Kb / s, in order to get the digital voice signals
at 13Kb / s. Within the CPU, the signals are decoded and reduced into the digital
voice signal at 64Kb / s, which restored into an analog voice signal. After
the voice signal amplified, the receiver makes ourselves heard.
When launching, through the microphone of the acoustic-electric conversion,
the voice signal are transmitted to CPU and amplified to the digital voice signal
at 64Kb/s，which is coded into the digital speech code. After compressed into
the data flow at 13Kb/s and combined with the error correction element on 9.8Kb/s,
and the encryption, interwoven, the signal forms the data flow at 270.833Kb/s.
Then the date flow, which is transmitted into MA301 and carried on the GMSK
modulation, produces the signal IP, IN, QP, QN. At last, the signals are
transmitted into the medium frequency module for launching modulation.

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1.5 Clock Circuit
26MHz Clock Circuit:
With the function of the VCXOEN, the generated 26MHZ clock signal, which is
basic frequency, is transmitted into 21 pin of MA301. One of the signals as
the system clock is transmitted into CPU.
32.768KHZ Clock Circuit:
32.768KHZ Clock which mainly composed of the external crystal Y100, as a
real-time clock signal, is transmitted to CPU for the calculation of real-time
clock.
2. Baseband circuit working principles, common problems and solutions
Baseband circuit mainly consists of the MT6223D chip, the external device
drive circuit, memory storage chips, 32.768KHZ and 26MHZ crystal and so on.
The main peripheral devices are: keyboard interface, SIM card interface, LCD,
FLASH, UART interface and JTAG interface, camera interface, etc.
2.1 SIM card circuit:
Figure 3

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Figure 4
As indicated in Figure 3 is the SIM card interface circuit; Figure 4 is the
dual SIM card dual standby circuit.
If the problem is “SIM card is not inserted”, you can check:
1. the SIM card is damaged;
2. the seat of the SIM card is damaged;
3. the SIM card insertion direction is wrong,
4. SIM card circuit or system main circuit board is failure.
The above items all can lead to “SIM card is not inserted”.
If the first three items is no problem, finally you should check the
SIM card’s signal: SIM_CLK, SIM_IO, SIM_RST and VSIM and the dual card dual
standby selector switches whether the power supply voltage and ground are normal.
If not, replace the chip:sw303.
2.2 MIC、receiver、speaker circle
Mic：

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Figure 5
Receiver：
Figure 6
Speaker：
Figure 7
It’s easy to find such problems as the receiver, speaker is silent or Mic
mute.
It’s usual to dial No *#15963# for us to test whether the phone Receiver is
silent or MIC mute. After entering the test engineering type, there is a function
of “loopback” function to determine this problem. If there are problems during

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the loopback test, it needs to determine the problem between receiver and the
MIC. This can be solved by dialing 112 to judge whether the MIC circuit works
well. If not, it’s the receiver circuit or both have the problem.
receiver circuit
Firstly, you should check whether the receiver circuit is good or not. Second,
if the receiver circuit works well, the first thing is to change the new one
to make sure whether it’s the fault of the receiver; if not, we should consider
it needs to check the CPU, which may have problem or be damaged. It can be solved
through being re-welded or replaced.
MIC circuit
Firstly, you should check whether the receiver circuit is good or not. Second,
if the mic circuit works well, the first thing is to change the new one. However,
if there still has the problem, you should check CPU chip in the same way.
Speaker circuit
If the Speaker can’t work well, at first, it needs to confirm whether the
software setting is in quiet mode or not. If it is not the problem of setting,
you should check whether the speaker circuit works well or not. If the ring
is still not sound, then further inspect audio PA and CPU.
2.3 Keyboard Interface Circuit
The figure8 shows that it’s easy to be invalid for the function of the pressed
key.

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Figure 8
1. firstly, it needs to inspect whether the mobile’s metal demo pastes well
or not;
2. the keypad is dirty or not;
3. However, if there still has the problem, you should check CPU chip
2.4 LCD Interface Circuit
Showing abnormalities usually presents as follows: no display, the un-shining
of the backlight LED, Screen fuzzy or color disorders.
1. During the maintenance, firstly checking the backlight LED
2. Checking LCD module being of a good weld;
3. Checking whether the LCD-related EMI devices have welding problems;
4. Checking whether it is the LCD module issue, please use a good LCD module
to do a replacement test;
5. However, if there still has the problem, you should check CPU chip
Figure 9
2.5 Vibrator Circuit
Figure 10
First we need check whether the contact between the vibrator and the main

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board is good. Then we need check whether the diode(CR502) polarity is correct
and the diode is damaged or not. At last, we adjust the digital power to 2 V,
plus the two control points on the vibrator. If the vibrator do not vibrates,
it illustrates that the vibrator is broken, and replace a new one. If the vibrator
vibrates, it indicates that the control signal has not come to the vibrator.
If the control signal has not been output, we need re-weld or replace the main
chip.
2.6 Un-downloading software
The failure of main board’s proper downloading is mostly due to cold solder
joint or welding. Firstly, the serial port connections between the PC and mobile
phone should be checked. And the fault usually occurs in the pin of the power
management module and connectors I \ O, as well as resistors R516, R517. First
we need look over the welding of these devices with a magnifying glass, then
plug the download cable to see whether the current is normal, if the current
is large (for example, 300mA and above), then there is VCHG or VBAT to ground
short-circuit phenomenon. This time the power should be cut off as soon as
possible, and then find out the short-circuit point. If the current is greater
than the normal value (about 300mA) but not particularly large, there may be
short circuit from the regulator output to ground. And at this time VCORE (1.8V),
VIO (2.8V), VA (2.8V), VTCXO (2.8V), VRTC (1.5V), VMEM (2.8V) and other voltage
should be checked to see if they are normal. If there is an exception, the bad
welding place can be identified. If the current is very small or even no, checking
should be focused on whether the power management module and connectors I \
O is poor welding. In addition, the plug of download wire may cause poor
connections because of long time use. At this time plug the plug again to see
if the problem disappears. While downloading, the 26MHz clock signal is required
apart from the above a number of power supply and the oscilloscope can be used
to test if 26MHz signals are normal. MA301 pin22 should be first checked whether
it has the 26MHz output. If you do not check the MA301 and around the capacitor,
check the voltage input.
The following diagram (Figure 11):
(Note: the measured waveforms are different as
the digital oscilloscope scanning
frequency is different. But the frequency value is of a certain degree.)
Downloading software is mainly the communication between CPU and FLASH,
including the control bus, addresses bus and data bus. If no problems have been
investigated out of the external circuit, and the CPU and FLASH welding are
all well, then the problem may finally lies in the PCB itself, so remove CPU
and FLASH, to check whether the trace is broken or not.

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Figure 11
2.7 Do not power on the mobile
There are four conditions that cell phone can be boot-strapped and work
normally:
i. the properly working of power IC
ii. the correct clock signal
iii.the properly working of logic circuits
iv. the properly running of software
i. The Properly Working of Power IC
a. battery or other power supply needs to provide continual power supply
to the MTK power management IC to make it working properly
b. trigger signal of boot-strap is needed. The power-on trigger signal of
MTK is logical low and goes into the power management IC. It changes from high
to low when you press the power-on key.
c. there are several controllable or uncontrollable regulators integrated
inside the power management IC. When the boot-strap trigger signal goes into
the power management IC, there are several voltages output from the power
management IC.
d. power management IC needs to get the power-on keep going signal which
comes from CPU to generate fixed voltage. Otherwise, the mobile can’t keep
working.
ii. Clock Circuit
Correct system clock is needed. Clock signal provide the basic condition that
it can make CPU disposes data correctly. Generally, 26MHz clock is provided
to CPU by capacitors, resistors or amplifier circuits, and is provided to the
RF’s PLL as the basic clock.
iii. The Properly Working of Logic Circuits
a. proper power supply is needed.
After pressing the power-on button, the power management IC outputs steady