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FS501 Service Manual
V1.0
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Contents
1. FS501 key features ............................................................................................................... 3
1.1 FS501 brief introduction ..................................................................................................... 3
1.2 Function diagram ................................................................................................................ 4
1.3 Mainboard component distribution diagram ....................................................................... 5
1.4 Main IC Names ................................................................................................................... 7
2. RF ......................................................................................................................................... 8
2.1 WCDMA RF power trouble ................................................................................................ 8
2.2 GSM RF power trouble........................................................................................................9
2.3 WCDMA RX trouble ........................................................................................................ 11
2.4 GSM RX trouble ............................................................................................................... 12
2.5 WiFi/BT/BT Part ............................................................................................................. 14
3. Baseband section .................................................................................................................. 7
3.1 Outline .............................................................................................................................. 16
3.2 Common Failure Analysis and Maintenance .................................................................... 17
3.2.1 Power failure Check .............................................................................................. 17
3.2.2 Audio faults ........................................................................................................... 18
3.2.3 LCD Fault .............................................................................................................. 22
3.2.4 FM ......................................................................................................................... 23
3.2.5 Camera fault ................................................................................................................... 24
3.2.6 SIM card failure .................................................................................................... 25
3.2.7Motor test is invalid ...................................... Ошибка! Закладка не определена.
3.2.8 Gravity Sensor ....................................................................................................... 26
3.2.9 T-Flash fault........................................................................................................... 27
3.2.10Touch Panel function ............................................................................................ 27
3.2.11 Cannot boot failure .............................................................................................. 28
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1. FS501 key features
1.1 FS501 brief introduction
The development and design of the FS501 PCBA is based on SC7731G platform. The mainboard system mainly
consists of the chip SC7731G+SR2351C +SR3131, which are responsible for three part functions, namely, baseband,
radio frequency and GPS/WIFI/BLUETOOTH/FM chip. FS501 PCBA is an all-in-one phone mainboard, which supports
GSM, WCDMA, and covers Bluetooth, WIFI, GPS, Camera, FM functions, and so forth.
The maintenance of mainboard is one of the important links among mobile products rear-end producing. The
speed and quality of maintenance relate to the rate of good products, production efficiency, and cost control
throughout the producing. In the case of a reasonable design of product, in the end-producing, finding the significant
proportion in the bad board should be SMT bad and component incoming material bad. So, when maintaining, first,
start with the two aspects. The principal means of fault diagnosis are: (1) find that bad welding spots or components
by microscopic examination and visual inspection; (2) guess failure positions from the fault phenomena; (3) confirm
the fault units by signal detection.
1.2 Function diagram
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1.3 Mainboard component distribution diagram
Mainboard TOP
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Mainboard BOTTOM
1.4 Main IC Names
Num
ber
Name
Product model
location
1
SC7731G;SC7731G;597;FCVFBGA;13.3X12.1;040;BB
;WCDMA
SC7731G
U0100
2
MEM,P-VFBGA162,4GB/4Gb,6/1.9nS,e-
MMC/LPDDR2,4Gbx8/128Mx32,1.8V/3.3V,MCP,1.8/1
.2V,13*11.5*1.0
TYC0FH121638RA
U0500
4
SR2351C;38;QFN;5.5x4.5;040;RF
SR2351C
U801
5
SR2319A;16;QFN;2.5*2.5;050;
SR2319A
U803
6
SAW滤波器-1575.42MHZ-0.9DB-1.4*1.1*0.6
SAFEB1G57KE0F00
U805
U806
7
LNA;GPS/GNSS;1x1.5x0.75mm
MXDLN16G
U807
9
XTL,TCXO,SMT,26.000MHz,0.5PPM
1.8V,2.5x2x0.8mm
NT2520SB-ENG3216E
Y801
10
Multilayer Chip Band-Pass Filters -2.4GHz
BF2012-L2R4-NBA-
T/LF
U808
11
SR3131;50;QFN; 5.5x7; 040; RF; 3G
transceiver
SR3131
U901
12
SAW FILTER FOR GSM900 (Rx)
SAFEA942MFL0F00R1
4
Z901
13
SAW FILTER FOR GSM1800/GSM1900 (Rx)
SAWEN1G84CV0F00
Z907
14
PA QuadBand GSM/GPRS and Dual-Band WCDMA
Handsets
• LGA 6mm x6mm x0.9mm
SC2662H
U902
15
PA Module for
WCDMA/HSDPA/HSUPA/HSPA+Application
• 3mm*3mm*0.9mm
SC2671H
U903
PA Module for
WCDMA/HSDPA/HSUPA/HSPA+Application
• 3mm*3mm*0.9mm
SC2678H
U905
FLT,DUPLEXER,SMT,925/960MHz,882.4/912.6MHz,2
x1.6x0.55mm 2.5dB,1.5dB,UMTS?BAND8
SAYFH897MHC0F0A
U906
16
SAW DUPLEXER FOR UMTS BC1
SAYRF1G95HQ0F0A
U904
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2.1 WCDMA RF power trouble
Check points
-PA connector soldering
-Duplexer connector soldering
-Other Tx RF Component soldering
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Wcdma Band I
Wcdma Band VIII
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Start
Replace PA
Check PA
connector
soldering is ok?
Yes
Check Dupolexer
connector is ok?
No
Resoldering
No
Resoldering
Yes
Check Other Tx RF
components
soldering is ok?
No
Resoldering
2.2 GSM RF power trouble
Check points
-Tranceiver connector soldering
-PA connector soldering
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