Name: Huawei Ascend G300
Brand: Huawei
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U8815

Maintenance Manual

9 Principles and Failure Analysis

Issue 1.0 (2012-02-13)

Huawei Proprietary and Confidential

Figure 9-49 microSD card connector circuit diagram



Analysis

U1601 is added to prevent electrostatic and for EMI filtering.



Troubleshooting Process

Failure: The microSD card cannot be detected or read.

Solution:

Figure 9-50 shows the troubleshooting process for micorSD card read failure.

Table of Contents4
Product Introduction10
Appearance10
Features10
Figure 1-1 Appearance of the U8815 Handset10
Table 1-1 Description of the Features10
Maintenance Instructions12
Applicable Scope12
Precautions12
Obtaining Product and Maintenance Information12
Exploded View13
Figure 3-1 Exploded View Diagram13
Table 3-1 List of Components in the Exploded View13
PCBA Components15
Figure 4-1 PCBA Components Diagram 115
Figure 4-2 PCBA Components Diagram 216
Figure 4-3 PCBA Components Diagram 317
Figure 4-4 PCBA Components Diagram 417
Software Upgrade18
Upgrade Preparation18
Upgrade Process18
Table 5-1 Upgrade Preparation18
Figure 5-1 Upgrade Process Diagram19
Maintenance Tools20
Table 6-1 List of Maintenance Tools20
Disassembly Procedure22
Assembly Procedure26
Principles and Failure Analysis29
Block Diagram and Handset Introduction29
Figure 9-1 Block Diagram29
Baseband Unit30
Power-On Management Circuits30
Figure 9-2 Power-On Management Circuit Diagram30
Table 9-1 List of Voltages Converted from VHP_PWR by PM8029 Power Management Chip32
Figure 9-3 Troubleshooting Process for no Current33
Figure 9-4 Troubleshooting Process for Weak Current34
Charging Management Circuits35
Figure 9-5 Troubleshooting Process for High Current35
Figure 9-6 Charging Management Circuit Diagram 136
Figure 9-7 Charging Management Circuit Diagram 236
Figure 9-8 Charging Management Circuit Diagram 336
Figure 9-9 Charging Management Circuit Diagram 437
Figure 9-10 Troubleshooting Process for Charging Failures38
Clock Circuit39
Figure 9-11 19.2 Mhz Circuit Block Diagram 139
Table 9-2 Description of the Signals in the Circuit Diagram in this Section39
Figure 9-12 19.2 Mhz Circuit Block Diagram 240
Figure 9-13 32.768 Khz Circuit Block Diagram 140
Figure 9-14 Analysis of Clock Circuit40
Flash Memory Circuit41
Figure 9-15 Flash Memory Circuit Diagram 142
Figure 9-16 Flash Memory Circuit Diagram 242
Figure 9-17 Flash Memory Circuit Diagram 343
Figure 9-18 Flash Memory Circuit Diagram 444
Figure 9-19 Analysis of the U8815 Memory Interface45
Table 9-3 Description of the Signals in the Circuit Diagram in this Section45
RF Unit46
Figure 9-20 Transmitting and Receiving Circuit Block Diagram46
Power Amplifier47
Figure 9-21 WCDMA IMT PA Diagram47
Table 9-5 Logic Table of the RF Switch47
Figure 9-22 WCDMA 850 PA Diagram48
Figure 9-23 WCDMA PCS PA Diagram48
Figure 9-24 GSM Quad_Band_Pa Diagram48
Troubleshooting49
Figure 9-25 UMTS IMT RX INTERSTAGE CHAIN Diagram49
Figure 9-26 Diagram of Dualband RF Transmitting and Receiving by Using RTR6285A Chip49
Figure 9-27 Troubleshooting Process for Receiving Failure50
Table 9-6 Truths for Control Signals51
Figure 9-28 Troubleshooting Process for Transmission Failure52
Peripheral Circuits53
Display Screen53
Figure 9-29 Display Screen Circuit Diagram 154
Figure 9-30 Display Screen Circuit Diagram 254
Figure 9-31 Display Screen Circuit Diagram 355
Figure 9-32 Troubleshooting Process for no LCD Display56
Table 9-4 Description of the Signals in the Circuit Diagram in this Section56
Table 9-8 Description of the Signals in the Circuit Diagram in this Section56
Vibration57
Figure 9-33 Motor Circuit Diagram57
Call Reception58
Figure 9-34 Vibration Maintenance Process58
Table 9-9 Description of the Signals in the Circuit Diagram in this Section58
Figure 9-35 Call Reception Circuit Diagram 159
Figure 9-36 Call Reception Circuit Diagram 259
Figure 9-37 Call Reception Circuit Diagram 359
Figure 9-38 Call Reception Circuit Diagram 460
Figure 9-39 7227A Audio Processing Diagram60
Table 9-10 Audio Output61
Call Transmission62
Figure 9-40 Troubleshooting Process for Sound Failure62
Figure 9-41 Primary Handset Microphone Circuit Diagram63
Figure 9-42 Secondary Handset Microphone Circuit Diagram64
Figure 9-43 Troubleshooting Process for Sound Failure65
Table 9-11 Description of the Signals in the Circuit Diagram in this Section65
Headset66
Figure 9-44 Headset Circuit Block Diagram66
Figure 9-45 Troubleshooting Process for no Sound from the Headset Failure67
Table 9-12 Description of the Signals in the Circuit Diagram in this Section67
SIM Card68
Figure 9-46 SIM Card Circuit Diagram68
I/O Connector69
Figure 9-47 Troubleshooting Process for the UIM Card Detection Failure69
Table 9-7 Description of the Signals in the Circuit Diagram in this Section69
Table 9-13 Description of the Signals in the Circuit Diagram in this Section69
Microsd Card Connector70
Figure 9-48 I/O Connector Circuit Diagram70
Table 9-14 Description of the Signals in the Circuit Diagram in this Section70
Figure 9-49 Microsd Card Connector Circuit Diagram71
Figure 9-50 Troubleshooting Process for Micorsd Card Read Failure72
Figure 9-51 FM Circuit Diagram 172
Figure 9-52 FM Circuit Diagram 273
Figure 9-53 FM Circuit Diagram 373
Figure 9-54 Troubleshooting Process for FM Radio Failure74
Table 9-15 Description of the Signals in the Circuit Diagram in this Section74
Solder Points on the PCB and BGA Chip75
Figure 10-1 Diagram 1 of the Solder Points on the PCB and BGA Chip75
Figure 10-2 Diagram 2 of the Solder Points on the PCB and BGA Chip76
Figure 10-3 Diagram 3 of the Solder Points on the PCB and BGA Chip76
Figure 10-4 Diagram 4 of the Solder Points on the PCB and BGA Chip77
Performance Test78
Keys78
Figure 11-1 U8815 Handset Key78
MMI Test79
Voice Call Test80

Brand	Huawei
Model	Ascend G300
Category	Cell Phone
Language	English

Huawei Ascend G300 Maintenance Manual

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