EivoTech Laptop & Mobile Repair Master Course
Part 14 — LAN, Wi-Fi, Bluetooth aur Network Circuit Complete Mastery
Chapter 14: CPU/PCH se Ethernet, Wi-Fi aur Antenna Tak Complete Network System
Laptop network faults common hain:
LAN cable detect nahi hoti
Ethernet device Device Manager mein missing
Cable connected hai lekin link LED nahi
Wi-Fi option hi nahi aa raha
Wi-Fi card detect nahi hoti
Bluetooth missing hai
Wi-Fi works but Bluetooth nahi
Bluetooth works but Wi-Fi weak hai
Signal bohat weak hai
Wi-Fi disconnect hoti rehti hai
Airplane mode stuck hai
Ek antenna wire broken hai
M.2 Wi-Fi slot dead hai
In faults ko diagnose karne ke liye humein pehle samajhna hoga:
LAN aur Wi-Fi same system nahi hain.
1. Network Kya Hai?
Network ka matlab devices ke darmiyan data communication.
Laptop commonly network connect karta hai:
Ethernet / LAN
ya
Wi-Fi
Bluetooth bhi wireless communication hai, lekin internet networking se alag short-range protocol hai.
2. LAN Kya Hai?
LAN:
Local Area Network
Laptop mein wired Ethernet connection ke liye commonly:
RJ45 port
use hota hai.
Ethernet cable:
Laptop
↓
Router / Switch
ko physically connect karti hai.
3. Ethernet ka Basic Flow
Simplified:
CPU / PCH / SoC
↓
LAN Controller / PHY
↓
Magnetics / Transformer
↓
RJ45 Connector
↓
Ethernet Cable
↓
Router / Switch
4. MAC aur PHY Kya Hain?
Ethernet architecture mein do important concepts:
MAC
aur
PHY
5. MAC
MAC:
Media Access Control
Network data frames ko manage karta hai.
MAC function:
PCH/SoC ke andar integrated ho sakta hai
ya dedicated LAN controller ka part ho sakta hai.
6. PHY
PHY:
Physical Layer Transceiver
Digital controller aur actual Ethernet cable electrical signals ke darmiyan interface karta hai.
Simple language:
PHY Ethernet signal ko cable ke suitable electrical form mein convert karta hai.
7. Dedicated LAN Controller
Laptop motherboard par dedicated Ethernet controller IC ho sakta hai.
Common manufacturers:
Realtek
Intel
Broadcom
Marvell
etc.
Some systems mein MAC platform ke andar aur PHY external hota hai.
8. LAN Controller ko Kya Chahiye?
Typical requirements:
Power rails
Ground
Clock
Reset
PCIe/other host communication
EEPROM/firmware/configuration depending design
Ethernet magnetics
9. LAN Controller Power Rails
Possible:
3.3V
1.8V
1.0V / core rail
other internal LDO outputs
Exact chip-specific.
Agar device system mein missing:
Power rails first check.
10. LAN Controller VCC Missing
Possible:
3.3V source missing
Ferrite bead open
LDO disabled
Load switch fault
Shorted capacitor
LAN IC short
11. LAN Controller Reset
Signal names:
LAN_RST#
PCIE_RST#
PERST#
etc.
Agar controller reset mein held hai:
Device enumerate nahi karega.
12. LAN Controller Clock
Depending design:
25MHz crystal
PCIe reference clock
other oscillator
use ho sakta hai.
Clock missing:
LAN device detect nahi ho sakta.
13. PHY Crystal
Ethernet PHY ke paas common:
25 MHz crystal
mil sakta hai.
Exact frequency/controller-specific.
Multimeter se proper clock verify nahi hoti.
Oscilloscope useful.
14. LAN Controller Device Manager mein Missing
Possible:
Controller power missing
Reset missing
Clock missing
PCIe link problem
LAN IC faulty
BIOS disabled
Driver issue
15. LAN Device Present but Cable Detect Nahi
Agar Device Manager mein Ethernet adapter present hai:
Controller platform se communicate kar raha.
Focus:
PHY analog side
RJ45 port
Magnetics
Cable
Transformer
Connector pins
16. RJ45 Connector
RJ45 Ethernet connector mein:
Multiple signal pins
Link/activity LEDs
Shield
ho sakte hain.
Some laptop connectors collapsible/hinged type bhi hote hain.
17. LAN Link LED
Cable connect karne par:
Link LED ON/blink
useful clue hai.
Agar:
Device detected
but no link LED
then cable/PHY/magnetics/RJ45 side inspect karo.
18. Magnetics Kya Hain?
Ethernet cable aur PHY ke darmiyan:
Isolation transformer / magnetics
use hoti hain.
Purpose:
Electrical isolation
Signal coupling
Noise rejection
Common-mode filtering
19. Magnetics Kahan Hoti Hain?
Possible:
Separate transformer module
ya
RJ45 connector ke andar integrated magnetics
ho sakti hain.
20. Transformer Fault
Possible:
No link
One speed only
Intermittent LAN
One pair open
Data errors
21. Ethernet Differential Pairs
Ethernet high-speed differential pairs use karta hai.
Different Ethernet standards multiple twisted pairs use karte hain.
Signal lines ko random voltage apply nahi karna.
22. 100 Mbps vs 1 Gbps
Gigabit Ethernet more pairs use karta hai compared with older 10/100 implementations.
If one pair/path damaged:
System sometimes lower speed par negotiate kar sakta hai
ya link completely fail.
23. Ethernet Cable Connected but Internet Nahi
Ye hardware fault zaroori nahi.
Possible:
Router issue
IP configuration
DNS
Driver
Cable
No DHCP
ISP issue
Isliye first check:
Link present?
Adapter detected?
IP mila?
24. LAN Hardware vs Internet Problem
Hardware side:
Adapter missing
No link light
Cable not detected
Network/software side:
Link hai
IP issue
Internet nahi
DNS problem
Router problem
25. Known-Good Cable
LAN diagnosis mein known-good Ethernet cable bohat useful hai.
Bad cable se motherboard fault jaisa symptom aa sakta hai.
26. RJ45 Physical Inspection
Check:
Bent contacts
Broken locking section
Corrosion
Liquid damage
Damaged LEDs
Cracked solder
Connector movement
27. Liquid Damage Near LAN Port
RJ45 external opening hai.
Liquid/corrosion affect kar sakti hai:
Magnetics
ESD protection
PHY lines
LED circuits
Controller
28. LAN ESD Protection
Ethernet connector external world se connected hota hai.
Protection devices ho sakte hain.
ESD component fault:
One differential pair short
No link
Intermittent link
29. LAN Controller PCIe Interface
Many dedicated LAN controllers host se:
PCIe
through connect hote hain.
Requirements:
3.3V power
PERST#
REFCLK
PCIe TX/RX
similar to NVMe architecture.
30. LAN Device Missing but Power Present
Check:
PERST#
REFCLK
PCIe lines
BIOS settings
Controller
31. Ethernet MAC Address
Network adapter ka unique logical hardware address:
MAC address
hota hai.
Firmware/EEPROM/configuration se related ho sakta hai.
Wrong firmware/configuration:
Invalid/missing MAC possible.
32. LAN EEPROM
Some LAN designs separate EEPROM/flash use karte hain.
Stores:
Configuration
MAC
Device settings
Firmware info
Exact architecture chip-specific.
33. Wi-Fi Kya Hai?
Wi-Fi wireless network connection hai.
Laptop radio waves ke through router/access point se communicate karta hai.
34. Wi-Fi System ka Basic Flow
Simplified:
CPU/PCH/SoC
↓
PCIe / CNVi / Other Interface
↓
Wi-Fi Card
↓
RF Section
↓
Antenna Cables
↓
Laptop Antennas
↓
Router
35. Wi-Fi Card Types
Laptop mein:
Mini PCIe
M.2
Soldered Wi-Fi
CNVi/CNVio type modules
mil sakte hain.
Modern laptops mein M.2 common.
36. M.2 Wi-Fi Card
Usually small M.2 card.
Commonly 2230 size.
Card par tiny coax antenna connectors hote hain.
37. Wi-Fi M.2 Keying
Wi-Fi cards commonly:
A-Key
E-Key
A+E Key
type connectors use kar sakti hain.
SSD M.2 slot se different wiring.
38. Wi-Fi Card ko Power
Commonly:
3.3V
supply hoti hai.
Exact module/platform se confirm karo.
39. Wi-Fi Power Missing
Possible:
3.3V rail missing
Fuse
Load switch
WLAN enable
Slot damage
Card short
40. WLAN_EN
Wi-Fi card ko enable signal mil sakta hai.
Names:
WLAN_EN
WL_EN
W_DISABLE#
RF_KILL#
platform-specific.
41. W_DISABLE#
Common concept:
Wireless disable control.
Active-low implementation possible.
If wrong state:
Wi-Fi radio disabled reh sakta hai despite card detected.
42. Airplane Mode
Airplane mode software + hardware control dono involve kar sakta hai.
Possible inputs:
Keyboard hotkey
EC
Wireless disable signal
OS setting
Wi-Fi driver
43. Wi-Fi Card Device Manager mein Missing
Check:
Correct card
3.3V
Slot contacts
Reset
PCIe/CNVi interface
BIOS
Driver
Card itself
44. Wi-Fi Card Detect hai but Networks Nahi Dikhte
Possible:
Antennas disconnected
RF radio disabled
Driver
Country/regulatory config
Card RF section fault
Airplane mode
45. Weak Wi-Fi Signal
Strong suspects:
Antenna cable loose
Antenna connector damaged
One antenna wire broken
Antenna foil/module damaged
RF connector broken
Card fault
46. Antenna System
Laptop antennas usually display lid ke andar hoti hain.
Reason:
Better RF position
Less motherboard shielding
More physical antenna area
47. Antenna Coax Cable
Wi-Fi card se antenna tak tiny coaxial cables jati hain.
Usually labels:
MAIN
AUX
1
2
etc.
48. MAIN aur AUX
Wi-Fi cards often multiple antennas use karte hain.
Purpose:
MIMO
Diversity
Higher speed
Better signal
49. One Antenna Disconnect
Possible:
Wi-Fi still works
but range/speed reduced.
Bluetooth performance bhi affect ho sakti hai depending card/antenna architecture.
50. Both Antennas Disconnect
Laptop nearby router detect kar sakta hai.
Lekin range bohat weak.
This can look like bad Wi-Fi card.
51. Antenna Connector Damage
Tiny snap-on connector bohat delicate.
Wrong pressure:
Socket card se rip ho sakta hai.
Coax connector damage ho sakta hai.
Magnification use karo.
52. Antenna Wire ko Normal Wire se Replace?
RF coax controlled impedance use karta hai.
Random normal wire proper high-frequency replacement nahi.
Correct coax/antenna assembly use karo.
53. Wi-Fi MIMO
MIMO:
Multiple Input Multiple Output
Multiple antennas/data streams use karke speed/reliability improve hoti hai.
Example:
1x1
2x2
configurations.
54. Wi-Fi Bands
Common Wi-Fi frequencies:
2.4 GHz
5 GHz
6 GHz on supported newer Wi-Fi systems
Card + antenna + router + regulatory support required.
55. 2.4 GHz Works, 5 GHz Doesn't
Possible:
Card capability
Driver/settings
Router issue
Antenna/RF path
Card RF chain fault
Not always motherboard power fault.
56. Bluetooth Kya Hai?
Bluetooth short-range wireless communication protocol hai.
Use:
Mouse
Keyboard
Headphones
Phone
File/device communication
57. Wi-Fi + Bluetooth Combo Card
Modern laptop card often:
Wi-Fi
Bluetooth
same physical module mein hoti hai.
Important:
Dono host se same interface necessarily use nahi karte.
58. Wi-Fi aur Bluetooth Interface Difference
Common architecture:
Wi-Fi → PCIe/CNVi
Bluetooth → USB
Yani same card par Wi-Fi work kar sakta hai lekin Bluetooth fail.
59. Wi-Fi Works, Bluetooth Missing
Strong direction:
Bluetooth USB path
BT enable
Driver
Card internal BT section
USB data lines
BIOS
60. Bluetooth Works, Wi-Fi Missing
Focus:
Wi-Fi PCIe/CNVi side
WLAN enable
Card RF section
Driver
61. Bluetooth USB Lines
Combo card ke Bluetooth section ko:
USB D+
USB D-
signals mil sakte hain.
If these lines damaged:
Wi-Fi still work.
Bluetooth missing.
62. Bluetooth Power
Bluetooth module same 3.3V supply share kar sakta hai.
Ya internal regulator use kar sakta hai.
If entire card powered and Wi-Fi works:
Main power likely okay.
63. Bluetooth Device Manager mein Missing
Check:
Wi-Fi card detected?
If yes:
BT USB interface.
Driver.
USB path.
Card itself.
64. CNVi / CNVio Kya Hai?
Certain Intel platforms mein some Wi-Fi functions CPU/PCH side par integrated hote hain.
Module fully independent PCIe Wi-Fi card jaisa nahi hota.
This architecture:
CNVi/CNVio family
kehlati hai.
65. Wrong Wi-Fi Card Compatibility
Physical M.2 fit hone ka matlab compatible hona nahi.
Laptop/platform may require:
PCIe card
CNVi card
specific generation
BIOS support
Different module insert karne par detect nahi hogi.
66. BIOS Wireless Whitelist
Kuch older laptop manufacturers certain approved Wi-Fi cards restrict karte the.
Unsupported card par BIOS warning/no boot possible.
Modern behavior manufacturer-specific.
67. Wi-Fi Card PERST#
PCIe-style Wi-Fi card reset:
PERST#
use kar sakti hai.
If stuck low:
Wi-Fi PCIe section enumerate nahi karega.
68. Wi-Fi REFCLK
PCIe Wi-Fi interface ko reference clock required ho sakta hai.
No clock:
Card detect fail.
Oscilloscope advanced diagnosis.
69. Wi-Fi CLKREQ#
Card power management ke liye clock request signal use kar sakti hai.
Same PCIe concepts Part 11 se apply hote hain.
70. Wi-Fi Slot Short
Bad card 3.3V rail short kar sakti hai.
Symptoms:
Wi-Fi rail collapse
Laptop power issue in some designs
Card heating
Remove card and compare rail.
71. Card Hot
Wi-Fi card slight warm normal ho sakti hai.
Immediately very hot + no detection:
Internal short possible.
Test known-good compatible module.
72. Wi-Fi Card Known-Good Test
One of best tests:
Known-good compatible card.
If new card works:
Old card fault.
If same failure:
Motherboard slot/power/interface.
73. Wi-Fi Option Missing in Windows
First differentiate:
Device Manager mein card present?
Present
Driver/software/radio state.
Missing
Hardware/BIOS/interface.
74. Wi-Fi Device Disabled in Device Manager
Could be:
Driver
OS
manual disable
power-management setting
not necessarily board issue.
75. BIOS mein WLAN Disabled
Many business laptops allow:
WLAN
Bluetooth
LAN
disable settings.
Check before hardware repair.
76. Airplane Mode Stuck
Possible:
Windows setting
Hotkey driver
EC input
RF kill switch
WLAN disable signal
Wi-Fi card fault
77. Physical Wireless Switch
Older laptops sometimes physical Wi-Fi switch use karte hain.
Broken switch can hold wireless disable state.
78. Keyboard Wi-Fi Hotkey
Modern laptops:
Fn key/hotkey.
EC detects input.
OS/firmware toggles wireless state.
Hotkey issue ≠ Wi-Fi hardware fault necessarily.
79. Wi-Fi Antenna Continuity
Antenna coax ko normal DC continuity test limited information deta hai.
RF performance only continuity se prove nahi hoti.
Damaged coax physically inspect/replace.
80. Antenna Connector Center Pin
Coax connector:
Center conductor
Outer shield/ground
use karta hai.
Center conductor open:
Signal weak/no RF.
Outer shield damage:
Noise/performance issue.
81. Antenna Cables Crossed
MAIN/AUX cables wrong ports par lagne se system often still work kar sakta hai.
But manufacturer routing follow karna best hai.
Some cards/antenna arrangements performance-specific hote hain.
82. Wi-Fi Signal Strong but Internet Slow
Could be:
Router congestion
ISP
Channel interference
Driver
Power saving
Network configuration
Not motherboard RF issue automatically.
83. Wi-Fi Disconnects Randomly
Possible:
Weak antenna connector
Card overheating
Driver
Power saving
Router issue
3.3V instability
Slot contact
84. Wi-Fi Works Near Router Only
Strong suspicion:
Antenna not connected
Damaged antenna
RF front-end/card fault
85. Bluetooth Range Very Short
Possible:
Antenna issue
Card RF section
Interference
Device issue
Depending combo-card antenna sharing.
86. LAN Works but Wi-Fi Dead
Wired and wireless paths separate.
LAN working does not prove PCH wireless/PCIe slot healthy.
87. Wi-Fi Works but LAN Dead
Same rule.
Focus LAN controller/PHY/RJ45.
88. LAN Device Present, No Link
Diagnostic flow:
Known-good cable
↓
Known-good router port
↓
RJ45 connector
↓
Magnetics
↓
PHY side
↓
Controller
89. LAN Device Missing Flow
BIOS enabled?
↓
Controller power
↓
Reset
↓
Clock
↓
PCIe/host bus
↓
Controller
↓
Driver
90. Wi-Fi Missing Flow
Correct compatible card?
↓
3.3V
↓
Slot
↓
Enable/RF kill
↓
Reset
↓
Clock
↓
PCIe/CNVi
↓
BIOS
↓
Driver
91. Bluetooth Missing but Wi-Fi Works Flow
BT enabled?
↓
Driver
↓
USB data path from card
↓
Card connector
↓
Combo card internal BT section
↓
PCH/SoC USB controller
92. Weak Wi-Fi Flow
Known-good router/device comparison
↓
Antenna connectors
↓
Antenna wires
↓
Lid antennas
↓
Known-good Wi-Fi card
↓
RF section
93. LAN Speed Only 100 Mbps
If system/router/cable should support Gigabit:
Possible:
Bad Ethernet cable pair
RJ45 damaged pair
Magnetics
PHY path
Negotiation setting
Driver
94. LAN Link Drops when Cable Moves
Likely:
RJ45 contacts
Broken solder
Cable
Connector flex
Physical issue before controller IC.
95. LAN Controller Heating
Controller can warm normally.
Abnormal immediate heating + rail low resistance:
Controller/internal short possible.
Confirm rail and surrounding capacitors.
96. LAN Transformer Heating?
Ethernet magnetics normally should not be obvious high-heat source.
Abnormal heat indicates unusual fault and power should be removed for inspection.
97. Network Driver vs Hardware
If device appears correctly but warning icon:
Driver/resource problem.
If BIOS diagnostics detect network adapter:
Hardware is at least partially functional.
98. Windows Reinstall Before Board Repair?
Not always necessary.
Use quicker checks:
Device Manager
BIOS
Live OS
Known-good drivers
Network boot/diagnostic where available.
Avoid unnecessary customer-data risk.
99. MAC Address Shows 00:00:00...
Possible:
Firmware/configuration/EEPROM issue.
Not automatically LAN PHY hardware.
Board-specific data may need restoration from original backup.
100. PXE Boot
PXE:
Network boot over Ethernet.
If LAN hardware initializes correctly, BIOS may offer PXE/network boot.
Useful diagnostic clue.
101. Wake-on-LAN
LAN controller can stay partially powered in standby to detect network wake packets.
This means some LAN rails may be present even laptop off.
Exact settings/design vary.
102. Wi-Fi Power State
Wi-Fi card sleep/off states:
Power-save
Airplane mode
S3/S0ix
can alter rails/signals.
Measure in correct power state.
103. Modern Standby
New laptops may use S0ix/Modern Standby instead of classic S3.
Wireless card may remain in low-power connected state.
Power behavior differs from older platforms.
104. Wi-Fi 6 / 6E / 7
Newer Wi-Fi generations add:
Higher speed
new bands
advanced MIMO/channel features
But board repair basics same:
Power
Host interface
RF path
Antennas
Driver/firmware.
105. RF Section Kya Hai?
Wi-Fi card ke andar:
Transceiver
Power amplifier
Low-noise amplifier
Filters
RF switches
matching network
ho sakte hain.
Board-level laptop repair mein combo-card replacement often more practical than RF IC-level work.
106. Motherboard-Soldered Wi-Fi
Some laptops Wi-Fi module motherboard par soldered hota hai.
Then diagnosis:
Power
reset
host interface
RF/antenna
firmware
board-level components
required.
107. Antenna Lid Replacement
If display lid/hinge repair ke baad signal weak:
Antenna cable pinched/broken possible.
Always inspect routing.
108. Hinge Damage and Wi-Fi
Antenna wires hinges se pass hoti hain.
Repeated lid movement:
Cable damage.
Symptoms:
Signal changes with lid angle.
Random disconnect.
109. Webcam + Wi-Fi Antenna Area
Display lid mein:
Webcam
Mic
Wi-Fi antennas
close areas mein ho sakte hain.
But electrical circuits separate.
One cable repair se antenna disturb ho sakta hai.
110. Wi-Fi Card Antenna Connector ko Solder?
Tiny RF connector damaged ho to microsolder repair possible for skilled technician, but RF geometry matters.
Correct replacement connector/card use karna often more reliable.
111. Ethernet Port Transformer Measurement
Unpowered continuity/resistance comparison across magnetics may help detect open windings.
But exact pin pairs schematic/datasheet se identify karo.
Random RJ45 pins short mat karo.
112. Ethernet Signal Scope Testing
PHY differential pairs high-speed signals hain.
Advanced oscilloscope/probing required.
Basic shop diagnosis:
Known-good cable
link LEDs
magnetics continuity
device detection
controller rails
often enough hota hai.
113. LAN LED Circuit
RJ45 LEDs separate LED control pins se drive hoti hain.
One LED dead:
Ethernet may still work.
So no LED alone full LAN fault proof nahi unless link itself also absent.
114. Wi-Fi LED Indicator
Older laptops WLAN indicator LED use karte hain.
LED state can be controlled by EC/card.
LED off doesn't automatically mean card unpowered.
115. Bluetooth Audio Stutter
Possible:
RF interference
driver
antenna
Wi-Fi coexistence
card fault
power management
Not necessarily audio codec issue.
116. Wi-Fi/Bluetooth Coexistence
Combo cards both radios close frequencies use kar sakti hain.
Firmware coordinates them to reduce interference.
Bad driver/firmware may create performance issues.
117. 2.4 GHz Bluetooth Relation
Bluetooth operates around 2.4GHz band.
Heavy Wi-Fi 2.4GHz interference can affect performance.
This is not necessarily motherboard fault.
118. Network Schematic Search Terms
LAN:
LAN
ETH
ETHERNET
RJ45
PHY
GBE
LAN_RST
LAN_3V3
Wi-Fi:
WLAN
WIFI
WLAN_3V3
W_DISABLE
PERST
CLKREQ
CNVI
Bluetooth:
BT
BT_USB
USB_BT
119. BoardView LAN Strategy
Locate:
RJ45
Magnetics
LAN PHY/controller
25MHz crystal
Power ferrite beads
ESD protection
PCIe coupling components
120. BoardView Wi-Fi Strategy
Locate:
M.2 WLAN connector
3.3V power branch
Reset line resistor
CLKREQ#
PCIe/CNVi lines
Bluetooth USB lines
Antenna connectors are on card, not motherboard slot.
121. LAN Diagnostic Worksheet
Laptop Model: __________
Board Number: __________
LAN Controller: __________
Device Detected: Yes / No
Main VCC: __________
Core VCC: __________
Reset: __________
Clock: __________
Link LED: __________
Known-Good Cable: __________
RJ45 Condition: __________
Magnetics: __________
Final Fault: __________
122. Wi-Fi/Bluetooth Diagnostic Worksheet
Wi-Fi Card Model: __________
Interface: PCIe / CNVi / Other
3.3V: __________
WLAN Enable: __________
PERST#: __________
REFCLK: Present / Missing / Not Tested
Wi-Fi Detected: Yes / No
Bluetooth Detected: Yes / No
Antenna Main: __________
Antenna Aux: __________
Signal Strength: __________
Known-Good Card Result: __________
Final Fault: __________
123. Case Study 1 — LAN Device Missing
Controller 3.3V missing.
Source 3.3V present.
Ferrite bead input = 3.3V.
Output = 0V.
Likely open power path.
No reason to replace RJ45 first.
124. Case Study 2 — LAN Device Present, Cable Not Detected
Known-good cable/router.
Device Manager okay.
No link LED.
Focus:
RJ45
Magnetics
PHY analog side.
125. Case Study 3 — LAN Only 100Mbps
Known-good Gigabit router.
Known-good Cat5e/6 cable.
Same laptop stays 100Mbps.
Inspect:
All Ethernet pairs
RJ45
Magnetics
PHY.
126. Case Study 4 — Wi-Fi Missing, Bluetooth Works
Combo card Bluetooth detected.
Wi-Fi absent.
Main card power likely present.
Focus:
Wi-Fi PCIe/CNVi side
PERST#
REFCLK
WLAN enable
card Wi-Fi section.
127. Case Study 5 — Wi-Fi Works, Bluetooth Missing
Focus:
Bluetooth USB lines
Driver
Card BT section
USB controller.
128. Case Study 6 — Wi-Fi Range Extremely Weak
Wi-Fi card detected.
Connects only beside router.
Inspect:
MAIN/AUX antenna connectors.
Antenna cable routing.
Lid antenna.
Known-good card.
129. Case Study 7 — One Antenna Cable Disconnected
Laptop still connects.
Speed/range lower.
After correct reconnection:
Performance normal.
Motherboard repair not required.
130. Case Study 8 — Wi-Fi Card Very Hot, 3.3V Rail Low
Remove card.
3.3V rail returns normal.
Known-good compatible card works.
Original card internally faulty.
131. Case Study 9 — Wi-Fi Missing after Screen Replacement
Before repair normal.
After display/hinge repair weak/no signal.
Check antenna cables and lid routing first.
132. Case Study 10 — Airplane Mode Stuck
Wi-Fi hardware appears in Device Manager.
Radio disabled.
Check:
OS setting
hotkey software
EC/RF-kill signal
BIOS settings
before replacing card.
133. Case Study 11 — Wi-Fi Missing with New Card
Old card type CNVi.
Replacement normal PCIe M.2 card.
Physically fits but no detection.
Compatibility issue, not necessarily motherboard fault.
134. Case Study 12 — Bluetooth Headset Stutters but Wi-Fi Strong
Check:
Driver
2.4GHz interference
Bluetooth antenna/card
power-management settings
before laptop audio codec.
135. Network Repair Golden Rules
1. LAN, Wi-Fi aur Bluetooth ko separate circuits samjho.
2. Ethernet device detect hona aur cable link hona different stages hain.
3. RJ45 se pehle PHY/magnetics architecture samjho.
4. Wi-Fi card ko power + enable + host interface + antenna chahiye.
5. Wi-Fi aur Bluetooth same card par hoke bhi different host interfaces use kar sakte hain.
6. Weak Wi-Fi ka common cause antenna hai, motherboard nahi.
7. M.2 physical fit compatibility guarantee nahi.
8. Device Manager software vs hardware diagnosis mein bohat useful hai.
9. High-speed RF/Ethernet lines par random voltage/jumpers mat lagao.
10. Known-good card/cable/router comparison diagnosis ko bohat fast karta hai.
136. Part 14 Quick Revision
LAN
Wired local network.
MAC
Network data-link control.
PHY
Ethernet physical-layer transceiver.
RJ45
Ethernet connector.
Magnetics
Ethernet isolation transformer/filter system.
Wi-Fi
Wireless network radio.
M.2 WLAN
Wi-Fi card interface/form factor.
WLAN_EN
Wireless enable control.
W_DISABLE#
Wireless disable signal.
MAIN / AUX
Wi-Fi antenna connections.
Bluetooth
Short-range wireless protocol.
Combo Card
Wi-Fi + Bluetooth same module.
CNVi
Intel integrated wireless architecture family.
MIMO
Multiple antennas/data streams.
137. Part 14 ka Sabse Important Lesson
Network fault mein pehle ye decide karo:
LAN problem hai, Wi-Fi problem hai ya Bluetooth problem?
LAN:
Controller detected?
↓
Link hai?
↓
Magnetics / RJ45 / Cable
Wi-Fi:
Card detected?
↓
3.3V / Enable / Reset / Host interface
↓
Antenna / RF
Bluetooth:
Wi-Fi same card par work kar raha?
↓
Bluetooth USB path / Driver / Card
Yani network repair mein bhi same formula:
Power → Control → Communication → Physical Interface
Jahan first missing condition mile, wahi fault area hai.
Part 14 Complete
Next — Part 15: Keyboard, Touchpad, Power Button, Lid Sensor aur Input Devices Complete Mastery
Part 15 mein hum detail se cover karenge:
Keyboard matrix.
Rows/columns.
EC/KBC keyboard scanning.
Keyboard connector.
Keyboard backlight.
Touchpad power.
I2C touchpad.
PS/2 legacy touchpad.
Touchpad reset/interrupt.
Power button board.
Fingerprint sensor.
Hall/lid sensor.
Webcam basics.
Laptop keyboard completely dead.
Some keys dead.
Touchpad missing.
Touchpad works in BIOS but not Windows.
Power button dead.
Laptop automatically sleeps because lid sensor.
Aur complete EC/KBC se input devices tak diagnostic flow.
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