EivoTech Laptop & Mobile Repair Master Course
Final Mobile Repair Technician Exam — Answer Key Part 4
Questions 121–160 Complete Answers
Section I — Battery Drain + Heating + Shutdown Continued
Question 121
Airplane mode battery drain ko dramatically improve karta hai. Kis subsystem ki direction strong hai?
Answer:
Strong direction:
CELLULAR / RF / NETWORK ACTIVITY
Airplane mode usually cellular radio activity ko disable karta hai.
Agar drain dramatically improve ho:
Check:
Weak network signal
Constant network searching
Antenna path
Cellular RF subsystem
Carrier/network behavior
Important:
Iska matlab automatically PA faulty nahi.
Pehle network/antenna conditions verify karo.
Golden Rule:
AIRPLANE MODE SOLVES DRAIN → WIRELESS/RF DIRECTION STRONG
Question 122
Phone idle mein warm hai. Airplane mode se koi difference nahi. Software background usage bhi normal. Next direction?
Answer:
Ab hardware leakage/active rail direction stronger hoti hai.
Diagnostic thinking:
SLEEP STATE → ACTIVE RAIL → ABNORMAL LOAD → ROOT CAUSE
Check:
Phone actually sleep mein ja raha hai?
Any secondary rail unnecessarily active?
Liquid/corrosion history?
External module leakage?
Abnormal rail resistance?
Thermal location clue use ho sakta hai, lekin hottest component ko direct faulty mat bolo.
Question 123
Short aur leakage mein difference explain karo.
Answer:
Hard Short
Very low-resistance unwanted path.
Possible:
Rail almost directly ground/load ki taraf pulled.
Symptoms:
Very low resistance
High abnormal input load
Rail fail/protection
Leakage
Partial unwanted current path.
Resistance hard short jitni low zaroori nahi.
Symptoms:
Battery drain
Idle heating
Sleep current high
Intermittent instability
Simple Formula:
SHORT = STRONG UNWANTED CURRENT PATH
LEAKAGE = SMALLER/PARTIAL UNWANTED CURRENT PATH
Question 124
PMIC hottest component hai. Why is that not enough to replace PMIC?
Answer:
PMIC multiple downstream rails ko power deta hai.
Agar downstream load short/leak ho:
PMIC excessive current deliver karte hue warm ho sakta hai.
Possible root causes:
Shorted capacitor
Camera module
Audio amp
RF load
Corrosion
Other peripheral
Correct process:
HOT PMIC → CHECK OUTPUT RAILS → FIND ABNORMAL LOAD
Rule:
HEAT LOCATION = CLUE, NOT FINAL DIAGNOSIS
Question 125
Phone only camera use par shutdown karta hai. Known-good battery se same. First subsystem-specific checks?
Answer:
Focus:
CAMERA SUBSYSTEM
Check:
Which camera triggers shutdown?
Known-good camera module
Camera power rails
Camera PMIC/output
Rail behavior when camera activates
First Falling Point
If one camera replacement solves:
Original camera module strong root cause.
Question 126
Phone only cellular call par restart karta hai. Known-good battery fixes. Root cause?
Answer:
WEAK / DEGRADED BATTERY UNDER RF LOAD
Cellular transmit can create high dynamic power demand.
Old battery idle mein normal lag sakti hai but load par voltage sag kar sakti hai.
Confirmation:
Known-good battery → call stable.
Strong battery fault confirmation.
Question 127
Known-good battery same fault. RF supply collapses first. Root direction?
Answer:
Strong direction:
RF SUPPLY / RF LOAD / PA POWER PATH
Because battery ruled out aur first falling point RF rail hai.
Next conceptual checks:
RF regulator/input
Enable/control
Output rail loading
PA/FEM-related load
RF power path
Golden Rule:
FIRST FALLING RAIL ROOT-CAUSE AREA KO NARROW KARTI HAI
Section J — Schematic + BoardView + Oscilloscope
Question 128
Schematic aur BoardView ka difference explain karo.
Answer:
Schematic
Electrical relationship dikhata hai.
Batata hai:
Component kis net par hai
Signal kahan se aata hai
Kahan jata hai
Circuit blocks ka relation
BoardView
Motherboard par component ki:
PHYSICAL LOCATION
dikhata hai.
Simple:
SCHEMATIC = ELECTRICAL MAP
BOARDVIEW = PHYSICAL MAP
Dono saath use karna best hai.
Question 129
Reference designators ka meaning likho.
Answer:
Common designators:
R = Resistor
C = Capacitor
L = Inductor / Coil / sometimes Ferrite
U = Integrated Circuit / IC
Q = Transistor / MOSFET
D = Diode
F = Fuse
J = Connector / Jack
Manufacturer naming slightly differ kar sakti hai.
Question 130
Last Good → First Missing method example ke saath explain karo.
Answer:
Is method mein signal/power flow ko sequence mein trace karte hain.
Example:
Regulator circuit:
VIN = present.
EN = present.
OUT = missing.
Then:
LAST GOOD = EN / INPUT STAGE
FIRST MISSING = OUTPUT
Ab regulator/output-load area diagnose karenge.
Purpose:
Random IC guessing ki jagah fault ko exact stage tak narrow karna.
Question 131
Regulator output missing hai. Schematic se diagnostic path kaise trace karoge?
Answer:
Master formula:
VIN → EN → OUT → PGOOD → LOAD
Steps:
Regulator identify.
VIN source trace.
Enable source trace.
Output net identify.
Output consumers inspect.
Output rail resistance compare.
PGOOD/feedback where applicable check.
Example:
VIN missing → upstream.
EN missing → control.
VIN + EN good, output missing → output regulator/load direction.
Question 132
Oscilloscope multimeter se kab better hota hai? Kam az kam 5 examples.
Answer:
Oscilloscope useful jab signal time ke saath rapidly change karta ho.
Examples:
Clock signal
Reset pulse
Startup rail pulse
Enable timing
Boot-loop rail collapse
I2C activity
PWM
Voltage ripple
First Falling Point
Short transient events
Simple:
MULTIMETER = STATIC/AVERAGE
SCOPE = TIME-BASED BEHAVIOR
Question 133
Multimeter rail par low unstable voltage show karta hai. Scope par rail correct level tak briefly rise karke collapse karti hai. Is se kya clue milta hai?
Answer:
Multimeter average reading misleading thi.
Scope proves:
REGULATOR ACTUALLY START KAR RAHA HAI
Rail initially correct level achieve karti hai, then shutdown/collapse hoti hai.
Next investigate:
Load
Protection
Enable behavior
First Falling Point
Question 134
Enable first drops, phir output rail girti hai. Upstream ya downstream direction?
Answer:
Strong direction:
UPSTREAM CONTROL / SHUTDOWN COMMAND
Because regulator ko pehle disable kiya gaya.
Sequence:
EN ↓
Then VOUT ↓
Regulator may simply be following command.
Question 135
Output rail collapses while enable remains active. Direction?
Answer:
Strong direction:
REGULATOR / OUTPUT LOAD SIDE
Possible:
Excessive load
Short/leak
Regulator failure
Protection/current limiting
Because control still requests rail ON.
Question 136
I2C activity scope par nazar aa rahi hai. Kya iska matlab data 100% correct hai?
Answer:
Nahi.
Activity proves bus par transitions ho rahi hain.
But it doesn't automatically prove:
Correct address
Correct data
Proper acknowledgements
Timing completely valid
Device response correct
For deeper protocol interpretation:
Logic/protocol analysis may be required.
Rule:
ACTIVITY ≠ VALID COMMUNICATION
Question 137
Normal oscilloscope se actual Wi-Fi/cellular GHz RF fully diagnose kyun nahi hoti?
Answer:
Wi-Fi/cellular RF signals very high-frequency radio domain mein operate karte hain.
Normal motherboard scope:
Required RF bandwidth na rakhe
RF power/frequency accurately analyze na kare
Impedance/matching measurement ke liye designed na ho
Advanced RF diagnosis may require:
Spectrum analyzer
Network analyzer
RF test equipment
Lesson:
Normal scope ko GHz RF analyzer mat samjho.
Section K — BGA + Sandwich + Foldable / Tablet
Question 138
BGA ka full form kya hai?
Answer:
BALL GRID ARRAY
IC ke solder connections package ke neeche grid form mein hoti hain.
Question 139
BGA ko last-stage suspect kyun rakhna chahiye?
Answer:
Because BGA/major IC work:
High risk
Difficult
Expensive
Board/data damage risk
Unnecessary ho sakta hai if easier fault exists
Pehle prove karo:
POWER → CLOCK → RESET → COMMUNICATION → EXTERNAL PATH → PCB PATH
Then BGA.
Question 140
Random reflow ko diagnosis kyun nahi keh sakte?
Answer:
Heat multiple variables change karti hai:
Solder expansion
PCB expansion
IC temperature
Leakage
Nearby components
Temporary behavior change root cause prove nahi karta.
Rule:
HEAT RESPONSE ≠ BGA CONFIRMATION
Question 141
Heat se behavior temporarily change ho jaye to kya BGA confirm ho gaya?
Answer:
Nahi.
Possible causes:
BGA joint
Internal IC issue
PCB micro-crack
Nearby component
Temperature-dependent leakage
More evidence needed.
Question 142
UFS BGA ko suspect karne se pehle kaun se prerequisites prove karoge?
Answer:
Check:
UFS power rails
Reset
Required clock
SoC startup
Power stability
Official flash/restore behavior
External cable/PC/software causes
PCB path where measurable
Then storage IC/BGA becomes valid late-stage suspect.
Question 143
No Service phone mein baseband info present aur signal weak hai. Baseband BGA ya antenna/RF first?
Answer:
ANTENNA / RF PATH FIRST
Baseband information present means digital baseband subsystem significantly alive.
Weak signal strongly points toward:
Antenna contact
Coax
Filter
LNA/FEM
RF path
Question 144
Wi-Fi weak hai but toggle and Bluetooth digital functions normal. Wi-Fi BGA ya RF first?
Answer:
RF / ANTENNA FIRST
Feature initializes normally.
Weak range is typically RF path problem before combo IC BGA.
Question 145
Sandwich/interposer fault ko suspect karne ke strong clues kya hain?
Answer:
Strong clues:
Hard-drop history
Multiple related intermittent faults
External modules ruled out
Source-side signals present
Destination-side signals missing
Multiple affected nets cross same interposer region
Board-to-board path instability
Rule:
INTERPOSER FAULT = EVIDENCE-BASED LATE-STAGE CONCLUSION
Question 146
Hard drop ke baad No Service aaya. Board separate karne se pehle kya-kya check karoge?
Answer:
First check:
Known-good SIM
SIM detection
Baseband information
Antenna contacts
Coax cables
RF connectors
RF front-end
Baseband power/control
Visible board damage
Board separation first diagnostic step nahi.
Question 147
Foldable phone inner display dead hai but outer display works. Diagnostic block?
Answer:
Strongly localized to:
INNER DISPLAY SUBSYSTEM
Check:
Inner panel
Inner display connector
Hinge flex/interconnect
Inner display power
Reset/data path
Outer display working suggests complete SoC/display engine failure less likely.
Question 148
Foldable phone sirf half-fold position par restart karta hai. Strong suspect area?
Answer:
HINGE FLEX / INTERCONNECT / POSITION-DEPENDENT MECHANICAL PATH
Possible:
Battery interconnect
Display flex
Main-to-secondary board path
Hinge wiring
Do not repeatedly stress/flex device unnecessarily.
Question 149
Dual-battery device mein one battery not detected. Kin lines/systems ko check karoge?
Answer:
Check:
Battery module connector
Battery positive/ground path
Temperature sensing
ID/data lines
Battery-detection communication
Power-management system
Known-good compatible pack comparison can help.
Question 150
Dual battery packs ko manually parallel/direct-charge kyun nahi karna chahiye?
Answer:
Dual-battery architecture can use sophisticated protected power-management.
Manual cell connection/direct charging can bypass:
BMS/protection
Temperature monitoring
Charge balancing/control
Device-specific limits
Result dangerous battery damage/overheating ho sakta hai.
Rule:
COMPLETE PROTECTED BATTERY MODULES KO USE KARO — CELLS KO MANUALLY MODIFY NAHI
Question 151
Tablet finger touch works but stylus dead. Kis subsystem ko separately diagnose karna hai?
Answer:
STYLUS / ACTIVE DIGITIZER SUBSYSTEM
Check:
Known-good compatible stylus
Stylus power/accessory state
Digitizer controller
Digitizer power
Communication
Finger capacitive touch working stylus digitizer ko automatically prove nahi karta.
Question 152
Tablet charges normally but external USB-C display output dead. Kya charging path automatically high-speed path ko prove karta hai?
Answer:
Nahi.
USB-C port mein separate functions ho sakte hain:
VBUS charging
CC
USB data
High-speed lanes
DisplayPort Alt Mode
Mux
Charging working only power-related path significantly prove karta hai.
External display failure mein check:
Device feature support
Cable/adapter
USB mux/control
High-speed path
Final Master Oral Questions
Question 153
Aap ke paas ek completely unknown dead phone aaye. First 10 diagnostic steps verbal sequence mein batao.
Answer:
Professional sequence:
1.
Customer complaint verify karo.
2.
History lo:
Drop, liquid, previous repair, charging event.
3.
Physical inspection.
4.
Known-good compatible battery/input test.
5.
Confirm whether phone truly no-power hai ya no-display.
6.
Main battery rail check.
7.
Main-rail resistance/short check with power removed.
8.
PMIC input check.
9.
Always-on/standby rails check.
10.
Power-key → startup rails → CPU/RAM/storage boot sequence trace karo.
Then:
LAST GOOD → FIRST MISSING
Question 154
Aapko ek unknown rail par continuity beep milti hai. Is reading ko interpret karne ka complete process batao.
Answer:
Direct “short” mat bolo.
Process:
Exact net identify.
Board power remove.
Resistance-to-ground measure.
Determine rail type.
Ask whether naturally low-resistance rail hai.
Known-good same-model compare.
BoardView par consumers map.
Other same-net capacitors compare.
Boot/function behavior consider.
Only evidence ke baad short confirm.
Golden Rule:
BEEP → INVESTIGATE
not:
BEEP → SHORT CONFIRMED
Question 155
Customer kehta hai: “Phone ka motherboard short hai.” Aap technician ke taur par is statement ko kaise verify karoge?
Answer:
Customer complaint ko diagnosis nahi samjho.
First determine actual symptom:
No power?
No charge?
Heating?
Battery drain?
Then:
Known-good external tests
Power removed
Main rail resistance
Compare known-good
Exact affected rail identify
Net map
Branch isolate
Root component confirm
Formula:
CUSTOMER STATEMENT → VERIFIED SYMPTOM → ELECTRICAL EVIDENCE → DIAGNOSIS
Question 156
Ek phone repair ke baad ON ho gaya. Kya repair complete hai? Full QC ka reason explain karo.
Answer:
Nahi.
Phone ON hona only one condition prove karta hai.
Repair ke baad check:
Charging
Display/touch
Audio
Cameras
Network
Wi-Fi/Bluetooth
Sensors
Buttons
Battery/thermal
Original complaint
Especially liquid/board repair mein multiple faults ho sakte hain.
Rule:
REPAIR COMPLETE = ROOT CAUSE FIXED + FULL QC PASSED
Question 157
“Current draw 0.xxA = UFS fault.” Is statement mein technical problem kya hai?
Answer:
Current value:
UNIVERSAL FAULT CODE NAHI
Same current reading different phones/states mein different meaning rakh sakti hai.
Current depends on:
Model
SoC
Boot stage
Display
Firmware
Peripherals
Correct method:
CURRENT PATTERN → BOOT STAGE → RAIL MEASUREMENTS → FIRST MISSING/FALLING
Question 158
“IC garam hai = IC faulty.” Is statement mein problem kya hai?
Answer:
IC downstream load ko power de raha ho sakta hai.
Heat could result from:
Downstream short
Heavy normal load
Cycling
Leakage
IC fault
Therefore:
HOT IC = CLUE
Then:
Input/output rails
Load resistance
Isolation
Function
check karo.
Question 159
“Phone drop hua = CPU reball.” Is approach mein kya galat hai?
Answer:
Drop can damage many easier things:
Display
Battery
Connector
Flex
Antenna
Coax
PCB
Solder joints
CPU is only one possible late-stage cause.
Correct order:
PHYSICAL INSPECTION → EXTERNAL MODULE → POWER → SIGNALS → PCB PATH → BGA LAST
Random BGA work unnecessary risk create karta hai.
Question 160
Professional repair technician aur parts-changing technician mein kya difference hai?
Answer:
Parts-Changing Technician
Often:
Symptom dekha.
↓
Part guess kiya.
↓
Replace kiya.
↓
Try kiya.
Professional Diagnostic Technician
Uses:
SYMPTOM → HISTORY → SYSTEM → BLOCK → MEASUREMENT → LAST GOOD → FIRST MISSING → CONFIRMATION → ROOT CAUSE
Professional technician:
Measurement record karta hai
Schematic use karta hai
Known-good comparison karta hai
Customer data protect karta hai
Major IC ko last suspect rakhta hai
Full QC karta hai
Final Difference:
PARTS CHANGER COMPONENT GUESS KARTA HAI
DIAGNOSTIC TECHNICIAN FAULTY STAGE PROVE KARTA HAI
Answer Key Part 4 — Questions 121–160 Complete ✅
Final Theory Answer Key Status
Questions 1–40
✅ Answer Key Part 1
Questions 41–80
✅ Answer Key Part 2
Questions 81–120
✅ Answer Key Part 3
Questions 121–160
✅ Answer Key Part 4
Questions 1–160 Complete ✅
Ab Final Remaining Section
Theory exam complete ho gaya.
Ab sirf:
25 FINAL ADVANCED PRACTICAL CASES — COMPLETE ANSWER KEY
remaining hai.
Usmein har case ko simple answer se nahi, balki proper format mein solve karenge:
SYMPTOM
↓
IMPORTANT CLUE
↓
LAST GOOD
↓
FIRST MISSING / FIRST FALLING
↓
DIAGNOSTIC DIRECTION
↓
CONFIRMATION
↓
ROOT CAUSE
Ye final practical answer key complete hone ke baad:
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