Odisha CHSE +2 Vocational Mobile Technology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

SoC

System on Chip: a single IC that integrates CPU, GPU, modem, image processor and memory controller. It is the main processing block of a smartphone and sits on the main power rails from the PMIC.

PMIC

Power Management IC: converts battery voltage into the multiple regulated rails needed by the SoC, display, camera and radios. A missing output rail points to the PMIC or its load.

Li-ion nominal voltage

A lithium-ion phone battery is rated 3.7 V nominal, charges to 4.2 V and cuts off near 3.0–3.3 V. Readings far outside this range indicate a discharged, aged or faulty cell.

eMMC and UFS

Embedded flash storage standards used in phones. eMMC uses a parallel interface, UFS is faster and serial. Both hold firmware and user data and are common causes of boot loops.

LDI water indicator

Liquid Damage Indicator: a label that changes from white to red or pink on water contact. It gives evidence of liquid exposure, which usually voids warranty and explains corrosion faults.

Audio codec IC

Chip that converts digital audio to analog for speaker and earpiece and digitizes microphone input. A single dead output usually means the transducer or its flex, not the codec.

LTE

Long Term Evolution, the 4G cellular standard. It is all-IP, uses OFDMA downlink and SC-FDMA uplink, and needs a USIM plus support for the operator's frequency band.

5G NR band n78

The 3300–3600 MHz band widely used for 5G in India. A phone must support n78 to register on those networks; band support is a specification, not a repair issue.

RSRP

Reference Signal Received Power: an LTE signal-strength measure in dBm. About −80 dBm is good and below −110 dBm is very weak, causing dropped calls or loss of service.

SINR

Signal to Interference plus Noise Ratio: quality measure in dB. High RSRP with low SINR means interference rather than distance, so moving closer to the tower will not help.

IMEI

International Mobile Equipment Identity: a 15-digit device identifier. A blacklisted, null or duplicated IMEI causes network rejection even when the SIM and signal are good.

SIM reader fault

When a known-good SIM shows no service, suspect bent reader pins, the SIM power rail or a blocked IMEI. Test with a second SIM and measure the SIM supply voltage.

ART

Android Runtime: executes Android apps, replacing the older Dalvik VM. It compiles app bytecode ahead of time or just in time, and its crashes appear as FATAL EXCEPTION in logs.

Fastboot mode

A bootloader-level USB mode used to flash firmware partitions such as boot and system. It works even when Android does not start, so it helps separate software from hardware boot faults.

Recovery mode

A separate boot partition used to apply OTA updates and wipe cache or data. Factory reset from recovery erases user data but does not rewrite the main firmware image.

ADB

Android Debug Bridge: a command-line tool over USB or Wi-Fi. Commands include adb devices, adb shell, adb logcat and adb reboot, used for diagnosis and log collection.

Bootloader lock

A security state that blocks flashing unsigned firmware. Unlocking it usually wipes all data and may void warranty, so customer consent must be recorded first.

Boot loop causes

Repeated restart before the home screen. Software causes include corrupt updates and wrong firmware; hardware causes include failing eMMC and sagging power rails under load.

ESD wrist strap

A strap with a 1 MΩ resistor that safely drains static charge from the technician to ground. It protects CMOS ICs from damage by discharges too small for a person to feel.

Multimeter diode mode

A mode that shows voltage drop across a junction, useful for finding shorted rails and testing tracks. Power must be removed from the board before resistance or diode tests.

Current-limited supply test

Powering a board from a bench supply with a low current limit. A shorted rail draws current immediately at low voltage, while a healthy board draws almost nothing.

Hot-air rework settings

Typical settings are 350–400 °C with moderate airflow after preheating the board to 100–150 °C. Preheat reduces thermal shock and warping of thin phone boards.

Swollen battery handling

A swollen or venting lithium-ion cell must never be charged. Isolate it in a fire-resistant container, avoid puncture, and dispose through authorized e-waste channels.

Dead short isolation

If a rail reads near 0 Ω to ground, inject a current-limited voltage and find the warming component with a thermal camera or alcohol evaporation, then replace that part.

No-charging test order

Check charger and cable, then port pins, charging IC input, battery FET and battery. Bent VBUS or ground pins in the port are the most frequent cause of no charging.

No display but phone boots

If the phone vibrates, sounds or is detected by a PC, the fault lies in the display flex, connector, backlight rail or display IC rather than the main board boot path.

Cold solder joint

A dull, cracked or ball-shaped joint with poor wetting, often intermittent. Flexing the board while monitoring a rail or signal exposes the fault, and rework with flux fixes it.

Solder wick

Desoldering braid that absorbs excess solder from pads and joints. Add fresh solder and flux first so old oxidized solder flows into the braid, then clean the area.

BGA reballing

Replacing the solder balls on a ball-grid-array package. Pads are cleaned, a stencil is aligned, paste or preformed balls are applied, and the part is reflowed with hot air.

Service intake record

A written intake form capturing customer details, IMEI, reported fault, accessories and cosmetic condition with a signature. It protects both shop and customer in later disputes.

Repair handover checklist

A final test of call, speaker, earpiece, microphone, camera, touch, charging, Wi-Fi, Bluetooth, sensors and network registration before the device is returned to the customer.

Break-even point

Fixed cost divided by the difference between selling price and variable cost per unit. It gives the number of repairs or sales needed before the business makes a profit.