Mobile Repair Tools, Instruments and Safety Practices
This domain covers the bench equipment and safety discipline used in mobile repair. The exam tests correct instrument selection, safe measurement and recognition of hazards such as lithium batteries, hot tools and electrostatic discharge (ESD).
Measuring instruments
A digital multimeter measures voltage, current, resistance and continuity. Voltage is measured in parallel with the circuit powered; current in series with the supply; resistance and continuity only on an unpowered, isolated board. A DC power supply with current limit replaces the battery for boot-current analysis. An oscilloscope displays waveforms and is useful for clocks, data lines and ripple, but its probe ground must be connected correctly. A hot-air rework station and soldering iron have separate temperature settings; a microscope aids fine-pitch inspection.
Safety and ESD
Use a grounded ESD wrist strap and mat when handling boards. Work in a ventilated area with fume extraction; wear safety glasses when clipping or cleaning. Lithium-ion batteries can swell, vent or ignite: do not puncture, bend or heat them, and store swollen packs in a fire-resistant container. Disconnect power before soldering. Keep liquids away from the bench.
Worked example
To check a phone’s standby current, set a current-limited DC supply to the battery’s nominal voltage, for example 3.8–4.2 V, connect polarity correctly, and observe the draw before pressing power. A high current may indicate a shorted rail; zero current may indicate an open input path. Never start at a high current limit.
Traps
Resistance tests on a live board give meaningless readings and can damage the meter. A continuity beep does not prove a component is good under load. Do not use hot air near a battery or use a metal tool to pry a swollen pack.