Practical Skills, Circuit Assembly and Safety
What this domain covers
Practical Skills, Circuit Assembly and Safety tests how you build, inspect and test circuits without damaging components or yourself: breadboarding, soldering, PCB work, measurement discipline and electrical safety.
Core rules
- Breadboard rows are connected in groups of five across the centre channel; the outer rails are the supply buses. Keep power and ground rails separate.
- Good soldering: clean and tin the iron, heat the joint and feed solder into the joint (not onto the iron), aim for a shiny concave fillet, and avoid cold or bridged joints.
- Component handling: observe polarity for electrolytic capacitors, diodes and ICs; discharge large capacitors before working; use an anti-static wrist strap for CMOS devices.
- Safety: work with one hand where possible, use an isolation transformer for mains-powered bench work, ensure proper earthing, fit a fuse of correct rating, and never touch a circuit while it is live.
- Testing: use the diode/continuity range with power off; compare measured node voltages with expected values to localise a fault.
Worked example
A bridge rectifier output is dead. With power off, the DMM diode test reads 0.6 V from each AC input to the + terminal in one direction and OL in the other - normal. One diode reads OL in both directions, indicating an open diode; replacing it restores the output.
Traps that cost marks
Soldering with a dirty tip or moving the joint before it freezes; fitting an electrolytic capacitor backwards; probing a live board with the meter set to resistance; and ignoring the voltage rating of a replacement capacitor.