Fault Diagnosis, Servicing, Safety and Environmental Practices
What this domain tests
Fault Diagnosis, Servicing, Safety and Environmental Practices tests systematic troubleshooting, test procedures, safe isolation, ESD, CRT discharge, soldering hazards, and e-waste handling.
Core rules
- Start with a symptom interview and visual inspection: fuse, burnt components, bulged capacitors, loose connectors, corrosion.
- Use split-half signal tracing: confirm power rails, then inject or trace the signal from input to output or output to input.
- Measure voltage, resistance, and waveform, and substitute known-good modules only after evidence.
- Safety: unplug before resistance tests; discharge the CRT anode through a resistor to chassis; use an isolation transformer for live-chassis sets; avoid working alone on high voltage.
- ESD: wrist strap, grounded mat, avoid touching CMOS gates.
- Environmental: leaded solder and e-waste such as CRT glass, batteries, and PCBs go to authorized recyclers; do not burn cables.
Worked example
A dead colour TV shows no standby LED. Check the mains plug, fuse, and standby supply. If the fuse is blown, do not simply replace it: check the bridge rectifier, chopper transistor, and input filter for shorts. A shorted chopper will blow the new fuse. After repairing the primary, use a series lamp limiter for first power-up to limit fault current.
Traps
Replacing fuses without finding the short causes repeat failure. Assuming a CRT is safe after unplugging is dangerous. Using a multimeter on a live chassis risks shock. Mixing leaded and lead-free solder produces unreliable joints. Discarding CRTs as ordinary rubbish harms the environment.