Maintenance activities are essential in ensuring the reliability and longevity of electrical and electronic equipment used in Kenya’s industries, institutions, and service sectors. For electronics engineering professionals, performing effective maintenance not only minimizes downtime but also safeguards operational safety and optimizes performance. This chapter focuses on practical approaches to repairing and replacing faulty components, proper disposal of waste materials generated during maintenance, and adherence to environmental health and safety (EHS) regulations that govern these activities within Kenyan workplaces.

3.1 Repair/Replacement of faulty components

Repairing equipment means finding the failed part, removing it, fitting a sound part of the correct value, and proving that the equipment works again. A replacement made carelessly can introduce a new fault, damage the board or leave the equipment unsafe, so every replacement follows the same order:

1. Isolate the equipment from the supply and discharge any stored energy in capacitors.
2. Identify the faulty component from the symptoms, the circuit diagram and the test results.
3. Remove the faulty component without damaging the board, the leads or the neighbouring parts.
4. Check that the replacement matches the original in type, value, rating and package, and that it has the correct polarity or orientation.
5. Fit the replacement, and make the joint or connection properly.
6. Clean the area, reassemble the equipment, and test it before returning it to the owner.

Diagnosis and testing are treated in their own chapters of this unit. This topic deals with the maintenance activities that go into a repair and with the safe disposal of what a repair leaves behind.

3.1.1 Maintenance activities

Maintenance activities are the practical tasks carried out on equipment during a repair or a routine service: cleaning it, tightening what has come loose, soldering and desoldering joints, and putting the equipment back together. Done in this order, they remove the causes of many faults, such as dust, loose connections and dry solder joints, and they make the repair last. A technician servicing a television, an electric kettle or a mobile phone uses all four in nearly every job.

3.1.1.1 Cleaning

Dust, grease, flux residue and corrosion cause faults. Dust blankets a heat sink and a fan so that components overheat, and moisture and dust together form a conductive film that leaks current between tracks. Contacts and connectors that are oxidised give a poor connection that shows as crackling, flickering or intermittent operation.

Cleaning materials and tools:

• Soft brush: loosens dust from boards and from fan blades.
• Blower or low-pressure compressed air: removes loose dust from heat sinks and vents. A vacuum cleaner for electronics is anti-static, and an ordinary one can build up a static charge.
• Isopropyl alcohol (90 per cent or stronger) and lint-free swabs: remove flux and grime from boards and contacts, and evaporate quickly without leaving a residue.
• Contact cleaner: applied to switch contacts, sockets and potentiometers.

Cleaning is done with the equipment unplugged. The board is allowed to dry fully before power is applied. Water, household detergents and abrasive pads are not used on boards or contacts, because they leave a residue or scratch the tracks. Solvents are flammable, and the work is done in a ventilated area, away from soldering irons and flames.

3.1.1.2 Tightening

Heat, vibration and age loosen screws and terminals. A loose power terminal has a high contact resistance, so it heats up under load, discolours, arcs, and in the end damages the terminal block and the wire. A loose mounting screw lets a heavy component, such as a transformer or a power transistor on a heat sink, vibrate and crack solder joints.

Tightening is done with the correct tool and the correct force:

• The screwdriver or spanner must fit the screw or nut exactly, so that the head is not rounded off.
• Terminals are tightened until the conductor cannot be pulled out by hand, and no further. Where a torque value is given by the maker, a torque screwdriver is used.
• Screws that go into plastic or into a board are tightened gently, because the thread can strip and the plastic can crack.
• On a cover or a heat sink, screws are tightened in a cross pattern, so that the pressure is even.
• Where vibration is expected, a spring or toothed washer, or a drop of thread-locking compound, holds the screw.

The method of tightening screws on a finished repair is treated further in the chapter on assembling repaired equipment.

3.1.1.3 Soldering

Soldering joins a component lead to a copper pad on a board with a molten metal alloy (solder). A good joint is a mechanical and an electrical connection in one. A poor joint (a dry or cold joint) looks dull, grainy or lumpy and causes intermittent faults.

Tools and materials:

To replace a through-hole component:

1. Unplug the equipment and discharge capacitors.
2. Heat the joint of the faulty component and remove the solder with the pump or wick until the lead moves freely.
3. Remove the component and clean the pad and the hole.
4. Bend the leads of the new component to fit, and insert it in the correct orientation, following the polarity mark for diodes, electrolytic capacitors and transistors.
5. Touch the iron to the pad and the lead together for two to three seconds, and then feed in solder on the opposite side so that it flows around the lead.
6. Remove the solder and then the iron, and let the joint cool without moving it.
7. Trim the lead, and inspect the joint: it should be shiny, smooth and shaped like a small cone.

The tip temperature is commonly set between 320 °C and 350 °C for leaded solder and a little higher for lead-free solder, and the solder maker's data sheet is followed. Sensitive components, such as integrated circuits, are soldered into sockets where possible, and are handled by their edges at a bench with an anti-static wrist strap, so that static does not damage them. Soldering gives off fumes from the flux, so a fume extractor or good ventilation is used, the iron is returned to its stand, never left on the bench, and hands are washed after handling leaded solder.

3.1.1.4 Assembling

Assembling is putting the equipment back together after the repair so that it is as safe and as reliable as it was when new. Careless assembly causes new faults such as trapped wires, loose connectors and missing earth leads.

Good practice:

• Reassemble in the reverse order of dismantling, using notes or photographs taken during dismantling.
• Route wires and ribbon cables along their original paths, away from heat sinks, moving parts and sharp edges, and secure them with cable ties or clips.
• Press connectors fully home and make sure that their latches are closed.
• Refit every earth lead, shield and insulating sheet, because they are safety parts.
• Return each screw to its own hole and fit the correct length of screw, so that a long screw does not reach a component.
• Test the equipment with the cover open where it is safe to do so, and then close it and test again.

Final assembly, connectors, cable ties and cooling components are treated further in the chapter on assembling repaired equipment and appliances.

3.1.2 Disposal of waste materials

A repair produces waste: old batteries, scrap metal parts, plastic, damaged boards and trimmings. Some of it is hazardous because it contains lead, acids or other toxic substances, and some can be recycled for its metal. Disposal is planned as part of the job. The waste is sorted at the bench into separate labelled containers, kept in a closed area away from the work, and collected by a licensed handler or a recycler. In Kenya the Environmental Management and Co-ordination Act, 1999 and the Sustainable Waste Management Act, 2022 set the duties for those who generate and handle waste. Waste is never burned in the open, buried in the compound or put in the general bin when it is hazardous.

3.1.2.1 Old batteries

Used batteries are hazardous waste. Lead-acid batteries contain lead and sulphuric acid, nickel-cadmium cells contain cadmium, and lithium-ion cells can catch fire if they are crushed, short-circuited or overheated.

• Batteries are collected in a dry, non-metal container, with lead-acid batteries upright so that they cannot spill.
• The terminals of small cells and lithium batteries are covered with tape, so that they cannot short against each other.
• A leaking battery is handled with gloves and eye protection, and is placed in a plastic container.
• A swollen or hot lithium cell is isolated outdoors on a non-flammable surface, and is passed to the recycler promptly.
• Batteries are handed to a recycler or to the supplier that takes back old batteries, and are never thrown into a fire or a general waste bin.

3.1.2.2 Lugs and screws

Lugs, terminals, nuts, screws and washers are small metal parts that accumulate during repairs. A crimped lug is not reused, because the crimp cannot be reopened and the joint would be weak. Screws, nuts and washers that are undamaged are reused after they are sorted into labelled trays by type and size, and the rusted, stripped or bent ones are scrapped. Scrap is separated by metal: brass and copper lugs from steel screws, and the collected scrap is given to a scrap metal dealer for recycling. Because small sharp parts can injure those who handle waste, the scrap is kept in a closed container.

3.1.2.3 Tapes

Insulating tape and other adhesive tapes are used up on every job, and the scraps and empty rolls become waste. Most insulating tape is made from PVC, which gives off harmful fumes when it burns, so the scraps are never burned. Used tape and rolls are collected with the other plastic waste and passed to a collector, or to the general waste if the contractor does not collect plastic separately. Tapes contaminated with solvents or adhesives are kept apart from the other waste.

3.1.2.4 Cable sheaths

When cable ends are stripped, the sheath and the insulation fall away as plastic waste, and most of it is often PVC. The plastic is separated from the copper, because the copper has value as scrap and the plastic does not. The insulation is collected in a labelled bin for plastic recycling, and it is never burned to recover the metal. Burning PVC releases toxic fumes and leaves harmful residues. Short lengths of stripped copper are kept in a separate tray and sold with the metal scrap.

3.1.2.5 PCBs

A faulty printed circuit board is electronic waste. It carries solder that may contain lead, flame retardants in the board material, and metals such as copper, tin and small amounts of gold. For that reason a board is neither put in the general bin nor burned to recover metal, because burning gives off poisonous fumes. Boards are placed in a labelled container for electronic waste, and they are handed to a licensed e-waste recycler or to a collection point. Components that are still sound and can be tested are salvaged for reuse. Old electrolytic capacitors and similar parts go in the same container.

3.1.2.6 Off cuts

Off cuts are the trimmings produced during a job, such as clipped component leads, short pieces of wire, cable ties, sleeving, and solder cuttings. Clipped leads are collected by shielding the cut with a finger or a guard, and any that fall are swept up with a brush or picked up with a magnet. Solder cuttings may contain lead and are treated as hazardous waste. The metal off cuts are kept in a tray and sold as scrap, and the plastic off cuts go with the plastic waste. A bench kept free of trimmings is also safer, because a loose lead can enter the eye or the skin and can short out a live board.

Chapter Summary

This chapter explored the essential maintenance activities involved in the repair and replacement of faulty components in electrical and electronic equipment. It detailed specific tasks such as cleaning, tightening, soldering, and assembling, which are fundamental to ensuring the proper functioning and longevity of appliances. The chapter also emphasized the importance of responsible disposal of waste materials generated during maintenance, including old batteries, lugs, screws, tapes, cable sheaths, printed circuit boards, and off cuts, to minimize environmental impact. Additionally, it covered key Environmental Health and Safety (EHS) regulations that guide safe work practices and environmental protection during maintenance operations. The chapter concluded with an overview of the Occupational Safety and Health Act (OSHA) regulations, highlighting the legal requirements for maintaining a safe and healthy workplace in the electrical and electronic repair sector. Together, these topics provide a comprehensive understanding of how to perform maintenance activities effectively while adhering to safety and environmental standards.