Hazards
This index is for parts leaving a machine that is already dead. It is not a set of instructions for defeating a door switch, an overheat fuse, or a lid interlock on something that will be plugged back in. If a procedure is past what you have done before, that part stays in the machine and the machine goes to a recycler.
Volts: how hard the electricity is pushing, measured with the circuit powered and the probes in parallel. Ohms and continuity: measured with the part unpowered. A beep means a connection. OL or a 1 on the left usually means open, no connection. Amps need a different socket on many meters. Using the amp socket to measure volts blows the meter fuse.
Can kill
Wall voltage and stored high voltage can kill. If you have not done this work with someone who already knows it, leave the part in the machine and take the machine to a recycler.
Mains voltage
Line voltage, and the DC bus just after the rectifier, both kill. A disconnected cord is not a discharged supply.
Where you meet it. Anything with a mains plug: supplies, washers, microwaves, heaters, fluorescent ballasts, treadmill boards, UPS inverters.
What to do. Unplug. If there is a primary bulk capacitor, discharge it through a resistor and confirm near 0 V with a meter before touching the board. One hand in a pocket is a real habit, not folklore. Do not work on live mains to 'see if it still runs' on a cluttered bench.
Stored high voltage
Capacitors hold a charge with the cord in your other hand. Microwave HV capacitors, CRT anodes, xenon flash caps, and primary bulk caps are the usual ones.
Where you meet it. Microwaves (about 1 µF class, rated above 2 kV), CRT televisions, camera flashes, ATX and UPS primary capacitors (170 V or 325 V DC), CCFL inverters.
What to do. Assume it is charged. Bleed through a power resistor sized for the voltage, not through a screwdriver. Confirm with a meter rated for that voltage. A bleeder resistor printed on the board may already be open — that is why it still bites.
CRT implosion and anode voltage
The tube is under vacuum. A cracked neck or face can implode and throw glass. The anode cap holds tens of kilovolts for days.
Where you meet it. Old televisions and monitors, arcade cabinets, oscilloscopes.
What to do. Default is: do not open it. Recycle the set intact. The phosphor and the glass are leaded. This index does not treat a CRT as a donor for anyone who is not already qualified to discharge an anode.
CCFL backlight inverters
Old LCD panels use a cold-cathode lamp driven at about a kilovolt of AC. The inverter is small and looks harmless.
Where you meet it. Laptop screens and monitors from roughly the 2000s, some scanners.
What to do. Unplug and discharge before handling. Do not run the inverter on the bench with the lamp out. Prefer LED-backlit donors.
Fire
These start fires in a drawer or on a bench, not only inside the original machine. Lithium cells and defeated heater fuses are the usual stories.
Lithium-ion cells
A punctured, crushed, overcharged, or reverse-charged cell vents and burns hot enough to ignite the bench. Swollen pouches are already failed.
Where you meet it. Phones, laptops, cordless tools, vacuums, hoverboards, e-scooters, vapes, Bluetooth speakers, power banks.
What to do. No puncture, no bending, no solder on the cell can. Storage around 3.6–3.8 V. Recycle swollen or long-flat cells; do not 'boost' a cell that has sat under 2.5 V. Charge at CC/CV with a real charger, attended, off the sofa. Damaged packs live outside until they reach a recycler.
Heaters without their cutout
Nichrome and tubular elements are happy to start a fire if the thermal fuse or tip-over switch is left out of the new circuit.
Where you meet it. Heaters, dryers, kettles, hair dryers, toasters.
What to do. A salvaged element is reused with a thermal cutout in series, on a non-flammable mount, or not at all. A PTC ceramic element is the one that limits itself.
Poison or pollution
Not always a shock. Mercury, old tube glass, toner, and refrigerant are disposal problems. Intact and labeled is the safe condition.
Beryllium oxide in magnetrons
The white ceramic in a microwave magnetron can be beryllium oxide. Intact it is stable. Dust from cracking, sanding, or machining it is a permanent lung hazard.
Where you meet it. The magnetron tube only. The magnets around it are outside the ceramic.
What to do. Do not open, cut, grind, or smash the tube. Ring magnets can come off the outside. The tube itself goes out as e-waste, whole.
Mercury
A broken CFL, fluorescent tube, or old tilt switch releases mercury. There is no useful parts yield that justifies breaking one.
Where you meet it. CFL bulbs, fluorescent tubes, some pre-1990s thermostats and tip-over switches, a few old silent light switches.
What to do. Recycle intact. If a glass capsule is already in a heater you are parting, do not crack it; bag the switch and take it to household hazardous waste. Do not vacuum mercury.
Laser toner
Toner is a very fine plastic dust. It makes a permanent mess of a bench and is a lung irritant. The cartridge is not where the good parts are.
Where you meet it. Laser printers and copiers.
What to do. Pull the cartridge out sealed, bag it, and do not shake it over the work. The motors and supply are elsewhere in the machine.
Lead solder, leaded glass, lead-acid
Older boards are tin-lead solder. CRT glass is leaded. UPS batteries are lead-acid and full of sulfuric acid.
Where you meet it. Pre-RoHS boards, CRTs, UPS and alarm batteries, automotive batteries.
What to do. Wash hands. Do not eat at the bench. Do not inhale flux smoke; a small fan to the side beats hovering over the joint. SLA cells get recycled even if you wanted the inverter transformer — a cracked case leaks acid.
Cuts, pinches, burns
Magnets slam, sheet metal cuts, and heaters stay hot. Ordinary workshop injuries, which still count.
Extracted laser diodes
Inside a player the diode is a Class 1 product because of the optics and the power limit. Pulled out and overdriven, DVD and Blu-ray diodes are an eye hazard, including the infrared one you cannot see.
Where you meet it. CD, DVD, and Blu-ray pickups, laser printers, some barcode engines.
What to do. Do not look into the facet, do not aim it at a reflective bench, do not power it from a battery. If you cannot set the current, leave the diode in the pickup.
Strong neodymium magnets
Hard-drive magnets slam together hard enough to blood-blister skin and shatter into sharp chips. They also wipe media and bother pacemakers.
Where you meet it. Hard disks, speakers, magnetron rings, headphone drivers, laptop lid latches.
What to do. Slide, do not pry. Keep a wooden wedge. Store with a keeper and a label. Away from CRTs, cards, disks, and people with implanted devices.
Airbags and pretensioners
These are pyrotechnics. They are not relays and they are not 'just a squib to look at'.
Where you meet it. Steering wheels, dashboards, seats, seatbelt buckles. Often yellow connectors.
What to do. Do not probe, cut, or power yellow connectors. Leave the modules in the car and let a dismantler deal with them.
Not yours, or not legal to dump
A curb is not a shop. Some of these objects are still someone else's property, or they have to go to a proper recycling point.
Refrigerant
Venting refrigerant from a fridge, freezer, dehumidifier, or air conditioner is illegal in a lot of places and pointless for parts. The sealed loop is not a donor.
Where you meet it. Refrigerators, window ACs, dehumidifiers, some water coolers.
What to do. Do not cut tubing, do not crack the compressor. Fans, door switches, relays, and start devices that unplug from the compressor pins are fair. The machine still needs a certified recovery step before the steel is scrap.
Americium in ionization smoke alarms
Ionization alarms contain a small Am-241 foil. It is not a parts project. Opening the chamber contaminates your tools.
Where you meet it. Smoke alarms labeled ionization, americium, or Am-241. Often a trefoil symbol.
What to do. Do not open. Recycle through the program printed on the back or household hazardous waste. Photoelectric alarms are a different device and are the ones with a useful horn.