⚡ Stored high voltage
fatal
Where you meet it: CRTs · microwave oven HV capacitors · PSU bulk capacitors · flyback transformers · any large oil-filled or motor-run capacitor
What you need to know
- A CRT holds 25–30 kV on the anode and recharges itself through dielectric absorption after you discharge it. Discharge through a series resistor to the dag ground, repeat, then leave a shorting strap in place while you work.
- Microwave oven HV capacitors can deliver a lethal shock months after unplugging. Discharge before touching anything in the cavity.
- PSU bulk caps (the big 200–450 V cans) likewise. Use a 1–10 kΩ, 5–20 W resistor across the terminals for 30+ seconds, then confirm with a meter.
- Work one-handed, other hand in your pocket, around anything undischarged — it keeps current from crossing your chest.
- Isolate and lock out. Never work on plugged-in equipment.
The rule: NEVER short a large capacitor with a screwdriver. It welds the tip, blasts molten metal at your face, and can rupture the can.
Components this applies to
Silver-Graphite Brushes & Slip Rings
Ag 40–95% by weightCu pigtail + commutator segmentsBase electrographite
S
Thermostats, Snap Discs & Limit Switches
Ag 0.4–1.6 g/lb as whole discs; 408–431 g/lb as harvested contactsBase bimetal steel discBase Hg ~3–4 g per bulb thermostat ampoule
B
Arcade PCBs / JAMMA Boards
Au 0.05–0.20 g per board ≈ 0.09 g/lbCu ~45 g/lbAu ceramic gold-lid customs (FD1094
C
Automotive relays & fuse boxes
Ag 25–80 mg per mini ISO relayCu 1–3 g coil + terminals per relay
C
Automotive wiring harness
Cu 48–52% recovery stripped; ~35% as-pulledAu under 0.1 g per whole vehicle
C
DC-DC converter bricks & isolation modules
Au 0.08–0.3 g/lbAg 1–4 g/lbCu ~90 g/lb
C
Enterprise Switches, Line Cards & Optics
Au 0.15–0.6 g per large line card ≈ 0.075 g/lbCu ~70 g/lbBase chassis backplane
C
EV / hybrid battery management boards
Au 0.01–0.05 g per master boardAg ~0.1 g per master boardCu 10–50 g busbar traces per cell-tap board
C
Hybrid / EV traction inverter ⚡
Cu 3–8 kg per inverterAg 0.5–3 g sinter per power stageAu 0.02–0.08 g on gate-driver boardsBase 5–15 kg aluminium housing
C
Instrument clusters & head units
Au 0.008–0.100 g per unitAg 0.2–0.6 g in a premium head unitPd 0.02–0.06 g in a premium head unitCu 20–500 g
C
Klystrons & Travelling-Wave Tubes
Cu ~250 g/lb (0.35–0.75 lb Cu per lb of tube)Au ~0.5–4 g per tubeAg 2–30 g per tube
C
Metal oxide varistors (MOVs)
Ag 6–14 g/lb
C
Xenon HID ballasts & LED drivers
Au 0.003–0.015 g per ballastCu 30–90 g in the HV transformer and inductorsAg trace in thick-film and solder
C
Aluminium electrolytic capacitors
Base aluminium can
D
CRT flyback transformers & deflection yokes ☠
Cu 150–400 g per yokeBase ferrite core
D
Laser Printer Boards, Fusers & Toner Chips
Au 0.01–0.04 g per formatter board ≈ 0.045 g/lbAu 0.0005–0.002 g per toner CRUM chip ≈ 0.3–0.8 g/lb of chipsBase Fuser: no precious metal whatsoever
D
LCD Panels (ITO / CCFL vs LED)
Base Indium ~0.4–0.8 g/m² of ITO layerAu 0.01–0.08 g per panel in COF tape bumpsCu ~17 g/lb
D
Low-grade boards (PSU, TV, modem, appliance)
Au 0.005–0.05 g/lbAg 0.2–0.8 g/lbCu 8–15%
D
Magnetron ☣☣
Ag 0.5–2 g per magnetronCu 200–400 g per unitBase ferrite magnets
D
Nixie Tubes, VFDs & Dekatrons
Base nickel cathodesBase tungsten filament (µg) in VFDsBase total metal value $0.02–0.15 per tube
D
Photomultiplier Tubes (PMTs)
Ag 0.1–2 g per tubeAu 0–20 mg per tubeBase BeCu dynodes with an activated BeO surface
D
Power supplies
Au 0.005–0.03 g/lbCu 30–60 g per transformerAg in the relay
D
Spark plugs
Pt 1–8 mg per plugBase iridium 0.6–3 mg on Ir plugs
D
Vintage Home Computers & Boards
Au 0.05–0.20 g per C64 board; 0.1–0.4 g per Apple II boardAu gold-lid ceramic DIPs at $150–400/lbCu ~40 g/lb
D