What parts wear out in hi-fi electronics?

Wearable parts come in the form of mechanical and electronic components.

Capacitors are common wearable electronic parts, specifically wet aluminium electrolytic types. Wear rates vary enormously according to type, heat soak and hours of use. I see capacitors fail in gear after 5 years and yet older parts that are still perfect at 50 years of age.

Transistors, diodes and resistors can also fail, this tends to follow certain types, fault scenarios and excessive heat exposure. Testing is the only accurate way to determine wear. Worn parts can be replaced with high-quality new ones.

Switches, potentiometers and connectors are the most common mechanically wearing parts. This includes rotary and linear controls and switches, speaker terminals, RCA connectors and so on. Many of these are serviceable and can be brought back from non-functional to working perfectly, with the correct service techniques. Other parts like connectors can be replaced with new parts.