Synthesizers range from simple, robust digital boxes to complex analog instruments with dozens of points of potential wear - what to check depends heavily on the type, but some basics apply across the board.
Quick checklist
- Test every key, pad and control (knobs, sliders, buttons) for physical response - listen for scratchy pots or sliders, a common and usually fixable issue.
- Check all outputs (audio, MIDI, USB, CV/Gate if present) and confirm the unit powers on reliably, including after being left on for a while.
- Load and play several factory presets across different patch types to confirm the sound engine (or voice circuits, on analog gear) works consistently across the keyboard range.
- Ask whether the original power supply is included - many synths use proprietary supplies that are hard to replace if lost.
- For anything vintage (roughly 1970s-80s analog gear), see our separate article on capacitor, battery and chip aging risks specific to older instruments.
A synth that "mostly works" can still be a reasonable buy at the right price, but knowing exactly what doesn't work lets you negotiate accordingly rather than discovering it after the sale.
