Guides / Buying
What to check before buying a used synth
A 15-minute check that catches most problems with second-hand synths, drum machines and grooveboxes. Updated September 2026.
The short answer: power it with the right supply, play every key, move every control, check the screen and outputs, and ask about the battery and firmware. Most faults show up in ten minutes.
Before you go
- Know exactly what it is. Many synths have versions at very different prices: a Minilogue and a Minilogue XD, an SP-404 and an SP-404 MKII, a Digitakt and a Digitakt II. Check the model name on the unit, not just the listing title.
- Know what it's worth. Look up recent sold prices, not asking prices. Our price guide covers popular models, including the Korg Minilogue XD and Arturia MicroFreak.
- Ask for the power supply. Many synths use a specific voltage and polarity, and a missing or wrong supply is common. Allow for buying one if it isn't included.
- Bring headphones and a cable. Headphones let you test anywhere, and a jack cable lets you test the main outputs.
The 15-minute check
| Check | How | What a problem looks like |
|---|---|---|
| Power | Use the correct supply and switch on | Doesn't boot, restarts, or the power socket is loose |
| Every key | Play each key slowly, soft and hard | Dead or double-triggering notes, uneven velocity, clicking keys |
| Every voice (polysynths) | Hold a big chord, then play the same note repeatedly | One voice quieter, out of tune or silent |
| Knobs, sliders and encoders | Move each one through its whole range while a sound plays | Crackle, jumps, dead spots or values that skip |
| Buttons and pads | Press every one; hit pads soft and hard | Needs pressing hard, double-triggers, uneven pad response |
| Screen | Look at it straight on and at an angle | Dead pixels, faded backlight, missing segments |
| Outputs | Headphones, then the main outputs | Crackle when you move the plug, one side missing, hum |
| MIDI and USB | Connect to a phone or laptop if you can | Not recognised, drops out |
Analogue synths: let it warm up
Analogue oscillators drift until they're warm. Leave it on for 10-15 minutes, then check it holds its tuning. Many modern analogue synths have a tuning or calibration routine; ask whether it's been run, and whether it holds afterwards.
Older synths: the memory battery
Many older synths keep patches on a small internal battery. "Battery low" on start-up, or lost patches, means a cheap replacement. A leaked battery is different: walk away from any corrosion on the board.
Things to ask the seller
- Has it ever been repaired or opened?
- Which firmware version is it on? (Updates are usually free, but it tells you how well it's been kept.)
- Will the user sounds or patterns be wiped, or are they part of the sale?
- Is the original box included? It makes a big difference if you ever post it on.
Common faults and rough costs
- Dirty controls: often fixed with contact cleaner, a few pounds.
- Missing power supply: roughly £8 to £30.
- Dead keys, faders or screens: anything from a DIY job to a repair that isn't worth it.
The price guide lists usual faults and rough costs per model.
The flipper extension prices any Marketplace listing for you and flags faults the seller mentions. Free while in testing: join the testers.