Check the serial number before you buy that used console

The single most useful thing you can do before buying a second-hand console is look up which revision you're being offered. A launch PlayStation 4, the CUH-1000 model that shipped in 2013, runs hotter, sounds like a hairdryer under load, and has a well-known weak spot in the HDMI port. A CUH-2000 slim from a few years later does the same job, quieter and cooler, and often sells for the same money because most sellers don't know the difference. The model number is printed on a sticker on the back or underside. Ask for a photo of it before you agree to anything.

That one habit filters out most of the duds.

Buy the later revision, every time

Console makers spend the first two years of a generation fixing what they got wrong. You want the machine they fixed.

The Nintendo Switch is the clearest case. The original model and the revised one look identical on the shelf, but the revision is HAC-001(-01) and gets noticeably longer battery life. The box has a red background behind the console instead of a white one. If you're buying boxed, you can tell across the room. If you're buying loose, the model number is printed in tiny text on the back of the unit under the kickstand.

Xbox 360 is the other one people get burned on. The early white units had the overheating failure everybody remembers. The later S and E models redesigned the cooling and the failure rate dropped off a cliff. If someone's selling you a white 360 with a bulging case and a story about how it "just needs a reflow", walk.

Original Xbox is a special case worth knowing about if you're going retro. Early units have a clock capacitor on the motherboard that leaks over time and eats the board it's sitting on. Plenty of otherwise-fine consoles have been killed by it. If you buy one, opening it up and removing that capacitor is a known, well-documented job. The console keeps working, it just forgets the date.

The ten minutes that matter

Never buy a console you haven't seen running. Not "the seller says it works". Running, in front of you, on a screen.

When you get there:

• Power it on cold. Listen. A fan that screams from the first second usually means years of dust and a dried-out thermal paste job. That's fixable, but it's a bargaining point.
• Put a disc in, if it has a drive. Take one with you. You want to hear it spin up, read, and load. Grinding, repeated seeking, or a disc that ejects itself is a dying laser.
• Wiggle the HDMI cable at the console end while a game's on screen. Flicker means a loose port, and a loose port means soldering.
• Check every USB port with a controller cable.
• Open the settings and look at the storage, the system update status, and whether it's connected to the internet. A console that refuses to go online may be banned rather than broken.
• Smell it. Smoke and pet hair get pulled straight through the fan and cake the heatsink. You'll be opening that machine up within a month.

If the seller won't let you do this, there's a reason. Say thanks and go.

Controllers are the consumable, not the console

Consoles mostly keep working. Controllers don't.

Analogue stick drift is the default failure on every modern pad. Test it properly: go into the system's controller settings or calibration screen, let go of both sticks, and watch whether the cursor sits still. Then push each stick to all four extremes and listen for grinding. Do the same with the triggers and shoulder buttons.

Joy-Cons deserve extra suspicion. Drift on those is so common that Nintendo has run a repair program for it in several regions. Check what's currently offered in your country before you assume a drifting pair is worthless, because it may be a free fix and a decent discount.

Budget for a spare pad. A console with one tired controller is a one-player console.

Handhelds have their own list

Push gently on the back of the battery cover on any handheld older than about ten years. If it bulges, the lithium cell is swelling, and that's the one repair you shouldn't put off. Swollen batteries crack shells and eventually vent.

On a Game Boy Advance SP, lift the battery cover and read the model number. AGS-001 is the dim front-lit screen. AGS-101 is the bright backlit one, and it's worth real money more. Sellers list both as "GBA SP". Ask for the photo.

On a DS Lite, look at the hinge. They crack, always on the same side, and once it goes the top screen ribbon follows.

On a 3DS or a Wii U, ask whether the Nintendo Network ID has been removed and the system formatted. Buying one with somebody else's account still on it's a headache you inherit permanently.

Discs, cartridges and the fakes

Hold PlayStation 1 and early CD-format discs up to a bright light with the label facing you. Pinholes of light through the reflective layer mean disc rot. Nothing fixes it.

Radial scratches, the ones running from center to edge, are worse than circular ones. Deep scratches can be resurfaced at most game shops, but resurfacing shaves material off and you only get a few goes.

Cartridges are where the fakes live. Pokémon is the most counterfeited game family on earth, and the copies have got good. Three checks that still work:

Turn the cartridge over and look at the screw. Genuine Nintendo carts use a tri-wing screw, the one with the three-pointed Y-shaped head. A Phillips screw is a repro shell almost every time.

Look at the label printing under a phone camera zoom. Real labels are sharp. Fakes often show dot-matrix printing and slightly wrong color saturation, and the label edges sit flush rather than slightly raised.

For the Game Boy Advance Pokémon games, ask whether the in-game clock works. Ruby, Sapphire and Emerald have an internal battery for real-time events like berry growth. Many fakes have no battery at all, and a lot of genuine carts now have a dead one, which is a cheap replacement rather than a dealbreaker.

Where you buy changes what you're buying

CeX and similar high-street resellers charge more, and in exchange you get a warranty measured in months or years rather than a phone number that stops answering. Check the current terms rather than taking my word for the length. For anybody who doesn't want to test things themselves, that markup is the cheapest insurance in gaming.

eBay sits in the middle. You lose the hands-on test, but "item not as described" gives you a real route back. Photograph the parcel as you open it.

Local marketplace listings are where the bargains and the burns both live. Cash, in person, after the ten-minute test. If a seller pushes for payment before you meet, that's the end of the conversation.

One case for buying the dud on purpose

If you're handy, a console listed as faulty for a specific, named reason is often the best value on the site. A PS4 with a dead disc drive still plays a digital library. A console that "won't read discs" frequently needs a laser ribbon or a deep clean. A fan that howls usually needs forty minutes, a screwdriver set and fresh thermal paste.

The faults worth avoiding are the vague ones. "Sometimes won't turn on" means a fault nobody could find.

Last thing. Ask the seller why they're selling it, and listen to how fast the answer comes. "Upgraded to the new one, it's just sat in the cupboard" arrives instantly. The pause before the story is the tell.