Buying Used ASICs: How to Spot a Deal and Avoid Scams
Brand new ASIC miners are expensive. An Antminer S21 can cost thousands of dollars. For many home miners, the entry point is the second-hand market (eBay, Telegram groups, or hardware brokers).
You can find amazing deals—like an Antminer S19 for under $1,000—but you can also buy a glorified paperweight. Mining hardware degrades over time due to heat and vibration. Here is how to inspect a used machine like a pro.
1. The Physical Inspection (If buying in person)
- Shake Test: Pick up the miner and gently shake it. If you hear something rattling inside, it usually means a heatsink has fallen off a hashboard. Walk away. This is fatal damage.
- Fan Check: Spin the fans with your finger. They should spin freely and silently. If there is resistance or a grinding noise, the bearings are shot. (Fans are cheap to replace, but use this to negotiate a lower price).
- Port Check: Look at the Ethernet port and the 6-pin power connectors on the hashboards. Are they brown or melted? Burn marks indicate the machine was run way too hot or with bad cables.
2. The Dashboard Check (The "Kernel Log")
Never buy a machine without seeing it run for at least 30 minutes. Ask the seller for a screenshot of the Kernel Log or the Status Page.
- Look for "x" vs "0": On an Antminer status page, you will see a string of OOOOOOO. If you see XXXXXXX, those chips are dead.
- Chain Balance: An S19 has 3 hashboards. Ensure all 3 are showing up. If only 2 are showing, the machine is broken.
- Temperature: If the board temps are vastly different (e.g., Board 1 is 60°C, Board 2 is 85°C), the thermal paste is bad or the airflow is blocked.
3. The "Refurbished" Trap
Be careful with machines sold as "Refurbished" from China.
Often, these are machines that died in a massive farm, were hastily repaired with mixed components, spray-painted to look new, and sold to foreigners.
- Sign of a Refurb: Look at the screws. If the warranty stickers are broken or the screws are stripped, it has been opened.
- Mixed Hashboards: Check the serial numbers in the software. If the hashboards have wildly different frequencies, it’s a "Frankenstein" miner built from spare parts.
4. Safe Payment Methods
If buying online:
- NEVER pay with direct Crypto (USDT/BTC) unless you trust the seller 100%. Once sent, it is gone.
- Use Escrow: Use a trusted middleman service or a platform with buyer protection (like eBay or PayPal Goods & Services, though fees are higher).
Conclusion
Buying used is the smartest way to achieve a fast ROI (Return on Investment). A depreciated S19 mining on Gokby Pool earns the exact same Bitcoin as a brand new one, but costs half the price.
Just do your due diligence. Inspect the logs, check the temps, and never trust a deal that looks "too good to be true."
