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Crypto Miners Direct

Buying guide

How to Inspect and Test a Used ASIC Miner

Inspect a used or refurbished ASIC miner on delivery, run an acceptance test under your own conditions and keep the evidence a claim needs.

Last reviewed October 5, 2026 by James Emerson

A used miner is accepted or rejected in the first days after delivery, and what you record then decides whether a claim succeeds. Inspect it before plugging it in, confirm at power-on that every hashboard and fan reports, then run it under your own conditions against the manufacturer's rated hashrate and tolerance. If a unit fails, contact the seller rather than opening it.

Key points

  • Know when the claim window ends before delivery. Some count from dispatch, not arrival.
  • Do not power on a unit with visible damage, loose heatsinks, corrosion or a damaged power supply.
  • Save photos, screenshots and the full log before any reset or firmware change.
  • Judge hashrate on a post-warm-up average against the exact model version's rated figure and tolerance.
  • Do not open a failing unit; opening can affect warranty and weaken a claim.

Before the delivery arrives

Get in writing the dead-on-arrival (DOA) window, the period in which a unit that fails on arrival is repaired or replaced, plus its start date, the evidence required and who pays return freight. For its own sales, Bitmain accepts DOA cases only within 30 days of the order's ship-out date, and transport damage within 14 to 30 days of dispatch depending on the courier. A used seller's terms will differ.

Prepare:

  • The yardstick. Get the rated hashrate, power and tolerance for the exact model and hashrate version from the manufacturer. Bitmain's Antminer S21 XP specification, for example, gives typical values at 25 °C inlet air, with actual hashrate varying by ±3% and power by ±5%.
  • Warranty status. Bitmain counts warranty from its official dispatch date, subject to the sales contract, and offers a serial-number check. Transfer to a second owner depends on the manufacturer's terms.
  • Power. The circuit and cords must suit the miner's continuous load and be installed by a qualified electrician; see Bitcoin Miner Power Requirements. An illustrative 3,500 W unit uses 3.5 kW × 24 h = 84 kWh per test day; see the electricity cost calculator.
  • Network. Wired Ethernet; Bitmain warns that Power over Ethernet switches burn out its control boards.

Receiving and unpacking

How to Buy ASIC Miners Wholesale covers counting cartons and noting damage on the receipt. Also:

  1. Before opening, photograph any carton that is wet, crushed, holed or dented, as Bitmain advises.
  2. Report transport damage to the carrier promptly. Bitmain wants the carrier claim filed first; ask what your seller requires.
  3. Photograph each unit's serial and model labels and its power supply (PSU) label. Keep the packaging until testing ends.

A unit shipped through freezing weather can be well below 0 °C inside. Bitmain's cold-region guidance is to warm it in a dry area for 30 minutes so moisture disperses, and not to start air-cooled Antminers below 0 °C. Your model's specification governs.

Physical inspection before power-on

Bitmain and MicroBT both say to check for damage before power-on, and Bitmain says not to use a miner that appears damaged. Inspect without removing covers.

Check What to look for If found
Case Dents and cracks, especially at corners Photograph and report
Fans Broken blades, damaged cables. Each should turn freely by hand Do not power on
Heatsinks Shake gently and listen. Bitmain says slight board movement is normal; an abnormal sound can mean heatsinks have come off Do not power on
Visible connectors Bent pins, scorching, melted plastic Do not power on
Corrosion and residue White, green or rust-coloured deposits, or an oily film Report and ask about the unit's history
Labels Serial and model labels present, legible, matching the order Report. MicroBT's warranty excludes products with altered or removed labels
Power supply Correct model for the miner, no damage Do not power or open a damaged PSU

Bitmain classes corroded boards as scrap it will not repair; treat corrosion as a claim.

First power-on

  1. Connect the power cord to the miner, then to the socket, as MicroBT instructs. With a separate PSU, Bitmain says to power hashboards before the control board.
  2. Watch the start-up. Every fan should spin. In Bitmain's 17-series example, normal running shows the red light off and the green light flashing; both flashing means hashrate below 90% of normal. Other models differ.
  3. Find the IP address with the manufacturer's tool, such as Bitmain's IP Reporter or MicroBT's WhatsMinerTool.
  4. Save the evidence listed under Records below before changing anything.
  5. Check that the model the interface reports matches the label and order. Bitmain has warned of a scam in which an older model was sold as a newer one.
  6. Check the pool settings. Bitmain describes compromised miners mining to pools their owners never set, and recommends a factory reset and new password. Load no unofficial firmware without the seller's written agreement; Bitmain voids warranty for firmware-caused malfunction.

Status page pass criteria

Field names vary by firmware; Bitmain's S19 guide shows chips per chain and a chip-state icon.

What to read Pass on delivery Fail or query
Hashboards Every board the model has, each hashing A board missing or at zero
Chips per board, where reported The documented count for the exact model, consistent with the other boards Short count, or chips marked abnormal
Fans All detected, similar speeds Missing, zero or erratic
Temperatures Similar across boards, below the model's limit One board far hotter than the rest
Log No repeating errors Repeating board, fan, power or temperature errors

Ignore early hashrate. MicroBT says WhatsMiner units run a frequency search of about 40 minutes after power-on, during which hashrate reads low.

The acceptance run

A unit healthy at ten minutes can still fail; Bitmain describes hashboards dropping to zero after running for a while. Test every unit, or the sample your contract allows, on your own circuit, network, pool and intake air.

No manufacturer source cited here sets a buyer's burn-in duration. Pick one that starts after warm-up, covers your site's warmest hours, lets the pool average settle and leaves time to report, usually at least a full day per unit. That is a judgement, not a manufacturer rule; agree it with the seller.

Record machine and pool average hashrate for the same period, board temperatures, fan speeds, restarts, intake temperature, and power draw if your PDU meters it.

In this illustrative batch, units are rated at 200 TH/s ±3%, a band of 200 × 0.97 = 194 to 200 × 1.03 = 206 TH/s.

Unit Boards hashing Average hashrate % of rated Result
A 3 of 3 201 TH/s 100.5% Pass
B 3 of 3 192 TH/s 96.0% Below band. Check intake air, network and pool figure, then retest
C 2 of 3 133 TH/s 66.5% Fail. Report
D 3 of 3, one short of chips 180 TH/s 90.0% Fail. Report

A shortfall with every board healthy often has an outside cause; Bitmain attributes many low-hashrate cases to network instability and high pool rejection. If B reaches the band once that is fixed, it passes. If not, report both runs.

Records for a claim

Keep one folder per serial number. Bitmain's DOA process asks for photos of the serial tag and screenshots showing the fault. Collect:

  1. Photos of packaging, damage, every serial and model label, and the PSU label.
  2. Screenshots of the status pages as the unit arrived: model, firmware version, boards, chips, fans, temperatures.
  3. The full log from start-up, saved as a text file named by serial number.
  4. The pool's hashrate chart for the acceptance run.
  5. Dates of delivery, testing and your report, with intake temperatures.

Log a batch in one spreadsheet by serial number.

When to stop and contact the seller

Report in writing, with evidence, if:

  • the unit is damaged, rattles, smells burnt, or shows corrosion or liquid;
  • a board is missing, short of chips or at zero, or a fan reads zero;
  • the reported model differs from the label or order;
  • the interface is locked, or the unit mines to a pool you did not set;
  • hashrate stays below the band after intake air and network are ruled out;
  • a breaker trips. Have a qualified electrician check the circuit; never fit a larger breaker or bypass protection.

Do not open the unit, move hashboards between units or restart it repeatedly. Bitmain warns that repeated restarts can make a repairable fault unrepairable, and treats a machine with non-original boards as mixed-board, which voids warranty. MicroBT excludes damage from unauthorised disassembly. Send claims only to confirmed contact details; for this site, see Verification. Once the claim is settled, Hashboard Troubleshooting and ASIC Fan Replacement cover repairs.

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