{ "meta": { "title": "D-Central — Used-ASIC Condition-Grading Standard & Pre-Purchase Inspection", "description": "D-Central's 4-tier condition-grading standard (A / B / C / Parts) for used ASIC miners — what each grade means for hashrate, thermals, remaining life and a defensible warranty — plus a red-flag pre-purchase inspection checklist that deep-links the relevant D-Central reference for every check.", "generated": "2026-07-18T21:15:40+00:00", "as_of": "2026-07-18", "version": "1.0", "license": "https://creativecommons.org/licenses/by/4.0/", "license_name": "CC BY 4.0", "source": "https://d-central.tech/used-asic-condition-grading/", "method": "An authored standard, not measured data. Grades are D-Central's definitions, ordered by hashrate, thermals, remaining life and defensible warranty. The inspection checklist operationalizes the standard and links each check to the live D-Central reference (fault localizer, operating-temperature, PSU, fan-spec, firmware-lock, reliability index, used-price index). Nothing here is fabricated because the rubric IS the product.", "provenance": "D-Central repair-bench practice + the existing D-Central reference layer. Companion to /data/used-asic-price-index/ (price bands) and /data/asic-reliability-index/ (failure tiers).", "disclaimer": "A grading STANDARD, not an appraisal of any specific unit. Always verify a unit against the checklist yourself and match the price to the used-index band. Grades describe condition, not a guarantee of future performance." }, "grades": [ { "grade": "A", "name": "Excellent — near-new / low-hours", "hashboard": "All hashboards at or above the model's rated hashrate; zero dead chips; accept-rate normal; no board previously reflowed or repaired.", "thermal": "All chip temps in the healthy band under sustained load, even spread across the board (no hot corner); no evidence of past overheating (discoloured PCB, lifted heatsinks).", "cosmetic": "Clean, no immersion/oil residue, no corrosion, intact seals and labels, original PSU with matching hours.", "life": "Full remaining service life; typically <6 months runtime or genuinely refurbished to as-new.", "warranty": "A 30–90 day parts-and-labour warranty is reasonable and defensible.", "price": "Top of the used band — close to the used-price index high for the model.", "buy_for": "A buyer who wants a near-new unit and predictable life without paying new-unit lead times or price." }, { "grade": "B", "name": "Good — serviceable, moderate hours", "hashboard": "Within ~5% of rated hashrate; at most a small number of dead chips already compensated by autotuning; may have one professionally reflowed board that now passes.", "thermal": "Temps in the acceptable band; a slightly warmer board or a fan working harder is acceptable if hashrate and accept-rate hold.", "cosmetic": "Light wear, dust, minor cosmetic marks; no active corrosion; PSU healthy; seals may be broken from legitimate servicing.", "life": "Solid remaining life; the mainstream used unit — expect routine maintenance (fans, paste) over its remaining run.", "warranty": "A 14–30 day functional warranty (DOA-style) is defensible; full-term warranty is not.", "price": "Middle of the used band.", "buy_for": "The value buyer who accepts moderate hours and basic maintenance in exchange for a real discount." }, { "grade": "C", "name": "Functional — high-hours / as-described working", "hashboard": "Runs and hashes but below rated (dead chips, one weak board, or de-rated to stay stable); accept-rate acceptable but margins are thin.", "thermal": "Runs hot or needs elevated fan speed / lower power to stay stable; a hot board or uneven spread is expected and must be disclosed.", "cosmetic": "Heavy wear, dust, possible light surface corrosion; PSU may be aftermarket or high-hours; expect to service or replace fans and paste immediately.", "life": "Limited remaining life; best as a heat-reuse unit, a parts donor that still runs, or a cheap entry rig for a low-power tune.", "warranty": "Sold working / tested-on-arrival only — no meaningful warranty beyond DOA. Firmware unlock or repair may be needed.", "price": "Bottom of the used band.", "buy_for": "The heat-reuse or tinkerer buyer who wants cheap watts and can do their own maintenance." }, { "grade": "Parts / As-Is", "name": "Parts or as-is — not sold as working", "hashboard": "Does not reach a usable hashrate, has one or more failed boards, or is untested. Value is in salvageable boards, PSU, control board, frame and fans.", "thermal": "Not applicable — may not run, or runs only intermittently.", "cosmetic": "Any condition, including immersion units, water-damaged, or corroded.", "life": "None as a whole unit; value is per-component for repairs (cross-link the repair-parts and hashboard references).", "warranty": "None. Sold explicitly as-is / for parts, with no working claim of any kind.", "price": "Salvage value only — priced on recoverable components, not hashrate.", "buy_for": "Repair shops and DIY fixers sourcing donor boards, PSUs and control boards — never a first miner." } ], "checklist": [ { "group": "Identity & authenticity", "items": [ { "check": "Confirm the model and hashrate match the listing, and the serial/label matches the control board.", "red_flag": "Repainted shroud, mismatched labels, a serial that doesn't match the model, or a 'S19 Pro' that is really a plain S19 (114 vs 76 chips per board).", "why": "Model swaps and relabels are the most common used-market fraud. Cross-check the real spec before you pay.", "link": "/asic-hashboard-reference/", "link_label": "Hashboard reference (chips per board by model)" }, { "check": "Ask for a live screenshot of the miner's status page showing hashrate, per-board chip count, and temperatures under load.", "red_flag": "Seller refuses live proof, sends only stock photos, or the screenshot hides the chip/temperature columns.", "why": "A working unit can always show its own status page. No live proof is itself a red flag.", "link": "/miner-api-reference/", "link_label": "Miner API / status reference" } ] }, { "group": "Hashboard health", "items": [ { "check": "Compare actual hashrate to the model's rated hashrate, and check for dead or missing chips on any board.", "red_flag": "Hashrate well below rated, a board reading far fewer chips than spec, or frequent hardware errors in the log.", "why": "Dead chips and a de-rated board are the difference between a Grade A and a Grade C unit — and drive the repair cost you may inherit.", "link": "/hashboard-fault-localizer/", "link_label": "Hashboard fault localizer" }, { "check": "Look for evidence of prior board-level repair — reflowed chips, replaced components, flux residue.", "red_flag": "Undisclosed rework on a unit sold as Grade A; sloppy reflow or bridged pads (see the reball reference for what good work looks like).", "why": "A professionally repaired board can be fine, but undisclosed repair on a 'like-new' unit is misrepresentation and shortens life.", "link": "/asic-bga-reball-reference/", "link_label": "BGA reball & reflow reference" } ] }, { "group": "Thermal signs", "items": [ { "check": "Check per-chip temperatures under sustained load and confirm an even spread across each board.", "red_flag": "A hot corner or hot board, chip temps near throttle, or a discoloured/browned PCB from past overheating.", "why": "Uneven or high temps predict the next failure. A unit that only stays stable de-rated is a Grade C at best.", "link": "/asic-operating-temperature/", "link_label": "ASIC operating-temperature reference" } ] }, { "group": "Power supply", "items": [ { "check": "Confirm the PSU model matches the miner and the input voltage (120 V vs 200–240 V), and that it is the original or a proper equivalent.", "red_flag": "A 120 V-only PSU on a unit that needs 200–240 V, an aftermarket PSU with no spec, or scorch marks / a burnt smell around the connectors.", "why": "A wrong or failing PSU is a fire risk and a hidden replacement cost; APW12/APW17-class supplies are 200–240 V only.", "link": "/asic-psu-reference/", "link_label": "ASIC PSU reference" } ] }, { "group": "Fans & cooling", "items": [ { "check": "Confirm all fans spin freely, report correct RPM, and match the model's fan spec; listen for bearing noise.", "red_flag": "A seized, wrong, or noisy fan; RPM readings missing; fans running at 100% just to hold temperature.", "why": "Fans are consumable and cheap, but fans pinned at max to stay cool signal a deeper thermal problem.", "link": "/asic-fan-specification-reference/", "link_label": "ASIC fan-specification reference" } ] }, { "group": "Immersion & water damage", "items": [ { "check": "Inspect for oil/immersion residue, water staining, corrosion on connectors, or a cleaned-up ex-immersion unit sold as air-cooled.", "red_flag": "Oily film, white/green corrosion, or a suspiciously 'deep-cleaned' board — ex-immersion units are Grade C or Parts, never Grade A.", "why": "Immersion and water exposure change the remaining-life story entirely and must be disclosed and graded down.", "link": "/immersion-cooling-fluids/", "link_label": "Immersion cooling fluids reference" } ] }, { "group": "Firmware & lock status", "items": [ { "check": "Confirm the firmware is stock or a disclosed known build, and check whether the model/firmware is prone to vendor locking or bricking.", "red_flag": "A locked or unknown-custom firmware, a unit stuck in a bootloader, or a model on the firmware-lock tracker with an unresolved lock.", "why": "A firmware lock can turn a working unit into a repair job; know the lock status before you buy.", "link": "/asic-firmware-lock-tracker/", "link_label": "ASIC firmware-lock tracker" } ] }, { "group": "Expected reliability", "items": [ { "check": "Check the model's expected reliability tier and known failure modes for its generation before committing.", "red_flag": "A generation with a poor reliability record priced as if it were a safe long-life unit.", "why": "Some generations simply fail more; factor the model's reliability tier into the grade and the price you will pay.", "link": "/data/asic-reliability-index/", "link_label": "ASIC reliability index" } ] }, { "group": "Price sanity", "items": [ { "check": "Compare the asking price to the used-price index band for the model and condition, on a $/TH basis.", "red_flag": "A Grade C price attached to a Grade A claim, or an asking price above the used-index high for the model.", "why": "The grade sets the band: a fair used price tracks condition. Anything above the index high for the model needs justifying.", "link": "/data/used-asic-price-index/", "link_label": "Used-ASIC price index" } ] } ], "context": { "why": "The used-ASIC market is where a first-time buyer is most likely to get burned: a relabelled model, a de-rated board sold as full-hashrate, an ex-immersion unit deep-cleaned and sold as air-cooled, or a firmware-locked miner that becomes a repair job the week after it arrives. D-Central lives on the repair bench, so we know exactly what separates a good used unit from a bad one — and we have turned that into a public standard anyone can cite.", "standard": "The grading standard below is D-Central's own definition, not a measured dataset — which is precisely why it is trustworthy: there is nothing to fabricate. A grade is a promise about hashrate, thermals, remaining life and a defensible warranty, in that order. We hold our own refurbished inventory to it (\"graded to the D-Central standard\"), and we publish it openly so any buyer or seller can use the same yardstick.", "how": "Use it in two passes. First, run the pre-purchase inspection checklist — each item links the exact D-Central reference you need to judge it (fault localizer, operating-temperature, PSU, fan-spec, firmware-lock, reliability index). Then map what you found onto the grade table: the lowest criterion a unit meets is its true grade. A unit that hashes at rate but hides an ex-immersion board is not Grade A — it is Grade C with a disclosure. When in doubt, grade down and price to the used-index band.", "verdict": "Buy the grade, not the photo. Match the asking price to the grade's band on a $/TH basis, insist on live proof of hashrate and temperatures, and treat \"no live status page\" and \"recently deep-cleaned\" as automatic downgrades. A Grade A unit earns a real short warranty; a Grade C unit is cheap watts for a tinkerer or a heater; Parts is for donors only, never a first miner." } }