Avalon 1246 – ASICCRC Error

Hard power-cycle at the breaker for a full 60 seconds — not a soft dashboard reboot. The MM3.1 firmware's CRC-error state can wedge after an unclean shutdown or a failed flash, and a cold-boot clears it more reliably than any soft restart. Count to 60 so the bulk capacitors fully drain before you power back up. On any 1246 running continuously longer than 90 days this occasionally clears a persistent `ASICCRC` warning on its own.

Visually inspect the chassis: confirm all three hashboard status LEDs on the MM3.1 show solid green at idle, verify no debris has worked into the air intake during transport or install, and listen for ticking or buzzing from the PSU during steady-state hashing. This sets your baseline before you change anything — if one of these is off you are chasing a different problem than `ASICCRC`.

Clean the air intake filters with a shop-vac and wipe the front grille with a lint-free cloth. Dust on the intake raises inlet temp 2-6 C and `ASICCRC` rates on 1246 units track directly with chip junction temperature. A cleaner intake can clear a marginal CRC warning entirely, especially during seasonal transition weather when ambient climbs unexpectedly.

Verify intake ambient temperature with an IR thermometer at the front grille (not room-middle). Target ≤ 30 C for a Canadian home or garage install, ≤ 35 C absolute max for any install. Above 35 C the A3206 bus margin closes fast and `ASICCRC` becomes progressively more likely — the data-centre-grade 40 C spec does not hold in residential deployment.

Check your MM3.1 firmware build at avalonminer.org/firmware-document/. If your build is older than the current stable for your hardware revision, plan a firmware upgrade — but only after you have cleared the hardware-side causes in Tiers 2 and 3. Flashing while a hardware fault is present means diagnosing two problems instead of one, and 1246 flashes are slower and more fragile than they look.

Power off at the breaker. Re-seat both ribbon cables on the hashboard flagged in diagnostics. Pull each connector fully, inspect the IDC contacts for blackening or oxidation, wipe with 99% isopropyl alcohol on a lint-free wipe if needed, then reseat until the latch clicks positively. This single step clears a majority of 1246 `ASICCRC` tickets in D-Central's repair queue — ribbon contacts are the A11/A12 family's known weak point.

Multimeter on DC, probe at the PSU-to-hashboard connector while the miner hashes at full nameplate power. Expect ~12.0 V sustained; anything below 11.6 V under load means a tired PSU or undersized circuit. If the rail is borderline swap with a known-good Canaan-spec APW-series PSU — never a generic PC PSU, the current-delivery envelope for sustained 3200 W is wrong for consumer hardware.

Measure line voltage at the service panel under full miner load. Expect 235-245 V on 240 V split-phase, 202-212 V on 208 V commercial. Low line voltage forces the PSU to draw more current, which amplifies rail sag, which amplifies bus ripple, which drives `ASICCRC`. If line voltage is chronically low, stop — this is an electrical-panel problem before it is a miner problem and the electrician call is cheaper than the repair.

Label the three hashboard slots 0, 1, 2 with tape. Physically swap the suspect board into a different slot and boot; monitor `kern.log` for 15 minutes. If `ASICCRC` follows the board, the board is the problem. If it stays in the original slot, the MM3.1 control board, the AUC3 interface IC, or the slot-specific backplane wiring is the problem — escalate to Tier 3 or Tier 4.

If you are running a non-default cgminer configuration (inherited unit, custom overclock, imported profile), reset the AUC3 flags to Canaan stock: `--avalon7-aucspeed=400000 --avalon7-aucxdelay=4000` with no explicit frequency override. Aggressive AUC3 tuning is a common undocumented failure mode after a profile import and is worth checking before you touch hardware on an imported 1246.

Connect to the miner API on port 4028 or SSH in and dump per-chain `ECHU`, `ECMM`, `MW`, and `PVT` arrays with `echo -n '{"command":"estats"}' | nc 127.0.0.1 4028`. Save the output to a file before you change anything else. This snapshot is what D-Central's repair bench will ask for if the fix ends up shipping to us — capturing it up front saves bench diagnostic time, which saves you repair dollars.

Replace the data ribbon cable on the affected chain with a new or known-good cable. Canaan IDC-style ribbons are available from D-Central parts, aftermarket from Zeus, or can be re-crimped locally with a proper IDC press. A vise-grip hand re-crimp usually works for a few weeks and then fails again — order a proper ribbon unless you are in a parts-shortage emergency.

Remove the heatsinks from the affected 1246 hashboard. Inspect for dried thermal paste, crumbled thermal pads, and pad-liquid migration especially on the PCH and voltage-domain ICs. Re-apply Arctic MX-6 or Thermal Grizzly Kryonaut in a thin uniform layer; replace any crumbled pads with fresh ones at the correct thickness. Dried pads under the PCH are a silent cause of `ASICCRC` on 1246 units older than 18 months — the bus driver sits directly under that package.

Reflow the single worst-performing chip from diagnostic Step 5 with preheat plus hot-air: preheat from the bottom at 150 C, apply top-side hot-air at 310-330 C for ~30 s, natural cool-down, fresh paste on reassembly. The A3206 BGA tolerates one reflow cycle well. A second reflow on the same chip within 90 days rarely holds — at that point replace the chip, do not reflow again.

If your MM3.1 build is known to exhibit strict-CRC behaviour (check release notes on the Canaan firmware portal — sparse but dated), roll back one build using the AUC3 flash interface and Canaan's official flash utility. Verify your board hardware revision against the firmware compatibility table before flashing. Wrong firmware for a late-revision 1246 control board will brick the MM3.1 and add a Tier 4 repair to your existing problem.

Inspect capacitors and MLCCs near the PMIC and AUC3 interface IC on both the affected hashboard and the MM3.1 control board. Bulging electrolytics, cracked MLCCs, or discolored board near a passive means stop and replace before running the miner again. A failing cap near the bus driver shows up as `ASICCRC` long before it manifests as a hard fail — running through the degradation accelerates adjacent damage.

Stop DIY and ship to D-Central when any of these are true: per-chip PVT isolates the same chip position on two different 1246 hashboards; a chip has been reflowed once and `ASICCRC` returned within 30 days; the MM3.1 control board is suspected; visible capacitor damage near the AUC3 interface IC; or any burnt-component smell during testing. Book a D-Central ASIC Repair slot at d-central.tech/services/asic-repair/ — 5-10 business days, Canada / US / international.

Pack hashboards in anti-static bags, double-box with ≥ 5 cm of foam on every side, and include a printed note with: the exact `ASICCRC` lines from `kern.log`, your MM3.1 firmware build string, PSU model and measured rail voltage, ambient at install, and all Tier 1-3 steps already run. This saves D-Central bench diagnostic time which saves you repair dollars. Bench process for a CRC-suspect 1246: AUC3 bus isolation on a test fixture, chain-by-chain CRC replay, chip replacement with graded A3206 parts, reflow and re-seal, 24 h nameplate burn-in with log capture.