NerdQAxe – Chain Break / Missing ASIC Chips on Boot

Cold-cycle three times. Pull the 12V at the PSU and the XT30 / barrel at the miner. Wait 30 s. Power back. Boot. Capture chain count. Repeat twice more. If chain count is 4/4 on any of the three boots, the fault is intermittent - not fixed. Note the pattern (always 3/4? sometimes 3/4, sometimes 4/4?) and proceed accordingly. Stable misses point at hard joint failure or dead chip; wandering misses point at a temperature-sensitive cold solder.

Re-seat the heatsink with fresh thermal paste. Power off, disassemble, IPA-99% clean every chip top and the heatsink contact face, apply Arctic MX-6 (rice-grain dot per chip, spread by torquing the heatsink down evenly - not by finger), reassemble to spec torque. Cold-cycle and re-boot. Roughly 25% of chain-break units that hit D-Central's bench recover at this step because dry paste was lifting the heatsink and stressing BGA joints under thermal cycling.

Inspect the case and PCB for shipping damage. Drops bend boards, bent boards crack BGA joints. Look at the corners of the board, the screw mount points, and the chassis itself for any sign of impact or warp. If you see deflection, take photos before disassembling further - you may be filing a shipping insurance claim before continuing the diagnostic.

Confirm firmware is current and matches BM1368. In the web UI System Info panel, verify the firmware build targets BM1368 (not BM1366, not BM1370). Cross-flashed firmware can produce false chain-break readings because protocol framing differs between chip generations. Reflash the correct ESP-Miner-NerdQAxePlus build for BM1368 if needed. Cross-checking the silk-screen on the chips themselves confirms which variant you have.

Update to the latest stable firmware. Older builds had less detailed chain-init logging and occasionally false-positive chain-break detection. Pull the current release from the Bitmaker-Mining repository, flash via OTA or the NerdQAxe web flasher, factory-reset NVS, reconfigure WiFi and pool, retest. Some chain breaks resolve as a firmware regression.

Capture the full boot log. USB-C, 115200 8N1, terminal of your choice. Cold-cycle and capture the first 30 seconds to a text file. Look for: chain enumeration line (`BM1368 x N detected`), per-chip discovery messages, `timeout` or `no response` entries, and which chip number first failed. Save the log - if you escalate to D-Central or the NerdQAxe Discord, this is the first thing anyone wants.

IR-thermometer-walk the chip positions during a hash attempt. Power up, let the firmware try to hash for 60 seconds, point an IR thermometer at each BM1368 in sequence, log the temp. Healthy chips read 45-65 C at 60 s of attempted load. Dead/silent chips read ambient (20-30 C). Cross-check the cold chip's position against the boot log's missing-chip number - they should match.

Multimeter the local VCORE at each chip. Power up, probe each chip's bypass cap pad (or closest accessible test point). Expected: 1.05-1.15 V DC across all four chips. A chip reading 0 V or under 0.9 V while neighbours read 1.10 V has a local power-rail fault - flag for Tier 3/4. All chips reading nominal VCORE while one is silent points at silicon or joint failure.

Re-seat the suspect chip's decoupling caps. Visible damage to caps near the suspect chip is fixable with a hot-air station and replacement components - Murata or TDK MLCCs in the package size shown on the schematic. If you don't have rework gear, this becomes Tier 4. Don't try this with a soldering iron only; you'll damage adjacent components.

Test on a different PSU. Borderline-spec PSUs can produce intermittent chain breaks on units that pass quick checks. Swap to a known-good 12V / 10A brick for 30 minutes of boot cycles, log chain-init outcome each boot. If the chain comes up clean on the swap PSU, your original PSU is the culprit - power-rail noise was breaking chain enumeration timing.

Reflow the suspect chip with preheat + hot air. Disassemble. Flux the suspect BM1368 BGA from the side (no-clean flux wicks under the package via capillary action). Preheat the bottom of the board to ~150 C to reduce thermal shock. Top-side hot air at 310-330 C, slow circular motion, ~30 seconds total dwell. Watch for the package to settle - a tiny visible drop as solder balls reflow. Cool naturally on the preheat for ~3 minutes, then off. Re-paste, reassemble, cold-cycle. About 60% of cracked-joint chain breaks recover at this step.

Run a 24-hour burn-in after reflow. A reflow that holds for 5 minutes and fails again is a chip on the way out. A reflow that survives 24 hours of stock-clock hashing has a real shot at sticking around for 6-18 months. Run a serial-log capture overnight, watch for chain re-breaks. If it survives, you've bought months of mining for the price of a flux pen. If it fails within 24 hours, the chip is silicon-dead - move to chip replacement.

Scope the chain bus during enumeration. Trigger on the rising edge of the discovery command at chip 0's output. Verify clean digital signaling at every chip in sequence. A weak edge or excessive ringing at one chip's input suggests trace impedance issues or a partially-failing input stage on the receiving chip - both flag-able for Tier 4 if you're not equipped to repair traces or replace ICs.

Replace the suspect chip with a graded BM1368. D-Central stocks salvaged-grade and new-old-stock BM1368 chips for this repair; pricing is approximately $30 CAD per chip plus rework labour. Chip removal: hot air at 330 C, lift package with vacuum tool, IPA-clean residual solder. Chip placement: solder paste stencil, careful alignment to PCB pads, reflow with preheat plus hot air at ~330 C. This is bench-grade rework - if new to BGA work, practice on a Bitaxe Hex first.

Inspect the chain trace path with a USB microscope. Look for hairline cracks, lifted pads, tombstoned components, or solder bridges. PCB-level damage often hides at this scale. If you find a trace break, the fix is a jumper wire - 30 AWG enamel wire from upstream pad to downstream pad. Finicky but cheaper than replacing the board. Documented procedure on BM1368 boards is identical to the equivalent BM1366 Bitaxe trace repair.

Stop DIY. You've cold-cycled, re-pasted, scoped the bus, attempted a reflow on the suspect chip, and the chain still misses. OR you don't have hot-air rework gear and the issue is past Tier 2. OR you see PCB-level damage - burnt traces, lifted pads, missing caps. Stop. The NerdQAxe family is $200-$450 CAD hardware; sustained DIY beyond reflow can cost more in solder and ruined components than the bench fee. Book a D-Central NerdQAxe repair slot.

What D-Central does at the bench. Test fixture with controlled 12V rail and isolated VCORE monitoring. Per-chip enumeration verification with the open-source ESP-Miner test harness. Cracked-joint reflow with profiled preheat and hot-air. Chip replacement from D-Central's graded BM1368 inventory at ~$30 CAD per chip plus labour. Trace repair with 30 AWG jumpers when needed. Post-repair 24-hour burn-in at stock clock to verify the chain holds before the unit ships back. Typical turnaround 5-10 business days Canada-wide.

Ship safely to D-Central. Anti-static bag around the PCB. Bubble wrap around the bag. Rigid outer box with at least 5 cm of foam on every face. Include a one-page note: which chip count the boot log reports (3/4, 2/4, etc.), firmware version string, PSU spec, any history of OC sessions / drops / liquid events, your contact info. Photograph the boot-log capture and include it on a USB stick or as a printed page. The clearer your write-up, the cheaper your repair.