Understanding and Addressing L7 Diagnostic Logs and Errors

The Antminer L7’s kernel log is the fastest path to a diagnosis. Every line is tagged with a severity (level=notice, level=error, level=fatal), a process id (pid=), and — for hashboard faults — the affected chain (chain=0 upward). Read it from the miner’s web dashboard under the kernel/system log, or over SSH. The L7 is a Scrypt machine on Bitmain BM1489 chips (120 per chain), so its strings reference LTC. The patterns below map each message to what failed and whether it’s a field fix or bench work.

Before you open the case: unplug the miner and give the PSU a few minutes to bleed down. The low-voltage board bus (single-digit through low-teens volts) is not a shock hazard, but the mains-side capacitors inside the APW12-class supply hold roughly 400 V for minutes after power-off. The L7 is a 200–240 V machine that will not run on 110/120 V household power, so treat the PSU as live and never open it. Hashboard faults carry a chain= index; connectivity faults carry a poolno= or net/stratum string — sort which family you’re in before pulling any board.

Fan error — “ERROR FAN LOST: fan lost”

The controller polls each fan’s tachometer. A reading of 0 RPM, or a speed that diverges sharply from its sibling, drops the fan out — and because the L7 won’t run without adequate airflow, it usually halts hashing.

1. Power down, then confirm the 4-pin fan connector is fully seated on the control board.
2. Spin the fan by hand: grinding, wobble, or a seized bearing means replace it.
3. Swap the suspect fan onto a known-good header to see whether the fault follows the fan or stays with the port.
4. Replace with a matching 12 V 4-wire PWM fan. A fan that spins but cannot report RPM — a 3-wire fan or one with no tach line — will trip the same “fan lost” error.

Temperature reading error — “temp lost”

A line such as level=error pid=865 chain=2 error="temp lost" msg=check_temp means the temperature sensor on that hashboard stopped reporting over its I2C bus — a connection fault far more often than a dead sensor.

1. Power down and reseat the signal ribbon between that hashboard and the control board at both ends.
2. Inspect the ribbon for cracks, kinked conductors, or bent connector pins, and swap in a known-good cable to isolate cable from board.

If it survives a clean reseat and a good cable, the on-board sensor or its trace is damaged and the board needs bench repair.

Chip loss — “detect 0 chips”

Strings like ChipSetting_get_addr_LTC detect 0 chips mean the controller walked that chain’s address string and found nothing — the whole chain is dark, not one weak chip. The BM1489 chips sit in a series string, so one break early in it hides everything behind.

1. Reseat both the data/signal ribbon and the board’s power connections for the affected chain.
2. Confirm the hashboard is actually receiving its supply voltage — a chain with no power reports zero chips — then re-run the detect/self-test.

The L7 regulates voltage per power domain, not per chip (roughly five chips share one DC-DC converter), so one failed domain can drop a block of chips at once. If reseating doesn’t restore the count, the board needs component-level diagnosis.

Data-storage (EEPROM) error — “eeprom_key_version or eeprom_encryption_algorithm error”

Each hashboard carries a small EEPROM holding its calibration, frequency table, and a signed version/key block. Bitmain encrypts this, so a failed read trips eeprom_key_version or eeprom_encryption_algorithm errors and the board is refused — usually from a marginal ribbon connection or a firmware/board mismatch.

1. Reseat the ribbon for the flagged chain first — a noisy read often traces back to the cable.
2. Re-flash the control board (“card flash”): write the official L7 firmware image from Bitmain’s support portal to a microSD card and boot from it. Use only the genuine image for your exact model — never a random third-party build.

If a clean reseat and a fresh flash don’t clear it, the EEPROM on the hashboard has failed and the board goes to repair.

Version error — “get_sw_version error”

A message such as chain_offset 1, chain 1, get_sw_version error means the controller couldn’t read the version block from that board’s storage — closely related to the EEPROM fault, and a communication or firmware-mismatch symptom rather than a dead chip.

1. Reseat the ribbon on the named chain.
2. Card-flash the control board with the correct official firmware so controller and boards agree on version. If it persists after both, the board goes to repair.

Pool connection error — “stratum connection timeout”

Messages like stratum connection timeout or poolno=2 msg="...retry after 30 seconds failures 1" are network-side, not hardware. The miner reached for its pool over Stratum and couldn’t open or hold the session. An intermittent uplink produces these even when every board is healthy.

1. Confirm the pool URL, port, and worker name are exactly right, and that the miner can reach the internet and resolve the pool’s hostname.
2. Add a backup pool so one outage doesn’t stall the machine.

The L7 idles its hashboards when it can’t reach a pool — it does not sit burning full power into dead work — so timeouts cost uptime, not a cooked board.

Internet error — “net lost … poweroff”

A fatal line such as error="net lost" msg="lost internet 1200 seconds > 20 minutes, poweroff." is the L7 protecting itself: after 20 minutes with no internet, the firmware deliberately powers the hashboards down rather than hash into nothing. Designed behavior, not a hardware fault.

1. Check the physical link — cable, switch port, and the miner’s IP/DHCP lease — and confirm the gateway and DNS are reachable.
2. Once connectivity returns the L7 resumes hashing on its own; if it doesn’t, reboot it.

Configuration error — wrong URL, port, or worker

The hint “Most likely you have input the wrong URL, forgotten to add a port, have not set up workers, or the network was disconnected” is a plain config mistake surfacing as a connection failure. Check each field:

• Pool URL in the exact stratum+tcp://host:port form your pool specifies — a missing port is the single most common cause.
• Worker/username in the pool’s required format (often account.worker), and the password set to whatever the pool expects (many accept x).

Field fix versus bench repair

Reseating cables and a clean card-flash clear most ribbon- and firmware-class faults. Dead sensors, failed EEPROMs, chains still dark after a good reseat, and chips lost to a blown domain are board-level work. Our ASIC fault finder maps symptoms to likely failed components.

Related: source replacement fans and temperature sensors from ASIC repair parts, book bench diagnosis through start a repair, and pull the correct wiring and reset procedures from the official miner manuals.