Bitaxe – ESP32 Brownout Detector Triggered (Reset Loop)

Move the Bitaxe directly onto a wall outlet on its own circuit. Unplug it from every USB hub, surge strip, extension cord, and shared adapter. Do not share the circuit with a fridge compressor, microwave, HVAC blower, or washing machine. Shared-rail brownouts are the single most common Bitaxe brownout cause in D-Central's support queue — before anything else, fix the power topology and observe 10 minutes.

Swap the PSU for a known-good, oversized adapter name-branded by a credible manufacturer. Size at 1.5x expected steady-state draw: Ultra / Supra 5V 4A minimum, Gamma 5V 6A minimum, GT 60W+ USB-PD brick with a quality PD-to-barrel trigger cable or 5V 10A+ barrel supply, Hex per the v303/v304 12V spec. Don't reuse the original adapter to 'test'; PSU specs on cheap labels are aspirational. If brownouts clear, replace the old adapter permanently; don't trust it for another miner.

Swap the barrel-jack (or PD trigger) cable for a short, thick-gauge one: <=1 m, 20 AWG or better. Thin 26 AWG 2-3 m cables drop 0.3-0.5 V at full Bitaxe load — enough to turn a 5.05 V adapter into a 4.60 V brownout trigger at the board. If the adapter measures clean at its own terminals but VIN at the jack reads low under load, the cable is the fault. Cheap Amazon-basics cables with marked gauge are fine; the phone-case-brand LED cables are not. Test cables on a phone in File Transfer / MTP mode before trusting them.

Inspect connectors under good light or a loupe. Check: barrel-jack center pin (not spread or wobbly), barrel-jack solder (no hairline cracks around the footprint), XT30 on GT (pins seated, no walk-out, no discoloration), USB-C shell (no bent shell, no dust). Clean the contact surfaces with 99% isopropyl alcohol and a lint-free wipe; let it dry 60 seconds before re-mating. Connector resistance under the high transient current of ASIC init drops enough voltage to trip the BOD exactly like an undersized PSU does.

Confirm the reset reason on serial. Plug USB-C from Bitaxe to laptop. Open a serial monitor at 115200 8N1: `idf.py monitor`, `pio device monitor`, Arduino Serial Monitor, `screen /dev/ttyUSB0 115200`, or PuTTY on Windows. Power the Bitaxe from its barrel jack, not from laptop USB — you want real rail behaviour under ASIC load. Capture three full boot cycles. You should see `Brownout detector was triggered` and / or `rst:0xf (RTCWDT_BROWN_OUT_RESET)`. Different reset reason? You're on the wrong page — see Related Errors.

Measure VIN at the barrel-jack solder pads under load. Multimeter on DC volts. Probe while the miner is attempting to boot and the ASIC is trying to ramp — not at idle before power-on. Target sustained: >= 4.9 V on 5V-family Bitaxes (Ultra/Supra/Gamma/GT), >= 11.5 V on Hex. Never below 4.7 V or 11.0 V respectively on transient. If VIN sags below those thresholds despite a known-good PSU and cable, something downstream is pulling too hard — suspect TPS546 fault (Gamma / GT) or a shorted output-side cap.

Measure the 3V3 rail at any accessible ESP32-side test point (many Bitaxe boards have a labelled 3V3 pad). Target: 3.27-3.33 V sustained under load. A clean VIN (>=4.9V) combined with a collapsing or oscillating 3V3 means the 3V3 buck on the ESP32 side has failed; that's a bench-level rework. If 3V3 reads clean but the BOD still trips, the transient is below your multimeter's bandwidth — move to Step 8 and scope the rails.

Run a DC electronic-load test on the suspect PSU at 1.5x Bitaxe nominal. A 5V 6A Gamma PSU should hold >= 4.95 V at 4 A. A 5V 4A Ultra / Supra PSU should hold >= 4.95 V at 3 A. Any adapter that droops more than 2% of nameplate under rated load is too soft for continuous mining. This is the step that catches aged PSUs that pass a multimeter check at idle but fail under actual draw — silent killer on long-running Bitaxe fleets.

Scope the rails for sub-multimeter transients. Two-channel oscilloscope: probe VIN DC-coupled and 3V3 DC-coupled, 10x probes, 20 MHz bandwidth minimum. Trigger on negative slope crossing 4.7 V (VIN) or 3.0 V (3V3). During the ASIC init transient look for spikes down, not up. If you see VIN momentarily crashing to 4.5 V for tens of microseconds but averaging 4.95 V, you've found a transient sag that a multimeter can't catch. Fix path: add bulk capacitance at VIN (bench workaround) or size the PSU larger; confirm whether the transient source is upstream (supply) or downstream (TPS546 inrush).

If VIN transient sag is real and sourced downstream, confirm TPS546 health. Probe VOUT on the TPS546 during a boot attempt. Gamma core rail is nominally 1.1-1.3 V (firmware-configurable via AxeOS). Oscillation, sustained drop below spec, or collapse to 0 V with a valid VIN indicates TPS546 input filtering failure or the IC itself. If the TPS546 is failing and dragging VIN into brownout as a cascade, treat the TPS546 as the primary fault — see the bitaxe-gamma-tps546-vcore-init-failed page. SOIC-10 package on most Gamma revs; hot-air rework, not a soldering-iron job.

Add a UPS or line-interactive regulator if brownouts cluster at a specific time of day. Residential line voltage sag during 5-10 PM neighbourhood peak load is a published problem; if your wall voltage drops below 115 V (120 V nominal) or below 225 V (240 V split-phase) when the brownouts hit, no amount of PSU upgrading will fix the miner side. A 600 VA line-interactive UPS holds output regulation within a few percent through typical residential sag events and also protects against OTA-during-outage bricks. Log your wall voltage with a plug-in voltage recorder for 24 hours to confirm before buying a UPS.

Re-solder the barrel-jack footprint if physical stress has cracked solder under the connector. Symptoms: cable wiggle causes brownouts, VIN reads clean when probed directly at the PSU end but drops when probed at the jack. Remove old solder with wick, clean with IPA, apply fresh flux, re-solder all four mechanical tabs plus the two power terminals with a 60/40 or lead-free solder. This is a soldering-iron job (T12 tip at 360 C), not hot-air. Reseat the cable with a test pull before powering the miner.

Replace the barrel-jack connector outright if the center pin is spread, corroded, or mechanically damaged. Desolder the old connector with hot air (300 C, 30 s) and tweezers. Clean footprint with wick and IPA. Install a fresh 5.5x2.1 mm or 5.5x2.5 mm connector (match the original — check the board BOM or compare physically) and re-solder all tabs plus power terminals. Verify with a continuity test and a pull test before powering. A 5-dollar part fixes a chronic brownout source on well-used Bitaxes.

On GT, replace the XT30 connector if pins are walking out, discoloured, or loose. XT30 failures under vibration are a documented weak point on GT. Desolder the old connector with hot air; the XT30 is a two-pin through-hole part with heavy copper. Use a quality replacement XT30 (genuine Amass or equivalent) and re-solder with lead-free at 370 C. Verify polarity before powering — reversed XT30 instantly blows the TPS546 and the ASIC. A proper XT30 replacement eliminates chronic GT brownouts traced to connector contact.

Stop DIY and ship to D-Central ASIC + Bitaxe Repair when: three known-good PSUs all fail on three different outlets; VIN reads below 4.7 V under load with a 5V 6A supply and a short thick cable; scope shows clean rails but the BOD still trips; serial shows both brownout and TPS546 Power Fault in the same boot; visible damage on the buck converter, caps, or barrel-jack footprint; temperature-dependent brownout (works cold, browns warm) with no hot-air gear; or you don't own the bench tools to continue. Book a slot at https://d-central.tech/services/asic-repair/. We stock TPS546 bucks, barrel-jack and XT30 connectors, ESP32-S3-WROOM modules, and every Bitaxe ASIC variant. 3-7 business-day turnaround. Canada / US / international shipping. D-Central pioneered the Bitaxe ecosystem — Mesh Stand, first heatsinks for Bitaxe and Bitaxe Hex, full variant inventory.