Bitaxe – PSU Undersized / Insufficient Wattage for Overclock

Read the PSU nameplate. If it's below the variant minimum, swap it. Supra / Ultra want >= 5V 3A (sane buy 5V 4-5A). Gamma wants >= 5V 4A (sane buy 5V 6A). Hex wants >= 12V 2.5A (sane buy 12V 3-5A). Bitaxe GT wants 5V 8A or 65W USB-PD. This single move clears the majority of BITAXE_PSU_UNDERSIZE tickets. Don't troubleshoot upstream of arithmetic — the answer is on the brick. D-Central stocks Bitaxe-rated supplies sized correctly per variant; don't grab the closest spare.

Move the Bitaxe to its own wall outlet, no hub, no shared adapter. Direct into the wall, on a circuit not shared with a fridge compressor, microwave, HVAC blower, washing machine, or kettle. Multi-port USB chargers and smart strips brownout-correlate clusters — one ramping unit can pull the others into reset. Free, takes 30 seconds, do this before changing anything else. Observe 10 minutes of boot stability via OLED or serial.

Swap to a short, thick-gauge input cable. Maximum 1 metre, minimum 20 AWG (lower AWG = thicker wire). Match the connector to your variant: 5.5x2.1 mm or 5.5x2.5 mm barrel for 5V boards (check the board sticker); XT30 with 18 AWG silicone-jacketed wire for Hex. Verify the cable's marked gauge — unmarked cables are usually 26 AWG and silently kill regulation under Bitaxe current. A 1.5 m 26 AWG cable drops 0.30V at 5A. Mark the working cable; throw out the unmarked thin ones.

Inspect the input connector with a loupe or magnifier. Center pin (5V variants) straight and not spread. XT30 housing (Hex) free of melting, cracked plastic, or loose pin retention. Solder around the connector footprint clean and unbroken (no hairline cracks). No discoloration, dust, or lint in the contact. Wipe contact surfaces with 99% IPA on a lint-free wipe; let dry 60 seconds before re-mating. Connector resistance under high transient ASIC current drops the same kind of voltage as an undersized supply.

Hard power-cycle for 30 seconds (not a soft restart). Pull the supply, wait 30 seconds, plug back in. Observe a full ramp on serial or OLED. Not a fix on its own — but it confirms the boot pattern after the PSU / cable / connector change you just made. If the loop persists, you haven't actually solved it; continue to Tier 2 with diagnostics.

Put an ammeter inline and read actual peak current under load. USB-A charge doctor for USB-A supplies. USB-C KM003C PD analyzer for USB-PD. Barrel-jack inline ammeter for barrel 5V supplies. Multimeter in series on the XT30 positive lead for Hex. Read peak current during ASIC ramp, not steady-state. If peak exceeds PSU nameplate, confirmed undersized — replace, end of diagnostic. If peak is within nameplate but rail still sags (Step 8), the PSU is delivering current at the cost of voltage regulation; replace anyway.

Confirm reset reason on serial console. USB-C from Bitaxe to laptop. Open 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 or XT30 (not from laptop USB — you want real ASIC load, not USB-bus-limited idle). Capture three full boot cycles. Verify `Brownout detector was triggered` and `rst:0xf (RTCWDT_BROWN_OUT_RESET)`. If you see `Guru Meditation Error` instead, you're on the wrong page — see bitaxe-esp32-crash-loop. Reset reason is the most diagnostically valuable single number on a Bitaxe boot loop.

Measure VIN at the input pads under load. Multimeter on DC volts. Probe at the board (barrel-jack solder pads or XT30 pads), not the cable end or PSU end. Power the miner. Read voltage during idle, during ASIC ramp, and during the brownout itself. Targets: 5V variants >= 4.9V sustained, never below 4.7V transient. Hex 12V >= 11.7V sustained, never below 11.0V transient. If VIN reads below threshold under load with a known-good correctly-sized PSU and a short thick cable, you're dealing with a downstream-pull problem — Tier 3 territory.

Measure 3V3 at any accessible ESP32-side test point (most Bitaxe boards have a labelled 3V3 pad). Target: 3.27-3.33V sustained under load. Clean VIN combined with collapsing or oscillating 3V3 means the 3V3 buck on the ESP32 side has failed — that's hot-air rework territory, not soldering-iron. If 3V3 is clean but BOD still trips, the transient is below multimeter bandwidth — go to Tier 3 with a scope.

Run a DC electronic-load test on the suspect PSU at 1.5x variant nominal. Atorch DL24 or equivalent. 5V 6A PSU should hold >= 4.95V at 4A continuous with ripple <= 50 mV. 12V 3A Hex PSU should hold >= 11.85V at 2A continuous with ripple <= 100 mV. Anything that droops > 2% nameplate or rings with > 100 mV ripple is too soft for mining regardless of label. This is the silent-killer test that catches aged supplies passing idle multimeter checks but failing under real ASIC load. If the supply fails, replace it — don't move it to another miner.

Verify wall-outlet voltage with a plug-in voltage logger for 24 hours (Kill-A-Watt, Amprobe LM-100, P3 Kill A Watt P4400). If wall voltage drops below 115V (120V nominal) during evening hours, your residential circuit is sagging during neighbourhood peak load and that drop is being faithfully passed through the PSU regulation onto Bitaxe VIN. Fix at the wall: dedicated circuit, line-interactive UPS, or relocate the rig. Common culprits: 5-10 PM neighbourhood peak, electric-heating mornings in winter, well pumps on rural circuits.

Tune AxeOS down to stock if the loop only started after pushing coreVoltage or frequency. Web UI -> Settings -> System. Set coreVoltage to default for your variant (typically 1.20V Gamma stock, 1.20V Supra/Ultra stock — check release notes for current defaults). Set frequency to default (typically 525 MHz Gamma, 485 MHz Supra/Ultra). Save and reboot. If it now boots cleanly on the marginal PSU, the supply was already at the edge — replace the PSU before pushing the tune back up. Order matters: PSU upgrade first, performance experiments second. Pushing tune on a marginal PSU cascade-damages the TPS546 over time.

Scope VIN and 3V3 for sub-multimeter transients. Two-channel oscilloscope, 10x probes, >= 20 MHz bandwidth. CH1 on VIN DC-coupled at the input pads. CH2 on 3V3 DC-coupled. Trigger on negative slope crossing 4.7V (or 11.0V for Hex) on CH1. Capture the ASIC ramp. Look for: (a) transient sag (VIN momentarily dropping for tens of microseconds while average reads OK), and (b) input ripple (VIN swinging +/- 200 mV at 50-200 kHz, indicating PSU ripple beyond TPS546 input filtering). Both kill regardless of nameplate. Replace the PSU with a low-ripple supply if ripple is the issue.

Add bulk capacitance at VIN as a bench workaround for transient sag (NOT a permanent fix). Solder a low-ESR 100-220 uF electrolytic plus a 10 uF MLCC across VIN to ground at the input pads. This absorbs ASIC-ramp transients that would otherwise sag the rail. Diagnostic confirmation tool, not a repair. If the cap clears the brownout, the supply path is at the edge — still upgrade the PSU. Don't ship a Bitaxe to a customer with extra caps soldered on; fix the actual supply.

Re-solder the input connector footprint if physical stress has cracked solder under the barrel jack or XT30. Symptoms: cable wiggle correlates with brownouts; VIN reads clean directly at PSU end but drops at the connector. Remove old solder with wick, clean with 99% IPA, apply fresh flux, re-solder all mechanical tabs plus the power terminals with 60/40 or lead-free. T12 tip at 360 C, soldering-iron job. Verify with continuity test and pull test before powering. Reseat the cable.

Replace the input connector outright if the center pin is spread, corroded, the XT30 housing is melted, or pin retention is loose. Hot air at 300 C for 30 seconds, tweezers, lift the connector. Clean footprint with wick and IPA. Install fresh part — 5.5x2.1 mm or 5.5x2.5 mm barrel jack for 5V boards (verify against board sticker), or fresh XT30 PCB-mount for Hex. Re-solder all tabs and power terminals. Verify polarity before powering — reversed barrel-jack on Gamma instantly damages the TPS546 and the BM1370. A 5-dollar part fixes a chronic supply-path source on well-used boards.

Stop DIY and ship to D-Central ASIC + Bitaxe Repair when: three correctly-sized known-good Bitaxe-rated PSUs on three different outlets all reproduce the loop; VIN reads below threshold under load on a correctly-sized supply with a short thick cable; scope shows clean rails but BOD still trips; serial shows both `Brownout detector was triggered` and `TPS546 Power Fault Detected` in the same cycle (cascade damage); visible damage on the buck converter, MLCCs, or input connector footprint; melted XT30 housing on Hex; or you don't own the bench gear to continue. Book at https://d-central.tech/services/asic-repair/. We stock TPS546 spares, ESP32-S3-WROOM modules, barrel-jack and XT30 connectors, and every Bitaxe board revision. 3-7 business-day turnaround. Canada / US / international. D-Central pioneered the Bitaxe ecosystem — Mesh Stand, first heatsinks for Bitaxe and Bitaxe Hex, every variant in stock with bench fixtures and matched spare modules.