Whatsminer M30S – Internal PSU Board Failure

Kill the PDU breaker first — never hot-disconnect a live Whatsminer PSU. The integrated P221/P222 is not hot-swappable; interrupting AC while DC is loaded kills the PSU controller and can brick the control board. Wait 10 minutes before opening the chassis so the PFC and output caps drain.

Pull the current hex code. Open WhatsminerTool V9.0.1, select the miner, Remote Ctrl → ExportLog, and grep `power.log` for lines like `psu_status: 0x0040`. If the UI shows only a decimal error (236, 268, 329 etc.), the hex code is still in the log — that's the real diagnostic, not the decimal MicroBT surfaces.

Measure AC at the miner inlet under full load. Target ≥205 V for North American 220 V single-phase, ≥235 V for 240 V split-phase, ≥202 V for 208 V commercial. A logging multimeter on the inlet for 24 hours will catch the evening-sag pattern that drives a permanent `0x0001` or code 206/250/251.

Confirm your circuit. M30S at stock pulls ~15.5 A on 220 V. NEMA 6-20 (20 A) is the absolute minimum; 6-30 is safer once you've added any derate. If a 15 A circuit is trying to feed it, every sag will throw an input-side PSU hex bit regardless of PSU health.

Cold-boot the PSU. Disconnect AC for 10+ minutes so the caps drain fully, then re-power. Code 267 (watchdog protection) and `0x2000` (firmware-lock) clear on a cold boot roughly 60% of the time in D-Central's repair queue — faster than the `contact technician` path MicroBT publishes.

Re-seat the I2C communication cable between the PSU and control board. Pin oxidation on this 4-pin connector is the single most common cause of code 263/264 and intermittent `0x0400` flags. A drop of DeoxIT D5 on the pins, full mate, listen for the click.

Torque the copper busbar screws to 2.0-2.5 Nm (18-22 in-lb). MicroBT publishes no spec; loose busbars arc under load, throw codes 233-235 and drive repeat 236-238 / 268 events. A cheap torque screwdriver pays for itself the first time it prevents a hashboard recap.

Swap the PSU internal fan before the PSU. Hex `0x0100` and codes 253/254/274 are fan-related. The stock 120 mm sleeve-bearing fan is a $15 generic part; replacing it costs 20 minutes and saves a $300-$450 PSU swap. If the PSU runs cool after the fan swap and the code stays clear, you're done.

Clean the PSU intake and the chassis intake. Dust on the PSU intake raises internal temp, triggers `0x0080` / code 275 (over-temp warning), and accelerates cap failure. Blow out with compressed air at the breaker-off state — never with the PSU live.

Isolate hashboards on output-side faults. Using WhatsminerTool, disable hashboards one at a time (Remote Ctrl → disable SM0/SM1/SM2) and re-test. If code 236/238/268 or hex `0x0040` clears with one board removed, that board has a chip-level short — the PSU is innocent (community field data says this is the 95% case MicroBT misdirects).

Measure hashboard rail voltage at the busbar under full load. Healthy M30S: 14.2-14.8 V. Below 14.0 V sustained means PSU output caps are tired or the feedback loop is drifting — swap PSU or ship to bench. Above 14.9 V means over-voltage protection is about to trigger on a hashboard and you risk chip damage if you keep running.

Swap in a known-good P221/P222 PSU. Mechanical fit is not electrical fit — P221B/C are M30S-compatible; M30S++ often needs P222. If the same hex code appears on a known-good PSU, the fault is upstream (control board, I2C, adapter plate) or the hashboards are drawing a fault current. Return to step 10.

Check for code 8700 (PSU/miner model mismatch). A P222 on an M30S config file throws this; so does swapping in a salvaged PSU from a different production batch. The control board reads PSU model ID over I2C at boot — mismatched ID is a hard stop even with a physically identical connector.

Update firmware only from a known-good network. Codes 800/801/802 (checksum errors) and `0x2000` can be triggered by interrupted firmware flashes. Use WhatsminerTool's firmware upgrade with a wired connection to the miner — never flash over WiFi or a flaky LAN. Power-cycle via the PDU after flash completes.

Bench-level PFC cap recap (Tier 3). If `0x0200` persists after fan and I2C fixes, the primary-side PFC capacitors are drying out. Typical failure: Nichicon PW or Rubycon ZLH 470μF 450V electrolytics — replace with 105°C-rated equivalents, dress the leads, and recap both bulk caps in pairs. This is a hot-air + soldering iron job with mains-level voltage risk.

Bench-level output-stage diagnosis (Tier 3/4). Output under-voltage (`0x0008`) that survives a fan and cap swap points to the feedback optocoupler or the DC-DC controller IC. This is not a garage job — the PSU is still storing hundreds of volts even after AC is removed. Ship to D-Central.

Check for control-board masquerade. Code 329 (control-board temp sensor comm error) and persistent `0x0400` often look like PSU faults but are the control board. Swap in a known-good control board; if the fault disappears, the PSU was innocent. MicroBT docs misdirect this — community data is unanimous.

Rule out the adapter plate. The small PCB between the PSU and hashboards (the "button board" / adapter plate) carries both power and sensor signals. Cracks, solder fractures, or bent pins here masquerade as PSU output faults. Visually inspect, reflow any suspect joints, and re-seat every connector. Zeus Mining and BiXBiT both flag this as an under-diagnosed failure mode.

Cold-climate sanity check. If your M30S intake is below 0°C (Canadian garage in January), warm the miner to room temp before energizing. Electrolytic caps in the PSU lose ESR margin at cold temps and can trigger spurious `0x0080` / `0x0200` on cold start. MicroBT documents nothing below 0°C; we do. Let it soak warm for 30 minutes.

Stop DIY and ship to D-Central when: (a) hex `0x0008` / `0x0010` / `0x0800` / `0x1000` / `0x2000` survives a cold boot, (b) you see bulged caps, discoloration or smell burnt electrolyte, (c) output voltage stays below 13.8 V under load with a known-good control board, (d) a known-good PSU reproduces the same hex code — PCB-level fault, or (e) any mains-side repair you're not already comfortable with. Book the repair, pack the miner with the PSU bolted in, include the hex codes and decimal codes observed, and tell us your circuit voltage and breaker size on the packing slip.