The APW9 is Bitmain’s single-unit, high-current PSU built to feed the Antminer S17 and S17 Pro (the APW9+ is the same job for the S17+/S17e/T17+/T17e). Detaching it is a five-minute mechanical job, but the order of operations matters: you kill AC first, let the internal capacitors bleed down, then release the DC and signal connectors by the connector body, never by the wires. Do it in the wrong order and you risk a live-arc across a 170 A output or a lethal charge still sitting on the primary-side caps. Here is the exact procedure.
Before you start: what you’re working with
The APW9 delivers an adjustable 14.5–21 V DC rail at up to 170 A (3600 W @ 220 V) to the three hash boards, plus a low-current feed and an I2C signal line to the control board. It is rated for 200–240 V input, where it delivers its full ~3600 W output; it will still run on a 110/120 V circuit, but at reduced output — and a single 15 A/120 V branch circuit cannot supply an S17’s full draw. Two things make it dangerous even when unplugged:
- Stored charge. The primary-side PFC capacitors hold roughly 400+ V DC after the AC is cut. They bleed down through internal resistors, but that takes time. Never open the PSU housing — the case is not a user-serviceable boundary, and there is no reason to open it just to detach it from a miner.
- High current on the output. The 14.5–21 V rail is low voltage but enormous current. A dropped tool or a half-seated connector across those bus pins will vaporize metal. Treat the DC side with the same respect as the AC side.
Tools you’ll need
- A #2 Phillips screwdriver (for any cable-retention screws / the PSU mounting screws)
- An anti-static wrist strap grounded to the chassis
- A flashlight or headlamp to see the connector latches
- Masking tape and a marker to label board-to-cable positions (Chain0/1/2)
- A multimeter (optional, to confirm the output has bled to 0 V before handling)
Step-by-step: detaching the APW9
- Stop the miner cleanly. If it’s still hashing, shut it down from the web UI (or your firmware’s stop command) so the ASICs and PSU aren’t under load at the moment you cut power.
- Cut and unplug the AC. Switch off the PDU/breaker feeding the unit, then physically pull the C19/C20 AC cord from the APW9 inlet. Confirm the miner is fully dark — no fans, no PSU LED. Do not rely on the switch alone; unplug it.
- Wait for capacitor bleed-down. Give it at least 3–5 minutes before touching any connector. This lets the primary-side caps discharge. If you have a meter and can safely reach the DC output terminals, verify they read ~0 V before proceeding.
- Ground yourself. Clip your anti-static strap to bare chassis metal. The BM1397 chips and the control board are ESD-sensitive; a static discharge during handling can latch a hash board into a fault.
- Label everything. Before you unplug a single cable, tape-label which DC output cable goes to which hash board (Chain0, Chain1, Chain2) and which port on the APW9 it came from. Re-mating boards to different rails or ports on reassembly is a common cause of “one chain dead” after a swap.
- Disconnect the signal / control cable first. The small multi-pin cable carrying the PSU enable and I2C sense lines to the control board is the low-energy connection — remove it first so the PSU is fully “told” to stay off. Squeeze the retention latch and pull straight off the header; don’t rock it side to side.
- Release the DC power cables from the hash boards. Each of the three hash boards receives a heavy-gauge DC cable from the APW9. Depress the connector’s locking tab (or back out its retention screw), then pull the connector body straight back — never yank the wire bundle. Pulling on wires can back a crimped pin out of the housing and leave you with an intermittent high-resistance joint that overheats later.
- Disconnect any remaining low-current / fan feed. Remove the auxiliary feed to the control board and any fan power that routes through the PSU harness, again by the connector body.
- Free the PSU mechanically. Remove the mounting screws or release the retention clips holding the APW9 to the miner frame, then lift it clear. Set it on an insulated, non-conductive surface — not on top of the hash boards or on bare metal.
For a visual walk-through of the same sequence, see the reference clip: Detaching the APW9 from an S17/S17 Pro.
How to confirm it’s done right
- The APW9 lifts away with no cable still tethering it to the frame, boards, or control board.
- Every connector housing is intact — no pins backed out, no exposed crimps, no bent blades on the hash-board power inputs.
- The AC cord is out of the PSU and stays out until you deliberately reconnect it.
- If you’re bench-testing the freed PSU, remember it needs its enable/signal line pulled correctly to output — a bare APW9 with only AC applied will normally sit idle by design, not spin up.
Common mistakes to avoid
- Pulling connectors by the wires. The single most frequent cause of a post-repair dead chain. Always grip the housing.
- Skipping the bleed-down wait. “It’s unplugged, it’s safe” is wrong — the primary caps stay charged for minutes. Be patient.
- Opening the PSU case. There is no field-serviceable part inside for a detach job, and the internal 400+ V bus is lethal. If the APW9 itself is faulty, replace it — don’t crack it open.
- Mixing up APW9 and APW9+. They share the 14.5–21 V / 3600 W envelope but the APW9+ is a 200 A unit for the S17+/e and T17+/e. Match the PSU to the miner generation on reassembly.
- Expecting full output on a 120 V circuit. The APW9 is rated for 200–240 V, where it makes its full ~3600 W. It will still power up on 110/120 V, but at reduced output — a single North-American 120 V branch circuit can’t feed an S17 at full draw, so plan for a 200–240 V supply if you want rated performance.
When to escalate
If you find scorched connector housings, melted pins on a hash-board power input, or a PSU that smells burnt or shows bulged casing, stop and treat it as a fault diagnosis rather than a routine detach. Scorched high-current connectors point to a resistive joint that was cooking under load, and the mating hash board should be inspected before it goes back into service. If you’re not confident isolating a live 200–240 V circuit, hand the job to a qualified tech.
Related
Reattaching or swapping the unit? Work through the per-model repair manuals and grab replacements from ASIC repair parts. If the miner threw a fault before you pulled the PSU, look the code up in the ASIC fault finder, and when you’d rather have it handled on the bench, start a repair with us.
