Inductor

An inductor is a passive two-terminal component, usually a coil of wire around a magnetic core, that stores energy in a magnetic field whenever current flows through it. It resists sudden changes in current, which makes it the energy-storage element at the heart of every switching power stage that feeds a mining ASIC — from the massive stages inside an APW12 to the small converters on a control board. Inductance is measured in henries (H), though the parts you will meet on mining hardware are typically in the microhenry (uH) range: squat, square, shielded packages that look like grey or black blocks with the winding hidden inside.

Role in switching converters

In a buck converter, the switching MOSFET rapidly chops the input voltage and the inductor averages those pulses into a smooth, lower-voltage output. During the switch's "on" phase the inductor stores energy in its magnetic field; during the "off" phase it releases that energy to keep current flowing into the load. Paired with a downstream capacitor, it filters the ripple that would otherwise reach the ASIC's sensitive core rails. The same component works in reverse in a boost stage: on many Antminer hashboards, a boost circuit steps the PSU rail up (for example 14V to 19V on S19-class boards) to feed the series-connected chain of voltage domains, and its inductor is the part doing the lifting. If that boost stage dies, every domain on the board reads zero volts and the board reports no chips at all.

Failure and saturation

Inductors rarely fail electrically on their own, but their magnetic core can saturate if current exceeds its design limit. When a core saturates, its inductance collapses, current spikes sharply, and the switching MOSFET beside it often fails as a consequence — so a blown power stage frequently points back to an over-stressed inductor rather than a spontaneously bad transistor. Physical damage is the other culprit: cracked ferrite from mechanical shock, scorched windings from a sustained overcurrent, or a pad that has lifted after years of thermal cycling. A visibly burnt or discolored inductor is one of the few power-stage faults you can sometimes catch with eyes alone before a meter ever touches the board.

Bench diagnosis

On the bench, an inductor should read as a near-short in a continuity test — a coil of copper has very low DC resistance. An open reading means broken windings or a cracked joint and condemns the part immediately. The more common workflow on a dead hashboard is indirect: measure the boost output where the schematic expects roughly 19–25V, and if it is absent, inspect the boost IC, MOSFET, diode, and inductor as a group, because a fault in any one of them takes the whole stage down. Each hash domain also has its own test point, so once the boost rail is confirmed you walk domain to domain and find where the voltage chain breaks. A bench power supply with current limiting is your friend here — it lets you power a suspect stage without letting a saturating inductor take out a fresh MOSFET.

Two habits speed up inductor work considerably. First, compare against a known-good board of the same model whenever possible — identical stages should show identical parts, identical DC resistance, and identical voltages, so any asymmetry points straight at the fault. Second, treat a hot inductor as a symptom, not a diagnosis: an inductor running noticeably hotter than its siblings is usually passing excess current into a downstream short rather than failing itself, so find what it is feeding before condemning the coil.

For the sovereign repair mindset, the inductor is a reminder that a "dead" board is usually a five-dollar component, not scrap. Learn to trace the power path — PSU, boost stage, domain chain — and most no-hashrate boards become diagnosable in minutes. If you would rather hand the board to someone who does this daily, D-Central's repair service works these exact failure trees on the bench every week.