1 PC Used Fanuc A20B-2101-0040 PCB Board In Good Condition A20B21010040 A2OB-21O1-OO4O

FANUC A20B-2101-0040 | Alpha i SVM1 Drive PCB — A06B-6117 Series / 6-Port / Ribbon Side-Mount Connection

Drive-Side Intelligence for the A06B-6117 Servo Amplifier

The A20B-2101-0040 is the drive PCB inside FANUC's A06B-6117 series Alpha i SVM servo amplifier — a single-axis module used in FANUC CNC machine tool systems. Inside any Alpha i SVM, the hardware splits between two main boards: a control card that processes servo commands from the CNC and closes the control loop, and the drive board — the A20B-2101-0040 — that converts those control signals into the transistor gate drives that switch motor current.

The drive board sits closest to the power stage. It generates the PWM gate signals that activate the IGBT output transistors at precisely the right moments to produce the commanded motor current waveform. It also handles the real-time current feedback measurement that the servo loop needs to regulate motor torque. If this board fails, the gate signals become incorrect or disappear entirely — the motor current becomes uncontrolled, producing overcurrent trips, phase alarms, or complete output failure.

The 6-port, ribbon-style side-mounted connection is a physical characteristic of this drive board generation. Six signal interface points sit along the board edge in a ribbon format, accessible from the amplifier's side during maintenance. The side-mounted arrangement allows the board to be partially serviced within the amplifier housing without full module disassembly.

Key Specifications

Distinguishing Drive Board Faults from Control Card Faults

Power-stage alarm codes on the FANUC servo amplifier — overcurrent (alarm 6), DC link voltage (alarm 5 or 9), IPM fault, or phase-loss alarms — during motor operation point to the drive board. These are current-path alarms: the board is in the direct path of the motor phase current.

FSSB communication alarms, servo initialisation failures, or alarms appearing before motion is commanded indicate control card or communication path faults rather than the drive board. Correct alarm code interpretation before ordering replacement boards eliminates unnecessary costs from replacing functioning hardware.

FAQ

Q1: Does the A20B-2101-0040 work in A06B-6114 or other Alpha i SVM variants?

No. The A20B-2101-0040 is specifically matched to the A06B-6117 series interface architecture, signal levels, and physical connector layout. A06B-6114 uses a different drive PCB series (A20B-2100-xxxx range), and A06B-6096 uses earlier variants still. Fitting a drive board from the wrong amplifier generation produces mismatched gate drive timing, connector incompatibility, or protection circuit conflicts. Confirm the amplifier's own label before specifying a replacement.

Q2: Can the A20B-2101-0040 be tested as a standalone board?

Standalone bench testing of this drive PCB is not conclusive — functional gate drive verification requires the complete amplifier module operating under motor load, where the full DC bus voltage, current feedback, and thermal conditions are present. Swap testing with a confirmed-good A20B-2101-0040 in the complete amplifier module is the valid verification approach.

Q3: The SVM alarm appears only when the axis is under load. Does this suggest a drive board fault?

Load-dependent faults — overcurrent or thermal alarms that appear only under motor load but clear at idle — are consistent with a borderline failure in the drive board's current-switching path. A transistor or gate driver with marginal performance may handle low-speed idle conditions but fail at the current levels commanded under load. A drive board swap under supervised test conditions (incrementally increasing load) is the appropriate diagnostic.

Q4: How is the A20B-2101-0040 identified from a pool of similar Alpha i drive boards?

Read the part number label on the board directly — the full A20B-2101-0040 designation is printed on the board. Do not attempt to identify Alpha i drive boards by visual comparison alone. Adjacent variants (A20B-2101-0041 through -0045) may appear identical physically while serving different SVM configurations. The board label is the only reliable identification source.

Q5: Is repair viable for the A20B-2101-0040, or is replacement the only option?

Repair is available through FANUC Alpha i drive PCB specialists. Common repairable failures include gate driver IC failure, IGBT-side protection components, and current sensing circuit damage. Repair centres with A06B-6117 test fixtures can verify the repaired board at full rated current before return. For a board that has sustained severe overcurrent damage (visibly burned components), replacement is more economical than repair.