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Key Technical Specifications
| Parameter | Value |
|---|---|
| Part Number | A20B-2101-0050 (200–240 V); A20B-2101-0051 (400–480 V HV) |
| Board Type | Control PCB for βi Series Servo Amplifier (SVM) |
| Compatible Amplifiers | A06B-6130-H002 (SVM-4i/20i, 200–240 V); A06B-6131-H002 (SVM1-20HVi, 400–480 V) |
| Input Voltage (Main Power) | 200–240 VAC (+10%, −15%), 50/60 Hz (A20B-2101-0050) or 400–480 VAC (+10%, −15%) (A20B-2101-0051) |
| Control Power Supply | 24 VDC (+10%, −10%), 0.9 Arms |
| Interface | FSSB (FANUC Serial Servo Bus) |
| Control Method | Sine Wave PWM with Transistor Bridges |
| Rated Output Current | Depends on amplifier unit (e.g., 8.0 Arms for SVM-20i; 5.6 Arms for SVM1-20HVi) |
| Power Supply Rating | 0.2–2.8 kVA (200 V class); 2.5 kVA (400 V class) |
| Cooling | Internal fan (amplifier-level); board operates within amplifier enclosure |
| Dimensions (approx.) | ~160 mm × 100 mm (varies by revision and suffix) |
| Weight | ~0.15–0.25 kg (board only) |
| Mounting | Internal PCB slot in βiSV servo amplifier chassis |
| Revision Suffixes | /09F, /12G, etc. (indicate hardware/firmware revision) |
| Typical Use | Axis control logic, FSSB communication, PWM generation, protection functions |
Product Introduction
The FANUC A20B-2101-0050 and A20B-2101-0051 are control PCBs used inside FANUC βi Series servo amplifier units (βiSV, SVM). The A20B-2101-0050 is used in 200–240 VAC input amplifiers such as the A06B-6130-H002 (SVM-4i/20i), while the A20B-2101-0051 is used in 400–480 VAC high-voltage input units like the A06B-6131-H002 (SVM1-20HVi).
These boards handle axis control logic, FSSB communication with the CNC, PWM signal generation for the transistor bridges, and protective functions (overcurrent, overheat, DC link monitoring). They are critical for reliable servo operation in CNC machines and are often replaced when amplifier control faults occur.
A20B-2101-0050
A20B-2101-0050
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Amplifier shows SV0401/SV0430 alarm (control error) | Control PCB fault or firmware corruption | ✅ High | Check amplifier alarm codes on CNC diagnostic screen; verify FSSB communication status | Usually requires control PCB replacement or amplifier-level repair |
| No display, no fans, dead amplifier | Main power or control power supply failure | ❌ Low | Measure 200–240 VAC (or 400–480 VAC) at amplifier input terminals; check 24 VDC control supply | Check external power, fuses, and contactor before replacing PCB |
| Intermittent axis faults, random alarms | Loose PCB connector, FSSB cable issue, or noise | ⚠️ Medium | Reseat FSSB and control connectors; inspect FSSB cable shielding and routing | Clean contacts, reseat firmly; replace FSSB cable if damaged |
| Overcurrent alarm on startup | Transistor module failure or shorted motor phases | ⚠️ Medium | Measure motor phase-to-phase resistance; check for shorts to ground | Issue is likely at power stage or motor, not control PCB itself |
| Amplifier works on one axis but not another | Axis-specific configuration or parameter mismatch | ⚠️ Medium | Compare servo parameters for affected axis; check motor code and FSSB address | Verify parameters and motor selection; PCB likely OK |
| Board fails after swap | Wrong voltage class (0050 vs 0051) or revision mismatch | ✅ High | Compare old board label (A20B-2101-0050 vs 0051, suffix) before removal | Match exact part number and voltage class on replacement |
If you’re stuck, send photos of the amplifier model, board label, and any CNC/servo alarm screens. We’ll review them before you commit to a swap.
Frequently Asked Questions (FAQ)
Q: What’s the difference between A20B-2101-0050 and A20B-2101-0051?
A: The is the control PCB for 200–240 VAC input βiSV amplifiers (e.g., A06B-6130-H002 SVM-4i/20i). The A20B-2101-0051 is for 400–480 VAC high-voltage input units (e.g., A06B-6131-H002 SVM1-20HVi). They are not interchangeable—using the wrong voltage class can destroy the board and amplifier.
Q: Can I buy just this PCB, or do I need the whole amplifier?
A: FANUC does not officially sell these PCBs as standalone spare parts; they are considered internal components. However, independent suppliers and repair shops stock and test them separately. For critical machines, many plants keep a spare amplifier rather than just a board.
Q: Will my servo parameters survive a control PCB swap?
A: No. Servo parameters are stored in the CNC memory, but some amplifier-specific data (e.g., motor code, FSSB configuration) may need to be re-verified after a board swap. Always back up your servo parameters and FSSB configuration before hardware changes.
Q: Is this board compatible with αi or βiS amplifiers?
A: No. The /0051 are specific to βiSV (SVM) amplifiers. αi and βiS series use different control boards and architectures. Always match the board to the exact amplifier model.
Q: Why is this cheaper than buying a new amplifier from FANUC?
A: This is new surplus or inspected stock from decommissioned systems and authorized distributors. It’s genuine FANUC hardware, function-tested, but sold as a component rather than a complete new amplifier. That’s why the price is lower while still carrying a 1-year replacement warranty.
Q: What condition is the unit in—new, used, or refurbished?
A: We list each unit explicitly: “New Original / New Surplus” means factory-sealed or unused surplus with original packaging; “Refurbished (tested)” means cleaned, electrically tested, and verified functional in a βiSV amplifier test rig. The product page or quote will state which applies.
Q: Do you provide test reports or in-circuit test data?
A: Yes. For refurbished units, we can supply a basic functional test report (power-up, FSSB handshake, PWM output verification, alarm simulation) and short test video on request. Just ask before purchase.
