Power Supply Unit A20B-1000-0770 A2OB-1OOO-O77O A20B10000770

FANUC A20B-1000-0770 | PSU1 / PSU2 Power Supply PCB — F12/F120/F15/F150 CNC + R-H Robot / E1 / G1 

Power Supply for Two Generations — CNC and Robot

The A20B-1000-0770 is the PSU (Power Supply Unit) PCB for FANUC's F12/F120 and F15/F150 series CNC controls and the R-H robot controller. It occupies the PSU1 or PSU2 position within the controller's power supply rack, converting the AC input and internal bus voltages to the regulated DC supplies that the control's circuit boards require for operation.

The power supply designation #12/120 / 15/150 covers two distinct CNC control generations: the F12 and F120 series (compact, high-performance CNC controls for machining and turning) and the F15 and F150 series (multi-axis, high-capability CNC for complex machining). The same A20B-1000-0770 PCB serves PSU positions in both controller families. The E1 and G1 designations within the power output configuration identify specific voltage output variants of this board, matched to the particular controller rack position.

The R-H robot controller application makes this one of the few power supply boards in FANUC's A20B-1000 series that serves both CNC machine tool controls and robot controllers. The power architecture of these FANUC controllers is sufficiently common that a single PSU board design serves multiple platforms — a design approach that simplified FANUC's parts inventory and extended the board's applicability across product lines.

Key Specifications

Failure Symptoms and Fault Isolation

A failed A20B-1000-0770 typically manifests as the controller failing to power on, or the CNC/robot losing specific regulated voltages that cause one functional area to fail while others continue. The power supply PCB outputs multiple voltage rails — a failure of one rail while others remain within specification can produce partial system failures that appear as intermittent faults rather than complete power loss.

When the controller shows a power supply alarm or fails to complete its startup sequence, measure the DC output voltages at the power supply's test points (referenced in the controller's electrical maintenance documentation) before concluding the PSU PCB has failed. Confirm that the AC input voltage at the supply's input is within specification and that the downstream load does not have a short circuit consuming excessive current.

FAQ

Q1: What FANUC controllers does the A20B-1000-0770 power supply serve?

The A20B-1000-0770 serves as PSU1 or PSU2 in FANUC F12/F120 series CNC controls, F15/F150 series CNC controls, and the FANUC R-H robot controller. The specific PSU position (PSU1 or PSU2) and the E1/G1 output configuration determine which position in a specific controller this board fills.

Q2: What is the difference between PSU1 and PSU2 positions?

In FANUC controllers using a dual-PSU architecture, PSU1 and PSU2 supply different sets of regulated DC outputs to different sections of the controller's circuitry — for example, logic power for the CPU boards versus power for the I/O interface boards. The A20B-1000-0770 can serve either position; the specific voltage rails it provides are configured by hardware jumpers or the E1/G1 output variant. Confirm the position and variant from the controller's power supply slot documentation.

Q3: The controller powers on but one functional area (e.g., all axes or all I/O) does not respond. Could the PSU be the fault?

Yes. If the PSU PCB fails to supply one voltage rail while others remain active, the functional area powered by that rail loses power while the rest of the controller operates normally. This produces partial failures that resemble board faults or software issues. Measure the DC output voltages from the PSU at the points defined in the controller's electrical specification — a voltage out of tolerance or absent confirms the power supply as the fault.

Q4: Can the A20B-1000-0770 be repaired?

Yes — repair is widely available and is the standard approach for this discontinued unit. Common failure points include electrolytic capacitors (failure through ESR increase or electrolyte leakage), rectifier components, and PWM controller ICs. Specialist FANUC power supply repair services carry load test fixtures for F12/F15 and R-H controller configurations to verify the repaired board under realistic current load conditions before return.

Q5: Where is the A20B-1000-0770 sourced after discontinuation?

Through the FANUC F12/F15 and R-H robot power supply aftermarket — FANUC PSU repair specialists, tested surplus suppliers, and exchange services holding A20B-1000-0770 stock. Confirm the specific revision (-01, -08A, or base) from the installed board's label before ordering. Repair is the most economical and logistically practical path for this discontinued board — exchange and repair services are widely available for this unit.