A20B-3300-0391 Fanuc PCB Board A20B33000391 A2OB-33OO-O39I

A20B-3300-0391 | FANUC B-Generation 6-Axis FSSB Servo Controller Card — C5410A / i-Series CNC and Robot / Single-Channel Fibre-Optic Servo

6-Axis FSSB — One Channel, Six Drives

The A20B-3300-0391 manages 6 servo axes through a single FSSB fibre-optic channel — placing all 6 drive interfaces on one communication loop. Within each FSSB cycle, the C5410A ASIC sends position commands to all 6 drives in sequence and reads back encoder feedback from each.

Six axes is a natural fit for the most common machine tool and robot configurations:

Standard 6-axis robot bodies: FANUC industrial robots are almost universally configured with 6 revolute joints (J1–J6) — one joint per axis of the A20B-3300-0391. A single card provides the complete joint servo interface for the robot.

Machining centres with 6 controlled axes: Complex machining centres with X, Y, Z plus three rotary axes (or two rotary axes plus a pallet servo) use 6 axes total.

Turning centres with multiple turrets and spindle positioning: Z, X, C-axis (spindle orientation), Y-axis, second turret, and subspindle together span 6 axes.

Key Specifications

A20B-3300-039x — The C5410A Servo Card Family

The 039x range forms a servo card family defined by the C5410A ASIC, with multiple axis count options:

All three use the same C5410A core and single-channel FSSB — the difference is axis count. The 6-axis 0391 is not interchangeable with the 8-axis 0390 or the 2-axis 0393, even though all share the same FSSB and ASIC architecture.

Application Scenarios

6-joint robot servo card fault: A FANUC robot controller develops FSSB communication alarms on joint axes. The A20B-3300-0391 is identified as the fault. Replacement restores FSSB communication to all 6 joint drives.

16i-B 6-axis machining centre servo fault: A Series 16i-B machining centre with 6 controlled axes develops simultaneous FSSB alarms. The A20B-3300-0391 is replaced. All 6-axis FSSB communication is restored.

FAQ

Q1: What is the main difference between A20B-3300-0390 (8-axis) and A20B-3300-0391 (6-axis)?

Both use the C5410A ASIC and single-channel FSSB. The 0390 manages 8 axes; the 0391 manages 6 axes. For standard 6-joint robot bodies or 6-axis CNC configurations, 0391 is the correct card. For 8-axis configurations, 0390 is required. They are not interchangeable even though they share the same core architecture.

Q2: Does A20B-3300-0391 support servo HRV3?

FSSB servo cards like the 039x family support the HRV control modes configured through the servo parameters in the CNC or robot controller. Whether HRV3 is active depends on the system's servo software version and parameter settings — not the servo card hardware itself. Confirm the supported HRV modes from the applicable FANUC maintenance manual.

Q3: Does replacing A20B-3300-0391 require servo parameter re-entry?

No. All servo parameters for the 6 axes reside in the CNC's or robot controller's main SRAM. After fitting the replacement A20B-3300-0391, the system reloads all parameters automatically. Verify correct servo response at low speed on all 6 axes before returning to full operation.

Q4: Can A20B-3300-0391 be used in an R-30iA or R-30iB robot controller?

The A20B-3300-0391 is confirmed for "B Generation i CNC / Robot." The R-J3iB controller is the primary confirmed robot platform. For R-30iA (R-J3iC) and R-30iB platforms, confirm from the applicable robot controller hardware manual whether 0391 is listed as the supported servo card — later platforms use updated servo card generations.