High Pressure Article A20B-8100-0962 A2OB-81OO-O962 A20B81000962

A20B-8100-0962 | FANUC LCD Inverter Card — CNC LCD Display / 0–40°C / 80% RH / Backlight Power Supply PCB

What an Inverter Card Does in a CNC Display

The LCD panel in a FANUC CNC operator interface requires two things to produce a visible image: the video signal from the CNC (which defines what to display) and the backlight behind the panel (which provides the light that makes the image visible to the operator).

The video signal comes from the CNC's display controller board. The backlight power comes from the inverter card.

FANUC CNC displays in the era when the A20B-8100-0962 was designed use CCFL (Cold Cathode Fluorescent Lamp) backlights. CCFL lamps require high-frequency, high-voltage AC power to operate — typically 500V or more at 40–100kHz. The CNC's DC power supply cannot directly drive a CCFL. The A20B-8100-0962 is the circuit that performs this conversion: it takes the low-voltage DC supply from the CNC and generates the high-frequency, high-voltage AC output that drives the CCFL backlight.

When the A20B-8100-0962 inverter fails, the LCD panel's backlight extinguishes — the display appears completely dark or very dim, even though the CNC is running normally. The image is technically still being generated by the video circuit, but it is invisible without backlight illumination.

Key Specifications

Operating Environment Specifications

The A20B-8100-0962 is rated for operation in the same environment as the CNC control unit it serves:

Temperature (0–40°C): The CNC control cabinet's cooling system maintains the internal temperature below the 40°C operating limit. If the cabinet cooling fails — fan stops, air filter blocks — the internal temperature can rise above this limit, risking the inverter alongside other boards.

Humidity (≤80% RH, non-condensing): The non-condensing requirement is important. Condensation on the inverter card's high-voltage output section can create conductive paths that cause arcing, tracking damage, or component failure. CNC installations in humid environments (casting shops, press shops) should ensure the cabinet's positive pressure and sealing prevent moist air ingress.

Altitude (≤1,000 metres): Above 1,000 metres, the reduced air density affects the thermal management of the inverter's high-frequency switching transistors. Standard-rated inverters are not recommended above this altitude without confirming suitability with FANUC technical documentation.

Application Scenarios

CNC display dark on power-up: A FANUC CNC control unit powers on normally — all axes respond, programmes run, alarms are present on the internal CNC state — but the operator panel display is completely dark. Pressing buttons generates CNC responses confirming the CNC is running. A test with an external light source shows a faint image on the LCD, confirming the LCD panel and video circuit are intact but the backlight has failed. The A20B-8100-0962 inverter card is replaced. The display returns to full brightness.

Intermittent display dimming: A CNC operator panel display occasionally dims significantly before returning to normal brightness. The symptom worsens as the machine warms up. The A20B-8100-0962's inverter components show temperature-related degradation. Proactive replacement prevents a full backlight failure.

FAQ

Q1: How do I distinguish an inverter card failure from an LCD panel failure?

An inverter failure causes loss of backlight — the panel is dark or very dim, but the LCD itself is intact. An LCD panel failure typically causes permanent image defects: dead pixels, lines through the image, or partial display corruption. Test by shining a bright light at the LCD surface at a shallow angle — if you can faintly see a correctly rendered CNC screen, the video signal is reaching the LCD and the inverter is the failed component. If the panel shows distortion or missing areas, the LCD panel itself may be at fault.

Q2: Can the A20B-8100-0962 be used with LED-backlit LCD replacements?

LED-backlit LCD panels do not use CCFL inverters. LED panels include their own integrated LED driver circuit or accept a low-voltage DC signal directly. If the original CCFL LCD is replaced with an LED retrofit panel, the A20B-8100-0962 inverter is typically bypassed or disconnected — the LED panel's power requirements are different. Confirm the connection requirements of the specific LED retrofit before proceeding.

Q3: What causes CCFL inverters to fail over time?

CCFL inverter failure is typically age-related. The electrolytic capacitors in the inverter circuit degrade over time — losing capacitance or developing increased equivalent series resistance (ESR). As capacitor quality degrades, the inverter's oscillation frequency and output voltage become unstable. CCFL lamps themselves also age — their efficiency decreases and starting voltage increases, placing more stress on the inverter. The combination of lamp ageing and capacitor ageing is the most common failure mechanism.

Q4: Is the A20B-8100-0962 a standard CNC spare or a machine-specific component?

The A20B-8100-0962 inverter card is a FANUC part number — it is a standard FANUC CNC component, not a machine-specific part. It appears in multiple FANUC CNC display configurations that use the same inverter hardware. This makes it a stockable spare for facilities maintaining FANUC CNC systems with compatible display units.

Q5: After replacing A20B-8100-0962, is any CNC adjustment required?

No. The inverter card is a pure power supply component — it has no digital interface to the CNC and carries no stored parameters. After fitting the replacement and powering on, the backlight should illuminate immediately without any CNC configuration steps. If the display remains dark after fitting the replacement, investigate the CCFL lamp itself — the lamp may have reached end of life independently.