Siemens 6FC3998-7FA20 LCD Replacement Guide
June 2026 | Kongto Technology | Compatibility Matrix
Overview
The Siemens 6FC3998-7FA20 is a 12.1-inch monochrome CRT display used in SINUMERIK 810 and 820 series CNC controls. These are European-made CNC systems from the late 1980s and early 1990s, still widely used in European manufacturing facilities.
Critical: Power Supply Difference
Unlike Japanese CNCs (FANUC, Mitsubishi, Mazak) which use DC 24V for their displays, Siemens SINUMERIK 810/820 CRTs use AC 110V power. Ordering a DC-powered LCD for a Siemens machine will result in immediate damage to the display. Always verify you have the correct AC 110V version before connecting.
Connector Type
Siemens SINUMERIK CRTs use a DB-25 (25-pin D-Sub) connector. This is different from the Honda MR-20M (FANUC) and 20/26-pin (Mitsubishi/Mazak) connectors used by Japanese CNCs.
Installation
- Verify your power supply is AC 110V (measure with multimeter if uncertain)
- Power off CNC completely
- Remove old CRT unit
- Disconnect DB-25 connector
- Connect DB-25 cable to new LCD
- Mount LCD in original position
- Power on
Compatible Models
- Siemens SINUMERIK 810
- Siemens SINUMERIK 820
- NFP SM0901 (579417 TA) β same connector and power
Need a replacement?
Email szkongto01@foxmail.com with your CNC model and a photo of your current display. Free compatibility check and same-day quote.