Siemens Sinumerik 810T/820T CRT to LCD Upgrade β Complete Guide
Overview
The Siemens Sinumerik 810T and 820T are among the most widely used CNC controls in European machine tools β found on Deckel Maho, Hermle, DMG, and many other German-made machines. These controls use 9-inch monochrome or color CRT displays that are now well past their design life. If your 810T or 820T display is fading, flickering, or dead, an LCD upgrade is the most cost-effective solution.
β Important: Unlike FANUC and Mitsubishi which use DC 24V, Siemens Sinumerik CRTs operate on AC 110V or AC 220V. Our LCD modules include a built-in wide-range AC power supply compatible with both voltages. Confirm your machine voltage before ordering.
Compatible Siemens Models
| Siemens Control | CRT Module | Screen | Connector | Power | LCD Kit |
|---|---|---|---|---|---|
| Sinumerik 810T (GA2/GA3) | 6FC3988-7FA20 | 9" monochrome | DB-25 | AC 110/220V | KTO-SI9M β $399 |
| Sinumerik 820T (GA2/GA3) | 6FC3988-7FA20 | 9" monochrome | DB-25 | AC 110/220V | KTO-SI9M β $399 |
| Sinumerik 810T GA3 | 6FC3988-7FA21 | 9" monochrome | DB-25 | AC 110/220V | KTO-SI9M β $399 |
| Sinumerik 820T (late) | SM0901-579417TA | 9" monochrome | DB-25 | AC 110/220V | KTO-SI9M β $399 |
| Sinumerik 810D/840D | 6FC4600-0AR04 | 8.4" color | Proprietary | AC 110/220V | KTO-SI8C β $430 |
Identifying Your Siemens CRT Model
To find the correct LCD replacement for your machine:
- Check the CRT label. Look for a sticker on the CRT bezel or rear housing. The OEM part number is usually printed as 6FC3988-7FA20, 6FC3988-7FA21, SM0901-579417TA, or 6FC4600-0AR04.
- Check your control model. The Sinumerik control type is displayed on the machine nameplate or the control panel: 810T (GA2 or GA3), 820T, 810D, 840D.
- Take a photo of the CRT label and send it to [email protected] β we will confirm compatibility within 24 hours.
CRT vs LCD Specifications
| Specification | Original Siemens CRT (6FC3988) | Kongto LCD Upgrade |
|---|---|---|
| Display Type | 9" monochrome CRT | 8.4" industrial TFT LCD |
| Resolution | 640Γ400 (CRT) | 800Γ600 (LCD) β 2Γ sharper |
| Brightness | 100β150 cd/mΒ² (degrading) | 400 cd/mΒ² (constant) |
| Lifespan | 10,000β20,000 hours | 50,000+ hours |
| Power | AC 110/220V, 60W | AC 110/220V, 15W |
| Connector | DB-25 (25-pin D-Sub) | DB-25 (25-pin D-Sub) |
| Weight | ~6 kg | ~1.2 kg |
| Installed CRTs in field | 50,000+ units (est.) | Direct replacement |
| Warranty | None (end of life) | 2 years |
Installation Guide
Installing the LCD upgrade on a Siemens 810T or 820T takes approximately 30 minutes. No special tools, no CNC parameter changes, no wiring modifications.
Tools Required
- Phillips screwdriver (#2)
- Flat-head screwdriver (for wire terminals)
- Voltage tester (safety check)
Step-by-Step
- Power off completely. Turn off the Sinumerik control using the main power switch. Unplug the AC power cord. Wait 3 minutes for internal capacitors to discharge. Use a voltage tester to confirm zero voltage at the CRT power input.
- Remove the CRT bezel. The CRT is mounted behind a front bezel secured by 4 screws. Remove the bezel carefully.
- Disconnect cables. Unplug the DB-25 signal cable from the CRT rear. Disconnect the AC power wires (note or photograph the wire positions β neutral, live, ground).
- Remove CRT. The CRT unit is typically held by 4 mounting screws in a metal bracket. Support the CRT weight (~6 kg) as you remove the last screw, then lift it out.
- Mount LCD module. Position the LCD module in the same bracket. The mounting holes align with the standard Siemens CRT mounting pattern β no drilling required. Secure with the original screws.
- Connect cables. Connect the DB-25 signal cable (keyed, fits one way only). Connect AC power wires (line, neutral, ground). The LCD module has a standard 3-pin terminal block β match wires to markings.
- Test. Reconnect AC power and turn on the machine. The LCD should display the Sinumerik boot screen immediately. Use the OSD menu (buttons on the LCD) to adjust brightness and contrast if needed.
Signal Pinout β Siemens DB-25 to LCD
The Siemens 810T/820T outputs a standard RGB video signal through a DB-25 connector. Our LCD module accepts this signal directly β no converter or adapter needed.
| DB-25 Pin | Signal | Color | Notes |
|---|---|---|---|
| 1 | Ground | Black | Signal common |
| 2 | Red Video | Red | Analog RGB (0.7V p-p) |
| 3 | Green Video | Green | Analog RGB (0.7V p-p) |
| 4 | Blue Video | Blue | Analog RGB (0.7V p-p) |
| 5 | Horizontal Sync | White | TTL level |
| 6 | Vertical Sync | Yellow | TTL level |
| 7β25 | Ground / Shield | β | Various grounds and NC pins |
Common Issues and Troubleshooting
No display after installation
- Verify AC power is present at the LCD module input (use voltage tester)
- Check DB-25 connection β ensure it is fully seated and screws are tightened
- Confirm the CNC control is booting (listen for relay clicks, check control panel LEDs)
Display flickers or scrolls
- The LCD auto-detects the video signal format. If scrolling occurs, the control may be outputting a non-standard refresh rate. Contact us for configuration assistance.
Display too dim or too bright
- Use the LCD OSD (on-screen display) buttons to adjust brightness and contrast. The OSD is accessed via buttons on the LCD bezel.
Green rectangle on screen
- This is a known Siemens 810T/820T boot behavior where the control outputs a green background before loading the operating system. It is normal and disappears once the control software loads.
β Safety note: Siemens Sinumerik CRTs contain high-voltage components (anode at 10-15 kV). Do not attempt to open or repair the CRT yourself. Discharge time: at least 3 minutes after power-off.
Repair vs Replace β Cost Analysis
| Option | Cost | Downtime | Result |
|---|---|---|---|
| CRT repair (tube replacement) | $400β$600 | 3β10 days | Temporary fix β CRT will fail again (6β18 months) |
| Used CRT (surplus market) | $150β$400 | Varies | Unknown condition β may fail immediately |
| Kongto LCD upgrade | $399 | 30 minutes | 50,000+ hour lifespan, 2-year warranty |
The 810T and 820T CRT has been discontinued by Siemens for over 15 years. OEM replacements are not available. Used CRTs from surplus dealers are themselves 15β25 years old and failing. An LCD upgrade is the only practical long-term solution.
Why Siemens 810T/820T LCD Upgrade Makes Sense
- Price: $399 vs $400β600 for CRT repair that only lasts 6β18 months
- Installation: 30 minutes, plug-and-play, no Siemens parameter changes
- Quality: 800Γ600 LCD vs 640Γ400 CRT β text is significantly sharper and more readable
- Safety: No high voltage (15W vs 60W, no lethal anode voltage)
- Warranty: 2 years vs zero warranty on CRT repair
- Availability: In stock, ships within 48 hours from Shenzhen, free worldwide shipping
Get a Quote
To confirm compatibility with your specific Siemens Sinumerik model, send a photo of your CRT label to [email protected]. We respond within 24 hours.
Available models:
- KTO-SI9M β 9-inch monochrome replacement for 6FC3988-7FA20/7FA21, SM0901 β $399
- KTO-SI8C β 8.4-inch color replacement for 6FC4600-0AR04 β $430
Email: [email protected] | Phone: +86-13686889647