If your CNC control screen is flickering, dim, burned-in, or takes ten minutes to warm up to full brightness — it's dying. CRT monitors in machine tools are typically 20–30 years old now, and replacement CRTs are no longer manufactured. The good news: modern LCD replacements are brighter, lighter, and draw a fraction of the power.
Here's how to identify what's wrong, pick the right replacement, and get it installed without losing parameters or reference positions.
⚠️ Safety First — Before You Touch Anything
The CRT in your CNC control contains a high-voltage flyback transformer that can hold a lethal charge even when the machine is powered off. If you're not qualified to discharge a CRT safely, do not open the monitor housing. The LCD replacement process itself is low-voltage — the danger is in the old CRT you're removing.
- Lock out and tag out the machine at the main isolator before opening any panel
- Wait at least 30 minutes after powering down before touching any CRT internals — capacitors in the monitor can hold 15,000V+
- Never work alone on CRT removal. Have someone nearby who knows where the emergency stop and main isolator are
- If you're unsure about any step, have a qualified machine tool electrician handle the CRT removal. The LCD installation is straightforward — the dangerous bit is getting the old CRT out safely
Is Your CRT Actually Dying?
Not every display problem means the CRT has failed. Run through this checklist before ordering a replacement:
| Symptom | Likely Cause | Fix |
|---|---|---|
| Screen takes 5–30 minutes to reach full brightness | CRT tube aging — the cathode is worn | CRT is end-of-life. Replace. |
| Permanent ghost image burned into screen | Phosphor burn-in from static display | Cannot be repaired. Replace. |
| Flickering or intermittent picture | Loose video cable, bad solder joint on CRT driver board, or failing flyback | Check connections first. If connections are solid, it's the CRT electronics — replace. |
| Screen completely dead, no glow | Blown fuse on monitor PSU, failed flyback, or dead tube heater | Check the monitor's internal fuse first. If fuse is good, the CRT has failed. |
| Dim but stable picture | Brightness/contrast pots worn, or aging tube | Try adjusting pots. If it won't reach acceptable brightness, tube is worn — replace. |
CRT Repair vs LCD Replacement — The Cost Reality
Nobody manufactures replacement CRT tubes for CNC controls anymore. A "CRT repair" typically means replacing capacitors on the driver board or sourcing a used tube from a dismantled machine — and that used tube is just as old as yours.
| CRT Repair | LCD Replacement | |
|---|---|---|
| Cost | £600–1,200 if you can find a technician | £245–595 for a plug-and-play kit |
| Downtime | 1–4 weeks (send away for repair) | 30–60 minutes on-site |
| Result | Same dim, ageing tube with new electronics | Bright, crisp LCD with no burn-in |
| Power draw | 60–120W | 5–10W |
| Warranty | Typically 30–90 days | 12 months standard |
| Future-proof | No — CRTs are extinct | Yes — LCDs are replaceable and available |
The maths is simple: for less than the cost of a CRT repair, you get a brand-new LCD that'll outlast the machine.
Which Screen Fits Your Control?
LCD replacement screens are designed as drop-in kits for specific control models. The screen must match the electrical interface and physical mounting dimensions of your original CRT. Here are the most common ones:
Fanuc Controls
| Original CRT | Common Controls | Replacement |
|---|---|---|
| 9" monochrome (A61L-0001-0076, 0086) | Fanuc OT, OM, 6T, 6M, 10T, 11M | 9" LCD — £245.45 → |
| 9" colour (A61L-0001-0093) | Fanuc 15, 16, 18 | 9" Colour LCD — £255 → |
| 14" CRT (A02B-0092-C200, C14C-1472) | Fanuc 18M, 21 | 14" LCD — £495 → |
| Older 9" (A61L-0001-0072) | Fanuc 3, 5, 7 series | 9" LCD — £315.45 → |
Mazak Controls
| Original CRT | Replacement |
|---|---|
| 14" CRT (CD1472D1M) | 14" LCD — £485.50 → |
| 12" CRT (AIQA8DSP40) | 12" LCD — £475.55 → |
Haas / Heidenhain
| Original | Replacement |
|---|---|
| Haas 14" (28HM-NM4) | 14" LCD — £425.45 → |
| Heidenhain 10.4" (BE212) | 10.4" LCD — £595.45 → |
Not sure which screen you need? Take a photo of your control panel and the label on the back of the CRT. Send it to us → and we'll identify the correct replacement.
What's Included in an LCD Kit?
A proper LCD replacement kit should include:
- The LCD panel — industrial-grade, not a consumer monitor
- Mounting bracket — designed to fit the original CRT mounting points
- Video converter board — converts the CNC's video signal (CGA, EGA, or VGA) to the LCD's native input
- Power supply — typically taps into the control's 24V DC or 110V AC
- Cables — pre-terminated to match your control's video connector
Installation Overview
Installation typically takes 30–60 minutes for someone familiar with machine tool electrics. The basic process:
1. Power down completely. Main isolator off, wait 30 minutes for CRT capacitors to discharge.
2. Remove the old CRT. Unplug all connectors, unbolt the CRT from its mounting frame. The CRT is heavy — have a second person support it.
3. Mount the LCD bracket. Bolt into the original CRT mounting points. No drilling required on any kit we stock.
4. Connect video and power. The converter board connects to the CNC's video output. Power connects to 24V DC or 110V AC depending on your kit.
5. Adjust position and test. Power up, check the image is centred and sharp, adjust brightness/contrast on the LCD's control board.
6. Check parameters. After power-up, verify your machine references correctly and all parameters are intact. The LCD replacement doesn't touch the control's memory, but it's good practice to confirm.
Always back up your CNC parameters before any work inside the control cabinet. See our Fanuc Parameter Backup Guide →
What If You're Not Sure Which Screen You Need?
We stock replacement screens for Fanuc, Mazak, Haas, and Heidenhain controls. If your control isn't listed, or you're unsure which model you have, browse all replacement screens → or send us a photo of your control → — we'll match it for you.