You power the machine on, the Fanuc logo or boot text appears — and it just sits there. A control frozen during startup is almost always one of a short list of causes. Work through this checklist in order before assuming the worst.
1. Remove anything in the memory card slot
The single most common cause we see: a CF/SD memory card left in the front slot. Depending on boot settings the control tries to boot from the card and hangs. Power off, remove the card, power on. If it boots — that was it.
2. Power-cycle properly and give it time
Switch off at the main breaker, wait 30 seconds, power on and wait a full two minutes. Some option-board configurations legitimately take a while on the initial screen. One clean cycle rules out a transient.
3. Read the LEDs
Open the cabinet and look at the control's boards: most Fanuc main boards have status LEDs or a 7-segment display that steps through codes during boot. Note where the code stops — that number identifies the stage (and often the board) where boot halts. Photograph it; it's the single most useful thing you can tell a repair engineer.
4. Reseat boards and connectors
Power off and locked out: reseat option boards, the display/video cable, and inter-board connectors. Oxidised or half-seated connections after years of vibration stop boots surprisingly often — especially after someone has recently worked in the cabinet.
5. Suspect corrupted memory (FROM/SRAM)
If boot halts at the same point every time and LEDs point at the memory stage, the FROM/SRAM contents may be corrupted (dead battery history is the classic cause). Recovery via the boot monitor and a restore from backup is possible — but a wrong move here can erase the machine's soul. If you have no backup, stop and get help before experimenting.
6. Hardware failure
Remaining suspects, roughly in order: power supply (verify the DC voltages), the main CPU/motherboard, an option board, or the display unit itself (a machine that actually boots but shows nothing looks identical — check whether the machine responds, fans spin up, and reference our display troubleshooting guide). All of these are repairable or replaceable at board level.
Related
WhatsApp us a photo of the frozen screen and the board LEDs — we'll tell you what stage it's failing at and quote the fix. Board-level repair, free diagnosis, warranty.
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