This tech note is a short, quick-reference companion to Tech Note 47 (full LCD troubleshooting guide) for customers who see a display problem specifically at power-on or boot, before the unit has finished starting up.
Quick Triage
- Screen stays completely blank at power-on, no backlight at all — check the main fuse and LED status first (Tech Note 32), then see the Basic section of Tech Note 47 for backlight/connector checks.
- Backlight is on but no text appears, or text is garbled/incomplete during boot — see the Advanced section of Tech Note 47 for display connector and module checks.
- Unit appears to freeze on a boot/logo screen and never finishes starting — this can indicate a firmware or CPU module issue rather than a display issue; verify firmware version (Tech Note 3) and consider whether a CPU module swap (Tech Note 44) is needed.
- Display works fine once fully booted but was briefly garbled only during the boot sequence — this is often cosmetic and related to the display initializing before the processor finishes loading; if it clears up and stays clear, no action is needed.
If the Basic Steps in Tech Note 47 Do Not Resolve It
Contact support with the unit serial number (Tech Note 2), the exact point in the boot sequence where the problem appears, and whether the issue happens every power-on or only intermittently.
