From fit-PC wiki
I can't turn on the computer, it doesn't wake up?
- Pay Attention under each section to it's LED behavior for further diagnostics.
1. Check power supply (PSU)
- Verify the power supply is not damaged and functions properly.
- If you have another power supply use it to eliminate and determine the failing side.
- In case you use other power supply make sure it provides uninterrupted power and stable grounding.
2. Check memory (RAM)
- Verify RAM modules are installed. The system will not boot without it.
- Also Swapping DIMMS with a good known working ones could eliminate memory stick issues.
LED-R (RAM) This LED turns Green, the moment the memory initialization is successful. This LED is Yellow while the memory initialization is in progress. If the memory initialization has failed, for example: There is no DIMM installed / the DIMM is not supported - the R LED will stay Yellow. The R-LED should stay Green at normal operation, also after BIOS POST is over.
3. Check Peripherals (HDD/SSD/USB)
- Unplug peripherals and try to power up with bare minimum, that includes HDD/SSD/USB devices.
- Verify power up without storage. Sometimes damaged drives may cause the overall system to malfunction.
4. Airtop2 BIOS reset
- Power down the PC and unplug the power cable.
- Open the service door.
- Remove the disks cartridge.
- Reset the BIOS by pressing the low profile push button SW1 (RTC_RST).
- Mount the disks cartridge and close the door.
- Plug the power and power up the PC (either auto-on or pressing power button).
LED-B (BIOS) This LED is Yellow after display initialization. If BIOS setup menu is needed, the DEL button is functional from the moment the B-LED is Yellow. The B-LED is Green when the OS takes charge of the system.