From fit-PC wiki
1. Fit-PC4 BIOS reset:
- Power down the PC and unplug the power cable.
- Open the service door (by screwing out one bolt) and remove it (with the storage).
- Remove the memory SO-DIMM modules.
- Reset the BIOS by shorting two test points (TP40 and TP41) for 3 seconds located between memory slots close to an edge, as shown in the picture below.
- Install back the memories + the storage with the service door.
- Plug the power and power up the PC (either auto-on or pressing power button).
2. Verify RAM memory modules are installed -
- The system will not boot without memory.
3. Using single RAM memory module with fit-PC4:
- Issue: When single RAM memory module being used on inner memory SO-DIMM slot (P6) it may cause the system not to pass memory initialization process.
- Fix: In case single RAM memory module being used, it should populate the SO-DIMM slot closer to an edge (P7) of the PCB.
4. Try to answer the following questions:
- Are you able to power up without storage?
- What type of storage being used in terms of RPM (in case of HDD)?
- Note that 7200rpm drives are not recommended due to lower power nature of the PC, as such drives used to overload the machine. 5400rpm drives at maximum must be used.
5. Power supply:
- 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.