From fit-PC wiki
Fit-PC3 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 RAM memory modules.
- Reset the BIOS by shorting for 3 seconds two test points (TP136 and TP137) as shown in the image 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. 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.
4. 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.