Hi Giamma,
Such issue can be caused because of loose connection of the hardware components. Please try draining the residual charge from the system. Here are the steps:
- Disconnect any external peripherals (flash drives, printers, external hard drives) from the computer.
- Then remove the power supply.
- Press and hold the power button for 20 seconds.
- Reconnect the power supply only.
- Try to restart the computer and check functionality.
The Diagnostic LEDs pattern 123 indicates following errors:
- If a hard drive is installed, reseat the drive’s power and data cable connectors and restart the computer.
- If a NVRAM is installed, reseat the NVRAM module and restart the computer.
- If there is an error message on the screen identifying a problem with a device (such as the hard drive), check the device to make sure it is functioning properly.
- If the operating system is attempting to boot from a device (such as a CD/DVD drive), check BIOS settings to ensure the boot sequence is correct for the devices installed on the computer.
Please refer to the Service Manual and reseat the components firmly. Please follow the safety instructions mentioned on the manual.
Hope this helps. Please reply with the results.