No, I only use my TV as a monitor, so I don't think that is it.
After I made my post I have also tried to move the BIOS jumper, but without any luck.
even so, what if u did select 2nd screen only, then that may cause nothin to display on your monitor
Before replacing the NUC, I suggest you to perform a test using the kit, 1 memory stick, HDMI cable, no SSD. Make sure the video input of the TV is set to HDMI.
If it works, you will be able to get into the BIOS. Otherwise, contact the support team for replacement.
The processor Base Frequency of Core™ i5-3570 is 3.4GHz. 1 or 2 Cores will reach 3.8GHz with Turbo Boost. Now, motherboards have the option to overclock or set the 4 Cores at 3.8GHz.
I suggest you to set the processor multiplier to 100% in the BIOS, verify if processor speed in the BIOS is set to 3.4GHz.