Thank you for contacting us regarding the boot issues that you are facing with your NUC6CAYH, it will be more than a pleasure to help you out.
Your case captured our attention since the behavior of both units (old one and replacement) is not normal, especially after all The troubleshooting that you performed, we really appreciate your patience and commitment when following all of our troubleshooting articles.
Since you basically tried everything, there is one thing left that could be the reason of the behavior of your unit.
There are few models of RAM memories that sure no supported by our NUCs even if the meet the requirements that we specify in our compatibility list of peripherals:
On the link above you will find the list of tested peripherals for your unit, feel free to check it.
Based on the description of your issue, we suspect that the density of your RAM could be part of the issue since the processor on these Intel NUC models support only DDR3L memory modules with 4 Gbit or 8 Gbit technology.
If by any chance the memory module that you have installed uses either 1 or 2 Gbit (gigabit) technology, the unit will show system instability.
Please go ahead and compare your RAM with the ones displayed on this article: https://www.intel.com/content/www/us/en/support/articles/000023485/mini-pcs/intel-nuc-kits.html
As well please attach pictures of your Memory in order to perform further investigation.
By any chance, have you tried to boot the unit with a different RAM kit?
I hope to hear from you soon.
I was taking a look to your thread, and I wanted to confirm if you need further assistance?
Please do not hesitate on replying back so we can provide you with assistance regarding your issue.
I hope to hear from you soon.
the first NUC I have tested with one different memory module (4GB that meet the specification) and the behavior was the same. Won't turn on. I suppose it should boot into the bios with one 4GB memory module that meets the specification? Or do I need two memory modules to be present?
I have ordered the third replacement NUC, however the behavior is still the same. The last what I can try is to replace memory module. Unfortunately, I don't have any device that uses DDR3L-1600 SO-DIMM to test that the module is defective. I am enclosing photos of my memory module separately and inserted to the NUC (however it does not work also in the second position).
I will try to buy memory module from compatibility list you sent me.
Thank you for your response, I really appreciate it.
I will wait for you buy memory module from compatibility list since there is a chance that the module that you own is defective, due to the fact only one memory should be able to boot the BIOS of your machine.
I’ll follow up in 5 days, if you get it sooner, do not hesitate on reaching me.
I just wanted to confirm if you need further assistance?
Please do not hesitate on reaching us back in case that you still need help.
I can confirm that after installing Kingston KVR16LS11/4 memory module, the device is working.
I had some issues that HDMI audio does not work out of the box. However after installing firmware and configuring audio manually by the script on startup
xrandr --output HDMI-1 --set audio on
the audio is also working. I can also confirm that wifi is working under Debian Stretch when the firmware is installed.