TL;DR: after changing BIOS options to disable Secure Boot and enable Legacy Boot, NUC no longer outputs video. Also, after powering it off by holding the button for 4 seconds, it powers itself back on after about another 4 seconds.
Long version: I was trying to install Fedora Linux 29 and ran into filesystem corruption, which turns out to be an issue with the Intel SSD. Before I found that, I updated the NUC BIOS from 69 to 72 (and everything worked through another attempt at installing Fedora).
Then I downloaded the Intel SSD Firmware ISO and wrote it to a USB thumb drive (dd on Linux). It would load its boot loader (GRUB), but I got blank screens after that. I thought maybe it either didn't handle Secure Boot or needed to boot in legacy mode (rather than UEFI), so I went into the BIOS and changed those options. After saving and existing from the BIOS, the NUC will power on but not display any video on the HDMI port (tried a couple of different monitors).
I wanted to reset the BIOS settings, but there appears to be no battery. I found the document about holding the power button for 3 seconds to get into the special menu, but I still get no video (and the button does not turn amber, it just continues into an apparent regular boot).
I also tried the BIOS recovery by removing the jumper and putting the .BIO image on an otherwise blank (and freshly formatted) USB drive. I tried both 72 and 69, but I can't tell that anything happened, since I still have no video. I let it sit for about 10 minutes, but it never powered off (as the recovery instructions say should happen). I also tried removing the SSD and going through the recovery process again - still nothing. I even tried several different thumb drives (just in case the NUC didn't like one).
I do think that _something_ has changed, as I get the blue ring around the front panel (which I had previously disabled).
Any suggestions, ideas, etc.?
Hello @CAdam11 ,
There is CMOS battery in your NUC. It is located on the board upper side. Therefore it is difficult to reach the battery connector. If you want to do this (and I think that in this case, it is worthy to try), you should remove the board first. I'm giving you link to clip showing how to remove board in similar NUC. Pay spacial attention to disconnect the coaxial connectors of WiFi antennas. The WiFi antennas are glued to the case, so, you you will not disconnect the cables, you may damage the connectors https://www.youtube.com/watch?v=MwqrfIdyvGw&t=300s . In this clip it is shown when you are in 5:07 minutes. You should leave the battery disconnected for 15 minutes.
Try removing all the memory SODIMMs then power up the unit. The power button LED should blink three times then repeat, indicating memory error.
A lack of video during power-up may be related to the memory. Do you have a different DDR4 SODIMM (brand, size, etc.) to try with your NUC?
If I pull the RAM (I'm just using one stick), I do get the power button blink code for bad RAM. Unfortunately, I don't have another DDR4 SO-DIMM on hand to test with. I did try putting the one stick I have in the other slot, but that didn't help.
I tried three different displays (original setup that was working before this problem with A/V receiver and TV, then another TV, then a monitor, all with different HDMI cables).
What brand/model memory are you using?
Earlier today , after reading your post, I pulled both SODIMMs off my NUC7i5BNH to confirm the 3-blink memory error before posting. When I re-installed the SODIMMs, the NUC powered up with no video. Power button LED was solidly lit, but no NUC splash screen on my Acer T232HL monitor over HDMI, and no sign of OS booting up from NVMe SSD either. I then pulled one of the two SODIMMs, and the NUC splash screen appeared followed by the expected "Memory size decrease" notification. I then re-installed the second SODIMM, and everything went back to normal and Win10 booted fine off the SSD. This is possibly either a case of dirty contacts or a peculiarity in the NUC UEFI code detecting two of my SODIMMs after a "no memory" error.
I'm using Samsung 4GB 1Rx16 PC4-2400T M471A5244CB0-CRC SODIMM pairs with several of my NUCs. With the NUC7i5BNH this SODIMM runs at 2133 speed.
I do like to use DeoxIT Gold contact cleaner on the gold fingers of SODIMMs before installing them. I'm convinced those tiny contacts are very susceptible to contamination compromising the electrical integrity.
I have a Corsair Valueselect 16G SO-DIMM. I've swapped it between sockets with no change. I don't have another DDR4 SO-DIMM or another device with a DDR4 SO-DIMM socket to test (work notebook is older and is DDR3, personal notebook is DDR4 but soldered in).
I don't have any kind of contact cleaner on hand right now to try that.
Intel has apparently flagged the Corsair CMSO32GX4M2A2133C15 (16GB x 2 kit) as incompatible with NUC7i5BNK:
Instability, monitor flickering, monitor blanking reported with Corsair CMSO32GX4M2A2133C15 memory. SPD data is not correct
Corsair ValueSelect 16GB SO-DIMM is CMSO16GX4M1A2133C15 which looks like the same module used in the 16GB x 2 kit, so you may well be using an incompatible module with your NUC. Trying another brand of DDR4-2133 SO-DIMM should hopefully shed some light into your scenario.
That doesn't mean there is nothing wrong about those memory modules.
If the memory started flaking out gradually a while back then got aggravated by changing settings or updating the BIOS, there may be multiple issues combining to result in no video.
My gut feel is that you may not achieve a breakthrough until you try memory other than the Corsair you have. That memory may be undermining your recovery efforts in some way.
A recovery procedure may be something like this: