Looking Inside GMKtec NucBox3

I thought the GMKtec NucBox3 looked interesting (at least on paper) as candidate ROS brain, so I ordered one (*) for a closer look despite some skepticism. All pictures on that Amazon listing look perfect, I suspected they were all 3D computer renders instead of photos of an actual product. There’s a chance the actual product looked very different from the listing.

The good news: the product is real and for the most part, as depicted in the listing. I find good fit and finish on its plastic enclosure. There is one downside: fingerprints show up very clearly. I had to wipe down the case pretty aggressively for these pictures and I still see greasy smudges. Well, at least you know these aren’t renders! One instance where oily fingerprint smudges are a feature, not a bug.

I see two brass heat-set inserts on the bottom of the case which will be useful for mounting this little box somewhere. They look very small but this is a small lightweight box so it would probably suffice.

Here we also see where actual product differed from product listing rendering. The company website page for NucBox3 showed an access panel to upgrade memory or storage.

But there’s no such access panel on the real thing, and it’s not clear how to get inside without one. Documents in the box consisted of a minimal warranty card in the box and no instruction manual. No matter, the lack of a convenient access panel or a manual shall not deter me from getting inside for a look.

Hiding fasteners under glued-on rubber feet is a common and effective technique. These four fasteners are not symmetrical so, even though the box is a square, we need to remember correct orientation to reinstall.

Without a convenient access door for upgrades, I wasn’t sure what else would differ from listing picture. I was afraid memory and storage would be soldered-in parts, but I was relieved to find they were standard DDR4 RAM and M.2 2280 SSD as advertised. They’re just a tiny bit harder to access without the panel.

Judging by its M.2 keys, we have the option to upgrade this factory-installed SATA M.2 SSD to a higher-performing NVMe M.2 SSD if needed.

What appears to be empty threaded holes (marked with circles) are actually used to secure the CPU heatsink from the other side. (There’s a fourth one under RAM module and not visible in this image.) Four fasteners (marked with squares) secure the motherboard and must be removed to proceed.

The headphone jack protrudes into the enclosure, so we must tilt the mainboard from the opposite side for removal. But we have to be careful because we are limited by length of WiFi antenna wires.

A block of foam keeps WiFi antenna connectors in place, peeling it back allowed the connectors to be released. The antennae themselves appear to be thin sheets glued to the top of the case, similar to what I’ve salvaged from laptops. How securely were they held? I don’t know. I didn’t try to peel them off.

Freed of WiFi wires, I could flip the mainboard over to see a big heatsink surrounded by connectors. As chock-full of connectors as this product already is, I was surprised to see that there are still several provisions for even more connectors on the circuit board. I’m also very fascinated by connectors used here for USB3, HDMI, and DisplayPort. I usually see them oriented flat against the circuit board as typical of laptop mainboards, but without design pressure to be thin, these connectors are standing upright. This is a tradeoff to fit more connectors on the edge of a circuit board, but each connector must go deeper to obtain the necessary mechanical strength to withstand use.

Looking in from the side, the heatsink appears to have a flat bottom. This is good news if I want to mount a different heatsink on this board, possibly with a fan. The flat bottom means I don’t have to worry about sticking out to make thermal contact with other chips or have to cut a hole to clear protrusions. If I want to mount to the same holes, I will have to drill four holes which unfortunately are irregularly spaced but not an insurmountable challenge. All that said, I’m more likely to just point a fan at this heatsink if heat proves to be a problem.

Using this computer as robot brain also means running it on battery power. Nominal power requirements are listed as 12V up to 3A. My voltmeter measured the factory power adapter output at 12.27V. But what can this thing tolerate? I found this chip directly behind the DC power barrel jack, but a search for DC3905 WK1MEG (or WX1MEG) didn’t turn up anything definitive. Texas Instruments has a LP3905 and Analog inherited Linear Technology’s LT3905. Both chips are designed for DC power handling, but neither footprint matches this chip. This might not even be the power management chip, I’m only guessing based on its proximity to the DC barrel jack.

As far as I know, the highest voltage requirement on this PC are USB ports at 5V. On the assumption that nothing on this machine actually needs 12V, then all power conversion are buck converters to lower voltage levels. If true, then this little box should be OK running directly on 3S LiPo power (Three lithium-polymer battery cells in series) which would range from 12.6V fully charged to 11.1V nominal to 10V low power cutoff. I’ll use the power brick that came in the box to verify everything works before testing my battery power hypothesis.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

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