Fixing HoloLens 2 headband adjustment knob falling off

HoloLens 2 is a device of very high build quality, and very, very rarely something goes physically wrong with it if you handle it with proper care. However, a few weeks ago, I actually had this little problem happening:

This does not affect HoloLens 2 use, and you can still adjust the head band, but the knob does not stay put in it’s place anymore, which can be a bit bothersome. Yet nothing seemed to be broken (and nothing was, I found in the end).

If your device is still under warranty, you might want to have it replaced by Microsoft, but if it is not - or, if you are like me, simply impatient: you can actually repair this yourself. It’s not hard. But please first read the entire procedure, including the disclaimer.

Step 1: separate knob front and back part

The point is, the knob is made out of three parts. First, you have got to separate the front end and the back end by counter-rotating them. I think I recall you have to rotate the front part on this image counter clockwise while holding the back end in place.

Step 2: pull off the middle part

Step two is to pull this part off

Just gently pull it forward and then we have this. Note there is some grease on parts B and C. Be careful to get at as little on your fingers as possible. This grease is there for a reason. Don’t clean it away from the parts.

Step 3 connecting part A and B back to the HoloLens

Now comes the tricky part, which I don’t have pictures of, alas: put part A over the hole in the back of the battery pack

Narrow end first. Then push part B trough it, with the tree little clamps first (and the dirty greasy end to the back) Now try to rotate part B clockwise (if I remember correctly) until you hear a click. I think some specialized tool exists for this, I just pushed a bit with the back of a pair of tweezers.

Then put it part C, pointy end first. Now you have to find a way to rotate part A so part C is screwed fest again. I used my fingers and the same pair of tweezers.

Step 4: clean you hands and the HoloLens

Final step: clean your hands and the back of the HoloLens, that both now probably have some grease over it.

Final thoughts and disclaimer

Don’t force anything if it doesn’t work out. I might have mixed up clockwise and counter-clockwise in the heath of the moment, and I am not going to try to disassemble my HoloLens again to check it out for real 😉. This problem happens very rarely, and mostly only on HoloLenses who have seen a lot of use. However, a fellow MVP, having encountered the same issue, reported succesfully applying this procedure. Unfortunately he also could not quite remember when exactly clockwise or counter clockwise was used. The way the little clamps on part C are oriented should give you some clue.

Disclaimer: this is not an official procedure, it is not sanctioned by Microsoft or anyone else, including me. YMMV. Use this procedure at your own risk.