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I just replaced my 6 year old MBP with a new 16" MBP which requires the addition of adapters to connect just about anything external. So I got a USB-C hub with HDMI, RJ-45, USB-3.1 and SD card connectors. If it helps, it is from Networx, model no. Y-9115-S. It works, but gets ridiculously hot (40 - 50˚C) with only a USB stick or an ethernet cable plugged in.

No, I am not running ffmpeg on the hub's internal processor.

This happens with the hub on both the left and right side ports. It comes with its own power supply but I don't use it and run the hub unpowered. The hub temperature certainly is a design flaw in a first-generation product, but I wonder if it is normal. Have others experienced the same or is my hub defective?

Peter Kämpf
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  • Talking about design flaws – that hub comes with an external power supply. And is meant as an accessory for a portable computer. What were they thinking? – Peter Kämpf Dec 13 '19 at 09:28
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    I think it's a good sign: heat dissipation works comparing two SanDisk thumb drives with an equal size and power consumption & both attached to an iMac - one in a plastic the other one in an aluminum enclosure. The one made of aluminum is also very warm (~50°C), the other one is lukewarm (physics!), but I don't really wanna know how hot it is inside.... – klanomath Dec 13 '19 at 13:09
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    @klanomath: That is scant comfort for the fact that this thing is converting my battery's energy to heat faster than the computer itself. And just for some signal conversion. – Peter Kämpf Dec 13 '19 at 13:46
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    @PeterKämpf How much power does it draw while in use? ( > About this Mac… > System reports... > Hardware > USB (probably)) – klanomath Dec 13 '19 at 13:51
  • @klanomath: Sorry, tried that already. I only get information on internal devices. The USB controller only gives available current (500 mA), not actual current. I have an ampmeter for USB, but with USB 2 sockets only. No dice. – Peter Kämpf Dec 13 '19 at 15:43
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    Two words: cheap components. See this answer for a similar scenario. This is normal – Allan Jan 08 '20 at 11:55
  • @Allan: Thank you for the link, very helpful! I did not find this question before asking myself, despite a lengthy search. – Peter Kämpf Jan 08 '20 at 17:21

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As usual, the flood of different converters uses only a few board designs, and the most popular one seems to use cheap components, most likely for power conversion from 5V to 3.3V for its internal electronics. A step-down converter (similar to a switching power supply) costs more than converting the excess voltage to heat via resistors, after all.

I have now found a product made by iTeknic (model # IK-UC001) which actually carries a warning that it might heat up to 130 F in use, but so far it has stayed cool in tasks where the other adapters would heat up close to those 130 F. I have not looked inside (yet) but suspect it uses a step-down converter. They cost about 0.1% of the hub's purchase price, after all.

I guess the Networkx hub's external power supply (for a device meant for portable use!) should had been a warning. The iTeknic hub comes without such a power supply.

Peter Kämpf
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