xbox 1 s HDMI repair

That would entirely depend on where you take to get it serviced. If you want it done firsthand by Microsoft, the requisite link can be found here:

https://beta.support.xbox.com/help/hardware-network/warranty-service/getting-your-product-serviced

Great, there are 2 HDMI port on the console, make sure that you're using the one that says HDMI OUT to TV, also you're mentioning something about a 4K TV, remember that the Xbox one S does not support 4K, now if you have tried this and the issue is persisting,
after trying a different HDMI cable and a different TVs, I'd recommend you to check the warranty status of the console on account.microsoft.com/devices, remember that all Xbox one consoles comes with the benefit of 1 year of warranty, if the console is still
on warranty, place a repair order for the console to get it repaired as soon as possible!

You sue you got your Xbox One S plugged into HDMI 1? some TV's only display 4K over HDMI 1.

Do mean no HDMI output from your console ?

If so then it`s possible the HDMI port has gone faulty. It`s quite a common problem with consoles that are regularly being unplugged and plugged back in.

Their are plenty of PC repair shops who also specialise in console repair. I`d take it to your nearest and get it checked out.
And it`s not against Microsoft T`s & C`s to get a faulty console professionally repaired. It`s only against T`s & C`s to make illegal modifications.

Wouldn't this be one of the examples as to how to utilize the Xbox 1's HDMI input?