I get that sometimes single chips fail and that's that... replacing the chip is a bit of a PITA. But by now I've come across several boards that work fine and all of the sudden they're dead - as in draw no more power, no red power-light on the hashplate, 0 chips found.
What component actually fails in such cases?
The majority of the time it's the chips themselves the fail, usually 1 chip at a time, and the way these hash boards are made, 1 bad chip will stop the whole hash board from mining, replacing the chip will need a few tools and a bit of skill, there are many topics around here related to that, youtube also has a ton of videos, and if you want the techy stuff - head to Zeusbtc and download the S9 repair manual.
With that being said, if you have no previous experience fixing electronics, it will be very hard to worth with these hashbaords.