Sure thing!
I'm going to make this sound instantly less impressive by saying that it's not really that difficult to get in to. I learned everything about it by watching a bunch of youtube videos and thinking "Huh. I should give this a shot". So, I did.
I mainly fix PS4s (so far, I'm up to 25), although I have also fixed a couple of Xbox Ones. I would LOVE to get my hands on some Switches to fix, but for whatever reason, they are very hard to find on ebay for reasonable prices. Maybe they aren't old enough yet to start breaking en masse? Who knows.
ANYWAY
The reason why I prefer fixing PS4s is because they are much easier to diagnose. I don't know if this was by design on Sony's part or if it was a Bob Ross Happy Accident, but every kind of fault on a PS4 (Except for one) points to a specific issue. If it turns on and you get a White Light on the console but nothing showing on the display, it's a HDMI circuit issue. If the console turns itself off after 2 seconds, it's an APU issue, etc. The only fault that doesn't really follow this pattern is when you get a constant, flashing blue light. This is more of a 'General Error Code' thing and, from what I've seen, can mean absolutely anything.
The most common fault that happens (based on the ones I've personally fixed), is a damaged HDMI port. Somebody has used a bit too much force putting a cable into it and bent a pin, that kind of thing. Luckily, this is also the 2nd easiest thing to fix because it's just a case of taking the old port off and putting a new one on, which takes about 20 minutes. The easiest thing to fix is when someone sells their console as faulty because it overheats and turns itself off. This is just a case of taking it apart and clearing all the dust out of the fan/heatsink and then putting it all back together.
The downside of buying things off of ebay though is that you never REALLY know what you're going to be getting. 'Console doesn't turn on' is usually just a bad power brick, but I've had consoles arrive where I've actually said out loud, to myself "What the fuck is this shit?" when I've opened it. The seals on the back were intact, but they'd used a hammer to smash the securing screws out, denting the protective metal shielding around the motherboard, all so they could try (and fail) to replace the HDMI port themselves. How I brought that particular console back from the dead is beyond me.
https://imgur.com/d5Q7YVp - I mean, look at this shit. Did this port owe them money or something?
