I have a weird issue.... My 11" 2 GHz i7 8GB 256 GB SSD (the best 11" air you could buy in 2012 I think) Just won't boot...

I have a weird issue....my 11" 2Ghz i7 8GB 256gb ssd 1536 video memory (the best 11" air you could buy in 2012 I think)...

Hmm. If you're positive the screws are tight then this definitely sounds like the “clutch" inside the top lid assembly is worn out most likely. It's a decent size job so it may or may not be worth the time and effort. Basically depends on your level of expertise and cost of parts vs age of machine. It might be worth just using as is until you can find another machine. Good luck either way. Here's a link on replacing the top lid “clutch". https://youtu.be/L05t8gPsf2Q

It REALLLLLY sucks that this external case (CASE) is 100.00! When for a standard M.2 you can buy a 2.5" enclosure and simy reuse the drive in any PC but Apple's.dam proprietary style ssds make this irrelevant until.someone in China makes one which I'm sure won't be long. I want to put my 128gb INSIDE an older.2012 2.5" standard HD machine....granted it won't be quite as fast it'll still be better than an external option which I don't need at all.

Always use a bit of locktite on each display hinge screw (,the ones that tighten the slack) so they don't back out again later. If you find the triangle hinge screws tight but still display is a bit loose you can cut a couple pieces if thin rubber to put under that hinge piece on each side and then screw it down. You do NOT have to replace the whole display necessarily as suggested. That's bogus....

Absolutely do not replace the logic board, that is a very fast logic board as it is and you have fast Ram as well, all you need to do is put a solid state hard drive in it and call it a day. You don't even need to do the Dual raid setup and it would still be 15 to 20 times faster than it is now but rating a couple of solid state drives would certainly give you even more but it's not worth buying a new logic board for a very very unnoticeable only slight boost in performance. The solid state hard drive will give you much more performance by a long shot then replacing the board with an i7 processor that's going to cost you three times as much as a couple of hard drives and a mounting bracket for the second one. So definitely leave the board alone you also risk of damaging the unit if you don't know how to replace the board anyway and you definitely don't want to do that so just slap a large solid state hard drive in it or two of them if you want to give up the DVD drive and call it a day that thing will...

You'd be better to get a new dual band usb AC wifi/bluetooth 4.0 combo dongle for a little more (prob about 50.00 and this antenna only is 27 and tax plus shipping and also used.....) and you'd have AC wifi and newer Bluetooth, but it is a usb connection instead of internal so unless you REALLY want internal only you'd gain much more with a newer AC wifi/BT 4.0 dongle for a few bucks more.

It sounds like a logic board issue but you also stated you touched the thermal connector and its disconnected...if that's the case you'll definitely get a Veep code and no boot as the Mac us essentially protecting itself. Make sure EVERYTHING is reconnected. RAM will always produce a 3 beep pause, 3 beep pause over and over so a single Veep,is not the RAM. Make sure the data connector to the logic board didn't pull out when you swapped the drive, did any fan connectors come loose? The newer Mac minis have a fan connector that can be ripped off the logic board very easily if you lift the assembly up to high before removing it, it's very, very touchy and easy to come unsoldered from the logic board by a simple wrong touch. I pulled mine out very, very, very carefully and it still came. Loose took the receiver clip off the logic board with it when I tried to unplug it, which is a horrible design, I'm not sure if the older ones have this or not, but you have to make sure every single cable is re plugged in or...