iMac 21.5" Mid2011 strange defects

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I got a cheap mid2011 iMac for parts - just for fun wanted to figure out what is wrong with that machine.
So it is basically unusable, no wifi, no bluetooth, no USB and no Thunderbolt to get all of that back externally.
Everything else works tho. Interestingly enough the camera works.
Tomorrow I will open that thing to see if there is even a BT and wifi module still in there, but the guy I've got it from said he only removed the HDD.
Luckily Firewire worked so I booted from there. The ethernet works too so I could screen share my way in.
I stressed the GPU a bit to see if it works because that is what I'm after.
But it really puzzles me that it seems the machine was fried but still runs well actually. The CPU held up a couple of Cinebench runs too - so no damage there (it seems).

Have you guys any idea what the problem might be on the logic board? At first I thought the USB hub IC is dead but TB is dead too (also no display signal). The camera seems to be on another USB channel than the I/O hub. I'm really curios to see if the wifi module is actually in there (no info in the system profiler).

 

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so ..

I used the machine's GPU to get my 27" running again (works, yay!) I inspected its inards and found a wifi and bluetooth module. I tried the wifi in my 27" and it works.

So what was wonky anyhow is that in the 21" I saw a "switched off" wifi symbol in the status bar but couldn't switch it on (it just stayed off), the system profiler said nothing in the wifi section. I would expect the card to show up as non-existent but it was there but unusable. I guess the BT module is ok too but I had no interest in trying since all I wanted was my 27" to be whole again.

All that says (to me) that either the logicboard is done OOOOORRRRRR the PSU is down on some auxiliary lines.
How do I check that w/o a second PSU
I'd love to confirm if I can reuse the 21" or if I sell it in parts (not the logicboard and PSU of course)