controller fails to power up

I have three identical 61 key Behringer UMX midi controllers that I used to build a home digital organ and the first one I bought years ago, but used sparingly, had been playing up for some time and now has given up the ghost completely. It does not power up and MIDI-OX software fails to see it. I swapped the board with one of the others. The keyboard now works but the other one with the defective board now fails to play - so it must be this board which is at fault.

This is the instrument when I was still building it.

It has been very difficult to find a replacement of its main board and buying another is a bit out of my budget. Behringer also no longer produce this type anymore and I do wish to preserve the aesthetics of three identical keyboards (keys don't all look the same between different makes). Online, I found keyboards that are horrendously expensive. Locally the only one that seems to suit me best and the cheapest I could source is Eur145.

I tried to identify the culprit component and thought it was one of the diodes as it showed readings both ways unlike the other 3 but on taking it off the board, which was not easy, it worked as expected. I tried soldering it back and not sure it is in place. :-(

I still have a damaged USB controller and now with two problems not just one.

Is there anyone who can help in any way to restore my organ back to its 3 keyboard layout?