DVD player start-up failure

Hello there.I have these 2 faulty dvd players that I can't fix.Both of them always fail on start-up and eject the tray even though tray switch is fully on in CLOSE position.All 3 motors and 2 switches are ok.So I think the fault is on the decoder board.For the second one,I swapped the +12/-12V pins to cure the problem,but to no avail.Instead,before I could remove the power connector,there was some smoke coming off the board.I thought I had a good idea seeing that some markings on that board were wrong.Now I would like you guys to help me repair these 2 boards.Both are chinese made.I hope you can tell which brand(s) chinese dvd players are usually clone of.So I try getting the service manuals.Or at least,I will be content with any circuit diagrams of the original brand(s) or for chinese clones.
Thank you all in advance for your answers,
Etonam.

My sister's DVD player developed a similar problem, shutting down a few seconds after its power-up cycle.

I tried disconnecting power for over 20 minutes. (Letting all circuits fall to zero, which helps solve many equipment problems.) The problem remained.

I did not swap the power supplies. I suspected it would create more damage.

So I decided the dvd player must be 'brain dead'. It happens to some appliances after years of use. It went to the recycling center.

I suspect you did not lose much by causing smoke to come from your dvd player. It was probably unfixable. You would need a detailed schematic, and sophisticated instruments, to troubleshoot it. Even if you found which IC is faulty, it is unknown whether you could obtain a replacement.