Case closed: it was the foam, my GB got the light back! Thank you very much for your concern, and of course, very special thanks to EGR!!!!!
These forums rock!!!!!!

Samwave, there's nothing at the PCB that indicates that there should be any contact for that brown ribbon.
kitsch, as you say, it's just an outright dead panel, so it looks like a contact issue. I didn't force neither the membrane nor the circuit board, I just used a specific cleaning product for electronic boards and I waited till everything was completelly dry. I do hear the whine you say when I turn the switch to light mode, so that seems to work. As I said, hope it's the foam! I'll let you know.

Thanks to all of you guys, I really appreciate your help!!!!!

No, I don't have any foam pad under the EL contacts, and I didn't notice that any piece slipped away when I opened it. But now that you pointed that, it's crystal clear that I misssed it!!! So I'll have to replace it. As soon as I get one and try it, I'lllet you know if it worked. Thank you so much!!!!

there is a little pad that sits right under this for some pressure, but it looks like its under there.  if not, egr found your problem probably!

try cleaning the contact pads for the EL panel too.  if the button contacts in this unit were so dirty they didn't work right, most likely some of that gunk got into this area too.  clean both the EL contacts and the ones on the PCB, because if you leave one dirty and clean only one you'll just transfer dirt to your clean surface.  like how when people put new edge connectors in a NES then ruin them by inserting terribly dirty and gunked up NES carts. 

if the leads in the EL panel just came loose from the membrane which illuminates, you'll probably get some flickering instead of it staying off (and you can generally 'fix' this with some pressure to encourage them to sit on the membrane again).  if its just an outright dead panel, i'd say its a contact issue or else the leads in the EL panel were severed somehow.  which shouldn't happen unless you were pretty rough with it, its a good quality part.

well anything could be the problem i guess.  like cleaning liquids into the EL circuitry which shorted something out, etc...  its probably with the EL panel though, they can be a little finicky sometimes. 

when you turn the switch to have the light come on, does the console have any high pitched electric whine sound added?  you can hear the EL circuitry in a light from the outside if you know what to listen for.

It has been a very long time since I've modded; but where is the PCB? I see the brown ribbon cable and I swear there was more to it than a brown cable/thing.

Never installed an EL backlight so I could be completely wrong. haha

If I remember correctly, there should be another foam pad (like the red/orange one's in your pics) that keeps the EL contacts pressed against the circuit board.  I can't tell from these pics if you have that?

Hi everyone!! I just found this site and I'd like to ask for help with my GB light:

I recently opened the GB in order to clean buttons & rubbers, since some of them were working really bad. It went well, now all of them work great, but the light doesn't work!! Now, there's no difference between "on" and "light" mode.

  I assume that, in my ignorance, I didn't realize how to connect the EL light back when I opened the GB; Can anyone please tell me how to do it?

Or maybe did I break something and there's no way back? I'm posting a couple of pictures:

Thank you very much!!!!