I looked at one of the replacement screens that I also got, and the ribbon goes in between two halves of the metal enclosure for the LCD. If that simply holds the ribbon in place, it might be a very simple fix, just popping the screen apart, pulling out the old ribbon, and taping down the new one. If you have to solder it though, I probably don't have the means nor skill to do that and will try my hardest to not cry myself to sleep over the $3 I wasted on them.
Yeah, this is mainly what I was wondering: how does the ribbon connect to the LCD? I'm also not keen on soldering. And considering how badly I may or may not have treated my cable in my shell swap I'm not too keen on opening up the top again to investigate the connection to the LCD... at least, until I can rule out connection issues. If my ribbon cable is damaged after all, I'll take a look at it tonight.
BTW, I think it's cool that you're trying to fix them up for profit and I wish you luck on that. I considered it, more for fun than profit, but if I could turn a profit why the heck not, right? But after running some numbers I decided that it's kind of risky with very small profit margins and with the DS Lite being an older system the demand isn't super high (so there's risk of sitting on stock or an ebay listing not pulling in fair market value). I'll share with you my personal thoughts and findings.
My assumptions were $20-30 for a broken system off ebay (the ones that work but have a broken hinge go for more than ones with power issues or cracked lcds, of course) (also most don't come with power chargers, some are missing styluses, etc.), and, disappointly, anywhere from $45 to $70 for a used DS Lite. So if you assume buying and selling at those rates, once you factor in parts, you might be able to eke out a profit margin but only if you order all your parts in bulk from China and use them all up perfectly and so on.
Buying systems that are fully functional with broken hinges is the least risky purchase you can make--the first broken DS Lite I purchased had a power issue that, as described, sounded like it was going to be a simple F1/F2 fuse fix. When I got the item I discovered that some sticky liquid substance (presumably juice) had leaked in through the GBA slot (there was some slight stickiness left there, and the water damage indicator on the board near that slot was activated) and fried the chip on the motherboard. It smelled burnt, and when you opened up the shell you could see scorch marks on the chip. Now it wasn't a total loss because the shell is in extremely good condition, I got a battery out of it if nothing else, and I actually think the LCDs and such are probably fine. But if you were considering re-selling this unit, you would have to put in, at the very least, a new motherboard, which is, cheapest I saw, $28, shipping included. For that price you can snag a working system with a hinge problem--which is exactly what I did--and use its motherboard and salvage the extra parts.
So on that note something I've noticed is, is that most of the time I think that salvaging parts and selling them would net you a much higher profit than a working system--assuming you could sell your stock and not be left sitting on a few parts. However, the market is pretty flooded with parts so there's that to consider...
Anyway I could ramble on and on about this because I found the whole thing quite fascinating, and I love cost-breakdown-analysis type stuff, but I don't want to bore you / get too far off topic from the original post.
On the other hand if you'd like to continue this discussion in a PM or something I'd be fine with that; I will share whatever I know freely because like I said, I wasn't actually that concerned with profit and I don't think I'll be pursuing this route for money. Similarly, I picked up a 3DS XL with a broken top LCD to tinker with so I could talk a little bit about the potential market and costs there, since I looked into that as well.
