I just got in two TI-83 Plus calculators from eBay with screen issues. They had blue and purple polycarbonate cases. These seemed somewhat rare so I figured, worst case, I'd transfer another calculator into the colored shells. But I'm handy with a soldering iron so figured I would try my hand at repairing or replacing the ribbon cables.
I was looking into repairing a friend's GameBoy and saw this video: https://www.youtube.com/watch?v=-Cj5Pzuz06M
. Long story short, he uses a soldering iron to attempt to re-bond the ribbons.
After disassembling my TI-83s and cleaning all of the display contacts with 91% isopropanol (can't discredit someone spilling something on the calculator), I took my Weller WES51 soldering iron with a PES51 pencil and a wide tip, set it to 375 F, and applied gentle pressure to the back side of the ribbon and PCB. I spent about 4 seconds on each individual pin, then, worked back and forth across the whole ribbon.
While I was doing that, the calculator shells, buttons, and silicone domes took a bath in my cheap Chinese ultrasonic cleaner, in reverse-osmosis water with a denture tab or two. I rinse with tap water and do a final rinse with distilled water to prevent spotting, then dry thoroughly with microfiber towels and a fan. I gave the screen a wipe with isopropanol and a finishing wipe with the micro fiber cloth.
After this, both calculators looked and worked like new. Success! I'll try my hand at others in the future - maybe a TI-68? (Not a typo, 68, not 86.)