I got a TI-83 Plus (S/N 2631068xxx S-0505F) to fix from a friend, noting that it had dark vertical lines on the home screen and that small text and menus had dark bars next to every character. I assumed some of the ROM got corrupted, so I upgraded it from 1.17 to 1.19 after dumping the ROM for analysis. The dumped ROM ran perfectly on WabbitEmu, and was a byte-for-byte match with another 1.17 calc. When I turned on the calc with 1.19, the "TI-83 Plus 1.19" was just a garbled, pixely mess and the calc turned off after I pressed [CLEAR]. It wouldn't turn back on until I pulled the battery and held [ON].

What might have caused this? I'm assuming it can't be repaired.

Images of the mainboard here.

This is textbook ribbon cable failure, and very fixable if you have a steady hand, a soldering iron, 30 AWG wire, and suitable wire clippers/strippers for such thin wire. I have fixed about a dozen or more calculators with the same symptoms. (To my slight stupidity) I posted up repair instructions here on Cemetech, hereabouts:

http://www.cemetech.net/news.php?id=418

Yep. This is the exact same problem I had here: http://cemete.ch/t6981

I have yet to repair it, sadly. I need to get a good soldering iron... the one we have is definitely not good for precision-requiring work. I also sort of forgot about it for a while...

I think I'll go to my friend's house tomorrow. His dad might be able to provide the required tools for repair. And now, I stop before I keep heading further off-topic.

No, this is quite on-topic. Feel free to share any experiences from your repair here or in your own topic; more information can only help other people be more successful with the repair, I would think!

Thanks guys, I'll do the repair soon. Technomonkey's example was very similar to mine. I'll go get some wire within the next few weeks and let you know if/how I fixed it.

A LCD ribbon cable is quite hard to repair. The battery leaked on my HP 200LX and destroyed the LCD ribbon cable, i had to take it to a old devices repair shop and cost me 150$ to fix it...

There's actually two ribbon cables inside of the calculator. The one connecting the display to the LCD board is not even worth trying to fix if it's torn or otherwise damaged if it's in a calculator. The 17-wire cable that connects the calculator's mainboard to the LCD board is a DIY fix.

That's exactly correct. Sadly, they combined the two for the TI-84+/SE calculator, so those are well-nigh impossible to fix. And forget a TI-89.

Hm, my friend's calculator is darker in the middle of the screen than on the sides... Could this be another form of ribbon cable failure?

That sounds like pressure damage. It's only any sort of ribbon cable failure if there are either garbled characters or a fully-black screen (the easier-to-repair cable) or missing/lighter/darker rows and/or columns (the impossible-to-repair cables).

Conveniently enough, I got another TI-83 Plus (2385012xxx S-0403D) today with the same problem. I heated the glue under the ribbon cable and pressed down on the connection area to reconnect it. It almost completely solved the problem, but there's still dark vertical lines in the small text. Is the ribbon cable itself damaged?

EDIT: Here's the pictures, along with a TiLP2 screenshot.

I'll check the resistances with an ohmmeter and post the results here.

Isolated rows and columns are failures in the finer-pitched ribbon cable's connections; garbling is the coarser ribbon cable. What did you use to re-heat/re-glue it? I have always found that method to be inadequate in the past.

I also found heat to be inadequate on smaller connectors, but it was worth a shot and it almost worked.

What is strange is the screenshot TiLP gave me. Does the calculator get the screen contents from its own memory, or does it ask the screen controller for it (past the coarse ribbon)? Both were taken near the same time.

They ask the screen controller for it, so you're seeing double corruption there. I always find it fascinating that you can tell the difference between damage in the first and secondary ribbon cables by whether a screenshot shows an uncorrupted screen or not.

Oh good, I thought it was just copying some screen buffer in RAM and sending that, and that the OS was corrupted. I find it interesting how the screen fonts garble the way they do when there's a poor ribbon connection. Come to think of it, I've never tried taking a screenshot of the calculator in its initial state, considering double corruption takes effect.

I think you may have overlooked my question about your heating method, as I'd like to give it another shot on the fine-pitched ribbon cables of some stubborn TI-86 calculators. What's your heat source, a hair dryer, a heat-shrink heat gun, something else?

Well, I must have. I used a hair dryer set to max heat (over 160F, don't know how hot). I'll also try it on the same friend's TI-92 that's missing a few lines.

If this works, it will allow me to save even more calculators than my current soldering method works on. I'll keep you posted.

I applied pressure to the cables at where they attached to the mainboard with the multimeter probe's tip. The LCD board wasn't affected. All resistances are now less than ~50 ohms. The screen is askew in the picture because I'm just holding the bottom of the calculator together for testing.
One calc down, one to go...

I wouldn't recommend this for the finer cable as it will probably damage the cable; just use heat and light[er] pressure.

Just as I expected, one of the connections I made failed this morning. I'll retry it using heat in combination with pressure. If that fails, I'll solder a new wire.