TI-83+ Display - Line of Pixels Missing - Ribbon Cable Contacts?

[salil]

I have TI-83+ graphing calculator hanging around from high school and a row of pixels appears to be "missing" (it's been like this for years).  I'm guessing some of the tiny contacts of the black ribbon cable aren't making proper contact...does anyone know what might be the issue?  I was a little hesitant in my initial trial using heat gun as I'm not sure if this is the issue and it all seems to be very delicate.  Can anyone confirm or advise before I ruin this graphing calculator?   

[bktemp]

This is a common problem on older lcd screens: The cable is glued to the display glass using a conductive hot glue. It is possible to repair the contacts but the success is limited without special equipment. You need to heat up the area and apply pressure. Then cool down keeping the pressure. Therefore heating with a heat gun does not help because there is no pressure on the contacts forcing them together.
I have repaired severel displays using a soldering iron set to the lowest temperature (around 150°C).

[mojoe]

Rather than fooling around with glued connections, I removed the old flex cable and replaced it with regular ribbon cable. I soldered each connection on the LCD and the main board. This makes it a permanent fix and I don't have to worry about the glued flex coming off again. I repaired dozens of TI calculators this way.

[salil]

I checked the continuity between the connections on the two boards that the glued FFC connects and it seems to be fine so I guess that FFC is not the issue...?

[bktemp]

This cable is fine. The problem is the cable directly at the LCD glass.

[smjcuk]

I'd see if you can find a functional one with external damage or pen marked (unsurprisingly common with students). They go for not much cash and you can do a brain transplant fairly easily. Once the LCD goes on these they are nothing but trouble.

I buy and sell TI83/84s quite often. Its quite lucrative as there is a yearly cycle of sales and purchases as people leave and enter education respectively.

[Grapsus]

This cable is fine. The problem is the cable directly at the LCD glass.

Yep, missing lines or columns is necessarily a problem between the LCD driver chip and the glass panel. If the lower ribbon cable was damaged, all characters on screen would have deformations.

I'd see if you can find a functional one with external damage or pen marked (unsurprisingly common with students). They go for not much cash and you can do a brain transplant fairly easily. Once the LCD goes on these they are nothing but trouble.

I buy and sell TI83/84s quite often. Its quite lucrative as there is a yearly cycle of sales and purchases as people leave and enter education respectively.

It's not that simple. There have been five or six different versions of the TI-83+, they all have minor variations on the display module. Some are 3.3V and other 5V. Some of them have the LCD controller circuitry on the main board and other have the same circuitry on the display module. There is a lot of info about that on datamath.org

I love using TI graphic calculators, I have several, but the quality of those LCD displays is just pure shit. They're selling them for around 100$, for a z80 CPU with an LCD, and still every new version does something to cut down the costs. The very first TI-83+ I owned as a kid developed the same problem where a line was missing. I tried heating the glass connection but looking very closely I found that the transparent ITO track on the glass for the missing line was simply cut just before arriving at the ribbon cable. I guess it was barely making contact, until one day it stopped conducting at all.

You could try to find a broken TI-83 and transplant the screen. But really it's not worth it. 90% of broken calculators you'll see will have LCD problems too. And even if you find one, you'll still have to pay something like 5 or 10$ for it. I don't know if it's the case everywhere, but here I can often buy used TI-83 for like 15 euros.

[smjcuk]

Used TI's go for a lot of money here in the UK due to the strange dependency on them in education and the artificially high price. Depends on the time of year but late summer they can fetch £50-60. Outside that you can grab them for £20 or so and a knackered one for £5-10 which has good plastics. I tend to buy a few (10 or so) from students leaving school at the start of summer for virtually nothing and then ebay them after that. Made £1500 in 2009 at the peak sales. I had 40 of them in stock at once as well

There are only two major hardware revisions: 83, 83+ with various board and ROM revisions that you see here and both are made by Inventec and the part supports are the same so it's pretty easy to transplant bits.

I don't transplant the display only - everything other than the plastics gets moved over. So display board, motherboard, the lot.

Agree that they are horrible and unreliable calculators though. I mean shifted exponent key - c'mon TI sort your shit out.

I use a Casio.

[Grapsus]

Haha maybe I should buy a few tens when the school year ends and sell them in august on UK ebay ?

I would never use a casio. TI calculator hardware is a shame in terms of reliability, but I absolutely love the firmware.

My favorite is the TI-86. It is not well-known, it has the same CPU as the TI-83, but a larger LCD, with more characters, exponent is not shifted and it has native support for binary and hex :DD

[smjcuk]

Haha maybe I should buy a few tens when the school year ends and sell them in august on UK ebay ?

I would never use a casio. TI calculator hardware is a shame in terms of reliability, but I absolutely love the firmware.

My favorite is the TI-86. It is not well-known, it has the same CPU as the TI-83, but a larger LCD, with more characters, exponent is not shifted and it has native support for binary and hex :DD

It's easy money. I've given up on that last year so I won't post you dog crap if you flood the market

I rather like the TI-85/86 as well but you just can't get one here that isn't broken or yellow from nicotine. Same with musical instruments

[m100]

Got the same problem with a TI68, it's still just about usable.  I was wondering about fixing it by using a plastic bag sealer to remelt the glue from the ribbon to the LCD. 

[EdFab]

Rather than start a new thread, I thought it would be better to resurrect this one since I have the same exact issue that the original op had. I've got a TI-83 Plus with a single line of pixels missing, and that is the only problem. What I gather from the the posts here is that the problem is with the cable physically connected to the lcd. I took the calculator apart and exposed a portion of the cable close to the lcd itself. I've attached a photo showing the area. To try the soldering iron remedy, where would I apply it? All along the area that I've exposed? Other than the dirt, I don't see any obvious signs of problems with the cable.