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Try this:
1) Use a 2.5mm I/O cable to connect its linkport to another calculator
2) On the working calculator, perform the following commands:
Code:
1337->A
GetCalc(A
A

3) If A is not equal to 1337, the "broken" calculator just needs a coarse-grained LCD cable replacement, as shown in my several posts in this topic.
KermMartian wrote:
Try this:
1) Use a 2.5mm I/O cable to connect its linkport to another calculator
2) On the working calculator, perform the following commands:
Code:
1337->A
GetCalc(A
A

3) If A is not equal to 1337, the "broken" calculator just needs a coarse-grained LCD cable replacement, as shown in my several posts in this topic.


Darn, it does return 1337....
I recently purchased a third purple TI-83 Plus for my collection, one described to have the jumbled/garbled LCD symptoms. Sure enough, I was able to power it on for a second and see the classic symptoms of course-grained ribbon cable failure. I replaced most the cable in two stages; my first, conservative pass didn't replace enough of the failed conductors. I also used isopropyl alcohol to clean a tiny amount of white corrosion off of the mainboard. I put the calculator together, and voila, another working TI-83 Plus in my collection.

After finally finding a ROM V2.00 TI-81, I discovered it exhibited coarse ribbon cable failure. Like the TI-83 Plus, it uses the same T6A04 display driver and thus exhibits a similar failure mode. I only needed to replace two lines; both were completely disconnected. As per usual, click to enlarge.



The calculator in question. Text rows 3 and 4 never really changed, besides for intermittent connection that changed the garbage there.


I hear you like PCB pictures. This was taken after messing around with the ribbon cable enough to view the ROM version, but not so much as to fix the calculator.


Repaired!


The calculator now operates normally. Clearly this was before I put it back together Razz. I also moved the foam back to its original position and cleaned the adhesive off the viewable screen area.
Nice work, CVSoft! I'm glad that the TI-81 can be fixed the same way as the TI-83+ calculators, and your soldering has clearly improved over the years.
KermMartian wrote:
I'm glad that the TI-81 can be fixed the same way as the TI-83+ calculators

Keep in mind that the ROM 1.x TI-81s use an entirely different display system (about the same as the TI-85/86, memory-mapped), so I have no idea how they respond to faulty ribbon cables. I haven't come across any with cable failure, but I think at least one Cemetechian had a TI-86 with cable failure (or had otherwise observed it).

KermMartian wrote:
years

Huh, it's been a while then Smile . I got a lot of practice assembling Arduino things, and the wider pitch of Arduino-y things was like a training ground for calculator ribbon cables. I'd also like to say that UT2004 improved my hand stability, but I can't be sure Razz. I'm confident enough in my abilities to start repairing calculators and reselling them, it'll fund buying cool calculators in the future.
Because I need a good place to put it: sometimes fixing the LCD isn't enough to repair an ailing calculator. In some cases, the fuse on the PCB needs to be replaced, and a proper repair involves replacing it with another fuse (rather than the lazy solder blob). For the TI-83 Plus and TI-84 Plus family calculators, the replacement fuse is the "0451.500MRL":
http://www.digikey.com/product-detail/en/0451.500MRL/F2574CT-ND/813052
I just fixed my friends ti-83+ using this tutorial and I found that even after the repair I could get screen errors if I pushed the graphing buttons too hard. I used an old 28 gauge IDE cable as my source of wire which is thicker than the cable Kerm used. (I think) I fixed this problem by grinding down one of the plastic supports in the calculator's back plate and the errors have not reappeared. Not really sure why this happened but if anybody else has a similar problem you know what to do. Wink
Thanks for sharing that experience, NikitaT! I've never heard of pressure causing the coarse-grained ribbon cable to intermittently fail, but I certainly believe that it's possible, and I hope your suggestion will help others who run into the same problem.
KermMartian wrote:
I've never heard of pressure causing the coarse-grained ribbon cable to intermittently fail

Kerm, it sounds more like the height of the soldered connections post-repair was at fault. A poor connection coupled with physical contact with the housing / deformation of the PCB would definitely cause issues. Since the wire was thicker and probably had thicker insulation, the possibility of reaching the housing's supports is more likely than with our 30-gauge wire. I don't believe that any of the plastic supports reach the PCB itself, but I don't have very much experience with Plus models Smile .
My own work, on a TI-83+SE:


I used what somone suggested, an old FDD/IDE cable, works beautifully, even stranded. For reference, here is a picture of the motherboard and a picture of the FDD cable:



The repair went well, here is a picture of it looking garbled:

And it looking normal:
CVSoft wrote:
Kerm, it sounds more like the height of the soldered connections post-repair was at fault. A poor connection coupled with physical contact with the housing / deformation of the PCB would definitely cause issues...

I think you are probably right, any issues this could cause over time and/or anything I could do to fix it? (Aside from grinding down one of the supports)
So, I have a TI-83 Plus SE (not the same one I've been posting about in my topic) with these issues, so I'm going to attempt this on Monday. I was wondering, how would I go about removing the original ribbon cable? Also, what is the best and/or most effective way to keep the contacts from accidentally touching or getting stuck together?
Spenceboy98 wrote:
So, I have a TI-83 Plus SE (not the same one I've been posting about in my topic) with these issues, so I'm going to attempt this on Monday. I was wondering, how would I go about removing the original ribbon cable?
I usually do not. I use an Xacto knife (or just the tip of my multimeter probes, because I'm measuring resistance anyway) to gently scratch off the ribbon cable material over the PCB contact, leaving the PCB contact clean and clear for soldering.
Quote:
Also, what is the best and/or most effective way to keep the contacts from accidentally touching or getting stuck together?
(1) Use rosin core solder!
(2) Pre-tin the pads on the PCBs that you're going to solder
(3) Clean your soldering iron tip frequently
(4) Use as small a tip as possible
(5) Use small-gauge wire (30 AWG is ideal)
KermMartian wrote:
Spenceboy98 wrote:
So, I have a TI-83 Plus SE (not the same one I've been posting about in my topic) with these issues, so I'm going to attempt this on Monday. I was wondering, how would I go about removing the original ribbon cable?
I usually do not. I use an Xacto knife (or just the tip of my multimeter probes, because I'm measuring resistance anyway) to gently scratch off the ribbon cable material over the PCB contact, leaving the PCB contact clean and clear for soldering.
Quote:
Also, what is the best and/or most effective way to keep the contacts from accidentally touching or getting stuck together?
(1) Use rosin core solder!
(2) Pre-tin the pads on the PCBs that you're going to solder
(3) Clean your soldering iron tip frequently
(4) Use as small a tip as possible
(5) Use small-gauge wire (30 AWG is ideal)


So, I can just leave the ribbon on? How do I pre-tin the pads? I'm pretty sure that that's the kind of solder my dad has, and I did order 30 AWG wire.
Yep, you can just leave the ribbon cable. I usually measure the resistance across each conductor, and only replace the ones that are >10-15 ohms. Often I later have to go back and replace the ones I skipped, though, so you may choose to replace all of the conductors. To pre-tin, hold the iron on the pad, touch the solder to the pad to melt a tiny bit onto it, remove the solder wire, remove the iron. Make sure you're hearing the pad rather than the solder. And of course, try to use as little heat as possible.
Just for some some soldering suggestions I find it almost easier to add solder to my iron and bring it to the pad for the case of tinning. It is bad practice else where though. That being said. It is better to just replace the whole cable. The rest will fail in time.
It was a success! It took a couple of failed attempts, though.


I don't have any pics of my soldering job because I didn't think that it would work, but now that it does, I don't want to chance messing up any of the wires.
Congratulations; glad that you were able to get it to work! What failed the first few times? Blobs of solder bridging pads? Broken wires? Some other problem?
KermMartian wrote:
Congratulations; glad that you were able to get it to work! What failed the first few times? Blobs of solder bridging pads? Broken wires? Some other problem?


Wires kept breaking, and there was some solder that bridged the pads. The only real issue I had was that one of the pads came off and got lost and I had to use a needle to pick out the copper wire and directly soldered to it. But now it works fine. Razz
  
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