Sam wrote:
Recently, Iíve gotten into the business of buying bulk orders of TI graphing calcs on Ebay listed for parts of repair, mostly because Iíve started getting into the collection and documentation of old hardware revisions. Iíve found that, in most cases, screen issues caused by both ribbon cables can be fixed by nothing more than a soldering iron. For the 17-contact ribbon cable, I set my soldering iron to the lowest temperature (150C) and press firmly on the glue on each of the contacts in 2-3 places per contact using the tip of the soldering iron for about 2 seconds. For the LCD cable, I press firmly on the ribbon cable contact strip with the iron while slowly dragging the iron across the cable (with the plastic sheath still on the cable). Though this isnít the best way to do it, it has succeeded in fixing every TI-83 I have attempted to fix, except in a couple cases where the ribbon cable was partially severed and I had to solder my own connections. I measure the resistance of the connections before I put the calc together, and redo connections with resistances above about 8 Ohms.

The 83+ and earlier calcs are significantly easier to work on than the 84 and later. On some calcs, like my 84 Pocket SE, dead lines may be caused by connections between the LCD panel and ribbon cable that are inaccessible because they are physically beneath the LCD. I have yet to figure out how to fix calcs with this issue, as I do not know how to separate the LCD from the PCB beneath it without breaking the fragile glass.


This method helps for several weeks, maximum for several months. The display rarely recovers 100%.
Nik wrote:
I am not sure if anyone has ever tried that, but I want to see if a failed fine ribbon cable can be replaced with fine enameled wires that were pre-arranged such that they rigidly remain correctly spaced apart. For example, by placing them on adhesive tape, hot glue or the like. This could allow them to be soldered somewhat similarly to a regular SMD package with small pin pitch.

If anyone has a calculator with a failed fine ribbon cable and is willing to ship it to Germany, I would really like to try this - but as a word of caution, I cannot guarantee that whatever I do will not destroy the calculator.


The display size is about 75mm horizontally. On this 75mm there are 64-row tracks and 120 columns. 184 tracks. I don't think you can replace them with thin wires at home. And the type is even narrower, on it the step of the tracks is even tighter.
Edit: This was my approach to a coarse ribbon cable repair, though I missed the point of the question being about the fine ribbon cable
Pi Time wrote:
Nik wrote:
I am not sure if anyone has ever tried that, but I want to see if a failed fine ribbon cable can be replaced with fine enameled wires that were pre-arranged such that they rigidly remain correctly spaced apart. For example, by placing them on adhesive tape, hot glue or the like. This could allow them to be soldered somewhat similarly to a regular SMD package with small pin pitch.

While I don't have a broken calculator to spare, I repaired my 83+SE in similar fashion. In the absence of sufficiently thin or enameled wire, I sandwiched single copper strands between kapton tape to make a "ribbon cable". Not the neatest, but got the job done.

I scanned and traced the failed ribbon as a guide to assemble the ribbon cable. Tape sticky side up over the pattern, aligned copper strands to the pattern, sealed it in with a second piece of tape, trimmed excess wire and tape. Of course, proper enameled wire would still be superior.


Sam wrote:
I'd like some sort of very blunt iron that can cover a much larger flat area than a soldering iron, to hopefully reseat the whole cable's glue as though it was factory.

Comically large iron head I tried out. I had no luck with it, but it could also be a lack of pressure or the cheap soldering iron I was using.
Pi Time wrote:
Sam wrote:
I'd like some sort of very blunt iron that can cover a much larger flat area than a soldering iron, to hopefully reseat the whole cable's glue as though it was factory.

Comically large iron head I tried out. I had no luck with it, but it could also be a lack of pressure or the cheap soldering iron I was using.


I finally got an adjustable iron and apparently, the large iron head does help. I do not yet know how my iron measures temperature, but 150C at the contact area is desirable (I used the temperature multimeter to read) I managed to fix all the missing columns on my TI-85, slowly (one pass in 25 seconds) sliding the iron over the ribbon cable, both at the PCB and glass connectors. How long this may last, I am not sure.

Thanks Sam for the 150C temperature suggestion!
The display I ordered has finally arrived. Now I can experiment with connecting it. ST7567 display controller, SPI connection interface.
  
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