Imagine that a line of pixels fails as I post this


Degradation of the fine ribbon cable in older TI graphing calculators is a familiar problem, manifesting as missing rows and columns in the LCD. Otherwise perfectly functional calculators are put to waste over two relatively short-lived ribbon cables, one of which is unreplaceable, with long-term repair methods elusive.

As the LCD is integral to the very purpose of the calculator, I was interested in correcting this common issue for the sake of correcting it. Something as trivial as "exercising" missing lines in the display would often reinvigorate them for about a day, which prompted me to investigate a more reliable repair.

Though TI does not specify the assembly method actually used, many similar ribbon cables are applied by hot press. While this entails expensive, specialized equipment, I learned to imitate the hot press process using inexpensive, readily-available components through a video on automobile instrument panel repair. Note that I modified the method since we are not able to install a new cable.

I have applied the method to seven graphing calculators exhibiting fine ribbon cable failure. In the 20 days between the repair and this writing, I observed a high degree of success across the calculators repaired.

Before continuing, check whether the fine ribbon cable is culprit. Missing or intermittently functioning lines are prime indicators of fine ribbon cable degradation. If the contents of the screen are garbled or corrupted, the coarse ribbon cable will need to be repaired first:


Get a T-tip with silicone insert like this:

These are available on eBay for about US $7. The point of this is to distribute heat and pressure along the ribbon cable connection in a similar manner to a hot press. If given a choice between a tip for 30W, 45W, 60W, etc. choose 30W unless using a larger unregulated iron.

Use a soldering iron that fits this tip, which generally goes down a shaft without screw threads and is secured by a screw on the side. An iron with temperature control is preferable, though I have found that a 30 watt unregulated iron will do, if you are skilled or inclined to use one.


Install the T-tip with the silicone pad trimmed to size and allow the silicone contact surface to reach around 150 C. The 30W unregulated iron I tested reached this temperature as well.

Remove the circuit board from the calculator. Locate where the fine ribbon cable connects to the edge of the LCD glass. If there is foam padding attached, gently peel it off and set it aside. Be sure NOT to tear the ribbon cable off either end, which will ruin the chances of a successful repair.

Locate where the fine ribbon cable connects to the board. Set the LCD face down on a flat, non-abrasive surface and place the iron flat on the connection as such:

Use firm, even pressure on the connection and slowly slide the iron across the width of the cable. Take ~20-25 seconds for one pass. Do another pass. Alternate to the glass side and place the iron flat on the glass/cable connection as such:

Make two passes across the connection as before. The edge of the LCD may change color as heat is applied, but if it is turning a dark or purplish blue, move the iron faster to prevent overheating.

Now reassemble the calculator and test if the display looks good. If any defects remain, do another pass over the cable connections. There is the possibility, however, that some lines do not resolve even on the second or third attempts. These, unfortunately, will remain unrepairable.

Once everything looks good, put the foam padding back where it was, if any, and fully reassemble the calculator. The repair is complete.

Note: From my testing, the silicone pad is necessary to distribute heat and pressure along the cable. It will also wear out when used multiple times. Replace it when it no longer slides smoothly over the ribbon cable connection.

Note for TI-85/86 repairs:
The TI-85 and 86 feature two ribbon cables, one on top responsible for vertical columns and one on the side for horizontal rows. Determine which one needs repair and move the side ribbon cable out of the way if necessary. I have yet to attempt a repair on the side ribbon cable, which appears more challenging to access than the top cable.

Results and Limitations

Of the seven calculators that I have repaired using this method, five exhibited severe ribbon cable degradation (>10 missing lines), including:
-2x TI-82
Nearly three weeks after the repair, three of the displays are fully functional. The TI-85 has served as my main calculator since the repair.

Below is the TI-80, before and after repair:

The TI-83 had two rows that would not resolve despite three repair attempts:

One TI-82 has one column that will start working once something is displayed on it. Despite two repair attempts, this column would not stay put when the calculator was powered off for a longer period of time.

Another two exhibited mild degradation (<10 missing lines):
After the repair, both calculators had fully functional displays throughout the 20-day period.


Ideally, an economical, readily-available replacement LCD assembly without such a flawed ribbon cable would be available to prolong the useful life of TI graphing calculators. This is currently in the works as we see with KermMartian's Surget. In the absence of a finished replacement LCD, this currently is the most effective method I have found to breathe new life into aging calculators, restoring the majority of, though not all, missing LCD lines.

Across a sample of seven calculators over 20 days, each LCD line that was repairable and repaired remained functional. The long-term viability of this repair method remains to be discovered, though it is one that vaguely emulates a common method of LCD ribbon cable assembly at the factory. In the meantime, I will take note of and post any significant changes that I notice on the calculators I have repaired using this method.

After five months, it is evident that repairs were not reliably persistent.

TI-80: Several missing columns and a missing row appeared. All but four columns returned to normal almost immediately. After moderate use of the screen, one column remained blank.
TI-81 (VSC rev. E): Three missing columns appeared. All columns returned to normal after moderate use.
TI-82: No change; in same condition as immediately after repairs.
TI-83: No change.
TI-85: (0396I): Three missing columns appeared. After moderate use of the screen, one column remained blank. (0197I): No change.

All calculators, except for the 0197I TI-85 (used daily), were largely unused in storage throughout the five-month period. I am not sure whether that made a significant difference.

No further repairs were attempted. Hopefully the repairs on the TI-82s and the TI-85 will continue to last a while more. I'd say this was a rather fun experiment and I will continue posting any significant developments.

And thus, reliable ribbon cable repair remains elusive for now.
Dang as this was a promising method - I still plan on getting one of those T tips however.
Booooooooooooooooooooooooo. Thanks for the followup and research!
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