Repairing Scientific Calculator Casio fx -991MS

[iori3310]

Hello.

I am posting with a new issue again. Hoping to get some clear solution regarding the replacement / repairing of the Casio fx - 991MS scientific calculator.

Here's the story -

A while ago my calculator stopped showing some digits on one side of the LCD panel and some blurry digits on the other side. After searching on the internet and watching Youtube videos, I got the idea of heating the ribbon placed on the top of the PCB. I tried to do the same but with a soldering iron. This made the ribbon melt on some point. This melting had stopped showing the digits on the LCD screen completely.

Now, at this point I disassembled the LCD display and feeling confused whether or not it can be fixed / replaced / repaired. The real anxiety is that the calculator still works and powers up properly but due to no LCD display, it is now totally useless.

If anyone knows anything regarding this issue, that I can fix it or replace it. Please provide me with proper suggestion or instructions.

Thanks in advanced.
Iori

 

[JimB]

A while ago my calculator stopped showing some digits on one side of the LCD panel and some blurry digits on the other side.

Which probably indicates that the LCD panel itself is faulty.

This made the ribbon melt on some point. This melting had stopped showing the digits on the LCD screen completely.

Yes, the drive to the screen is unlikely to be able to jump across the 5mm air gap.

Please provide me with proper suggestion or instructions.

Well, you could try re-soldering all the connections to the ribbon cable and then see what is shown on the display.
But, given that the display itself is probably faulty, I suggest that you need a new calculator.

The real anxiety is that the calculator still works and powers up properly but due to no LCD display, it is now totally useless.

If you buy the same model of calculator as a replacement, and keep your old calculator safe somewhere, in five years(?) time when the new calculator fails, maybe it will be some other component which has failed and you will be able to make one working calculator from the parts of the two broken ones.

JimB

 

[iori3310]

It's like asking for someone to die, just to get their organs for donations. Anyway, thanks for your suggestion.

 

[KeepItSimpleStupid]

The usual way of attaching an LCD is a zebra strip. https://en.wikipedia.org/wiki/Elastomeric_connector

Usually cleaning and careful positioning restores it.

Not sure how your LCD is connected.

 

[throbscottle]

You can see it's actually a soldered ribbon cable, or rather a mostly un-soldered ribbon connector. I've seen soldering iron bits for exactly this type of thing - they have silicone insert:
**broken link removed**
It even mentions repairing calculator on the page.

This one tells you how to use it: https://console5.com/store/soldering-iron-t-tip-for-lcd-repair-40w-5mm-tip-size-version.html