TI-66 display issue

[jebem]

(08-20-2019 02:57 PM)CarlGundel Wrote:  

(08-16-2019 06:03 PM)CarlGundel Wrote:  I will take your advice and have a look inside to see if there is any corrosion.

Seems completely spotless inside. No battery leaking ever as near as I can see. I will still try to clean the display contacts.

-Carl

Well, a fresh battery as you initially suggested is worth the try, despite a weak battery should not result in such strange behavior.

Assuming that the battery is good, I see three common causes for strange behaviors:
1. Battery electrolytes leaked over the mainboard;
2. Electrical conductive liquids (like coca-cola or similar) dropped over the keyboard may have found their way to the mainboard;
3. Faulty SoC (System on a Chip processor.

We can fix causes #1 and #2, by fully dismantling the machine and cleaning it all (except the LCD assembly) with warm water and dish hand wash detergent, and before it drys, use IPA (isopropilic alcool) on the mainboard to remove the water and remaining residues, then let it dry under warm room temperature for one day. The LCD can be cleaned with IPA alone.

As for cause #3, a new SoC chip would be required and as far as I know can only the found on a donor machine these days.

While battery leaking is not common on coin cells, it may indeed leak and I found quite a few calculators with corroded and short circuit PCB traces by the battery electrolytes.