Vintage CASIO Math Pet MP-500 teardown

I have this vintage device from CASIO which was actually a gift from Dad when I was in second grade or so. This is aptly named Math Pet - it helps you learn Math Tables and gives you simple arithmetic problems to solve. It also has a clock and a stopwatch.

I guess this product was released by CASIO after 1995 and it apparently it didn’t sell much? I scoured the entire CASIO website looking for the product’s info or the service manual. I could not find a single thing. I could not find anything much on the internet too. There were only 2-3 websites offering images of the device along with how to use it.

There was just one video on YouTube and that too just explaining its features.🤷

[youtube &w=1366&h=768]

I then asked the Reddit community for help. That too didn’t give any leads.

With no hope of finding a reference manual, I decided to open it up and see.

The problem:

The LCD display isn’t clear and has poor viewing angles
The slider switch stopped working

The not so clear LCD

https://www.reddit.com/r/AskElectronics/comments/dq7xmm/how\_can\_i\_fix\_the\_lcd\_of\_this\_very\_old\_math/

https://www.reddit.com/r/AskElectronics/comments/dq7xmm/how\_can\_i\_fix\_the\_lcd\_of\_this\_very\_old\_math/f618vez?utm\_source=share&utm\_medium=web2x

https://www.reddit.com/r/AskElectronics/comments/dq7xmm/how\_can\_i\_fix\_the\_lcd\_of\_this\_very\_old\_math/f681229?utm\_source=share&utm\_medium=web2x

Since people were suggesting to try and clean the device and connections. I opened it up.

Looks pretty neat on the inside

Looks like a well designed device with few discrete components

Ouch CASIO has dismembered the IC

No wonder I couldn’t find a reference manual. It’s irreparable, components can only be replaced. Plus it’s almost useless in trying to reverse engineer the IC with a logic analyzer to try and guess the IC used with these many number of pins. :(

If you look carefully you can see a dead ant inside (near the display filters). And how did it get there - I don

The sheet that

The slider switch is simply a piece of conductor

I did a bit of cleaning. Reassembled the whole thing back again. The screen looked better. The slider switch hasn’t improved much.

Update: The display went back to how it was initially in just a couple of days. 😐 So it’s more of a connection problem. I didn’t have any IPA (iso-propyl alcohol) to clean things thoroughly. So I just ordered some. Will have to do round 2 once it arrives.

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