Electronic calculator repair

[jimbo84]

I have an old calculator, it’s been in a drawer for donkeys years and the two button cells have leaked all over the bottom of the PCB doing some damage.

Cleaned it up with iso alcohol and put in new batteries but it still didn’t work.

Traced a couple of hairline splits on the tracks on the PCB that I blobbed with solder to repair.



It now works but the display is not correct
This should be a zero



And these should be all the number 8


Being common to the whole display is it likely to be another bad/broken track or is the LCD toast?

PCB for interest.


No purpose to repair other than my own interest.

 

[Seadog]

It's the same two segments in each digit.
If it uses a "Zebra strip" to connect to the display, then it's quite likely to be oxidation of the pads on the pcb.

 

[jimbo84]

It's the same two segments in each digit.
If it uses a "Zebra strip" to connect to the display, then it's quite likely to be oxidation of the pads on the pcb.

Thanks, I'll take a look at that and see if it can be cleaned up.

 

[Maker]

My money's on the zebra strip too.

 

[jimbo84]

Had a look at the LCD ribbon and one edge wasn’t making a good contact having become detached.



Ran over it with the soldering iron a couple of times and it seemed more solidly connected. Powered up and I had a good display.



Hadn’t realised the C and AC buttons weren’t working either, traced to a hairline split in a track. Soldered that too and it’s fully working now.

 

[Misterg]

Excellent.

You must now perform the official calculator test:

Enter 58008.
Turn the calculator upside down and take a picture of the display.
Post it here for expert verification.

 

[Windy Miller]

I love those old Casio calculators.

Here’s mine that I used at college back in the late 70’s

 

[JohnH]

Mine.

 

[Pigeon_Droppings2]

This is my daily driver...still works faultlessly and the hard case has kept it in great condition.

At school I had the fx450....dunno what happened to it.

 

[Morris]

My old college calculator.

 

[Mikey D]

I find an abacus more than adequate

 

[Bornfree]

Casio stuff is brilliant. I found an old casio lcd watch that I broke the strap around 25 years ago and it's still working.