Casio CD-401 Revive

     Since my recent obsession with calculator watches I took the endeavor of rebuilding nonfunctional ones. My last purchase was a mint Casio CFX-200 and paid around 250 USD, not cheap. You can find these in various conditions with different prices on ebay. Now that I had that one I wanted it's databank cousin the CD-401. I managed to buy one in good condition for 80 USD (including shipping form overseas) but it had an issue with some "dead pixels". Possible problems could have been damaged contat strips, faulty module, faulty display..etc. For the fix I purchased two other CD-401s  from Turkey.

     The watch with dead pixels, thanks Andrei - woodstok27 for the effort on shipping this overseas at a convenient rate and all the great communication. The overall condition of the watch is good with minimal wear even on the side buttons.

     Below are the two donor watches, they were sold as faulty with no indication of what part might be faulty so I gambled that I could find the right functioning parts inside.

                               

     I started by taking apart the one with the dead pixels, used a sharp knife to slide under it rather than a screwdriver, this way you do not risk damaging/scratching the case. The module is retained in place with a small clamp that is situated at the middle top of the module. Inserted a thin flat screwdriver between the module and the case and slowly aided it out. Once it is out you have to detach the shiny tin contact plate - this is the component that also embodies the button contacts and transmits the positive form the battery to the module. This is retained to the rest of the plastic module with clamps on all 4 sides. Once the clamps are unhooked the button contacts have to be fiddled with to take the whole thing out. After this is taken away there is a small plastic cover for the module that easily pops out. What is is left is the board, this comes out easily too, but care must be taken not to damage the microlight that is underneath on one of the edges. With the module out the LCD is easily accessible. I took the LCD out, took the rubber contact strips out and fitted the new LCD. Since I was with the module in hand I cleaned the entire PCB with isopropanol. I reassembled everything back together and all pixels now were working.

     I could have tried to clean the old LCD contact sides and try with that one but since the watch was very clean inside I assumed there were just dead pixels. I may try testing the old LCD in the future and see if I apply voltage to all segments if they light up, but for now I am happy with the results.
    Below is a shot of the CD-401 next to the CFX-200, looking good together.