Casio C-701 Fix attempt

   So I got a Casio C-701 on eBay in badly bused condition, I attached an image for you to see, window cracked, buttons missing, dirty, etc.

                       

   But I was hoping to find some decent parts inside, maybe even get it to work. After receiving it first I removed the module and disassembled the case (and I mean removed side pushers, keyboard crystal, etc). I managed to salvage and clean everything but the crystal and keyboard.

   Regarding the module I disassembled it and started to do a full diagnose. At first glance there was a lot of corrosion due to leaking batteries so I had to clean that up. What I was pleased with is that all the other parts on the module except the PCB were quite clean. After the PCB cleanup I started to check with a multimeter the traces that looked suspicious. Needless to say I found three in close proximity to the batteries that were broken. Usually it happens in this area as it is the most exposed to corrosion. 

   For the repair of the traces they had to be regenerated. Usually this can be done in severa ways (make bridges with wires, retrace them with a fine soldering iron, regenerate them with conductive silver). But I support the last solution, the first two could be clumsy on small traces and adding wires just adds thickness to the module and that usually leads to bad contacts when reassembling the watch as the parts do not come together properly. But regeneration o the traces requires a lot of work if you want to be neat and have a good result in the end. I recommend doing it only after you know exactly what to fix and that it will work after the fix.So just to see if only the traces are the fault I had to do a quick rewire. Below are some shots of the work done under the microscope.

    Needless to say after reassembly of the module and an AC reset the watch started showing the time (I do not have a shot unfortunately). I was pleased but some issues still existed: the watch was running too fast, and I could not cycle through the modes of the watch with the Mode button. The running too fast I suspect it has something to do with the adjustment potentiometer or with the small capacitor next to the crystal. One of them is faulty as no matter how I tried to adjust the potentiometer the watch ran the same.
   Now I took away the wires in preparation for the regeneration but I have to wait for some supplies in order to do the work.

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.