A gadget of the early 1990s...a Casio JP-200W Pulse Check Watch
Last year I found this badly worn Casio JP-200W on a bargain table on a fleamarket. I instantly remembered this model when I saw it, because I always wanted it, when I was a child. As it was only 1 € (!), I simply had to take itwith me.
Scratches everywhere...and no function at all.
I started tearing it down and found some corrosion from battery acid on the circuit board (the turquoise stains).
In the front you can see a tiny lightbulb - there was no other night illumination in lcd watches back then (a technology called "Illuminator" - a blueish backlight - was released some years later, though).
The gold plated contact strips for the LCD module are also good visible - I had to clean them from battery acid, too.
The next pic shows the LCD - some segments are lightly visible and seem faulty. However, it is possible for them to recover after battery power has been re-established for some days.
See the three golden contact springs of the optical pulse rate sensor on the left?
Crystal and case after sanding (I used wet sand paper with descending granulation sizes: 600 -> 800 -> 1000)
After I had finished the sanding I applied some Polywatch and continued polishing for some time (I recommend googling for it, if you don´t already know this great product)...
Then I put a battery in...two contacts near the battery had to be shorted to power the watch up...
And there it was...
A working pulse check watch (okay to be honest some segments are still dead and to restore their finction, I will have to replace the elastomeric "Zebra" connectors between the LCD and the circuit board on occasion).