Casio DW-721: low battery problems

In today's article we will show an unexpected problem found in a classic model, the DW-721 from one day to another without notice and I think it was due to the battery used.

First, we apologize for the poor quality of the photos. It is seen that that day I had the pulse to steal tambourines...

The Casio W-721 is one of the classic models with the magnificent 549 module: dual time, alarm, stopwatch, countdown and the now defunct function rem...

One day, when taking this classic out of the box, I noticed that has the screen as is:

Obviously it was not very normal. The first thing I tried was to press all 4 buttons simultaneously. In some models this causes a "reset", so the watch would return to normal and I would not need to open it.

Unfortunately this was not one of those models and the watch did not respond to pressing any button or combination of them. So all that was left to do was to open it and reset it in the traditional way.

Disassembly begins

Carefully remove the 4 screws that hold the back cover and check that there is nothing unusual inside the watch. The truth is that the battery was the one I had on the day I bought it and I hadn't paid much attention to it.

I dismantle the plate that fixes the battery inside the body of the module to check that it is in perfect condition and that no leakage has occurred that could irreparably damage the watch.

Once extracted and verified that there are no leaks, with the multimeter I check the load, and I find a curious behavior. As I start to measure the voltage of the dick indicates a correct level, but after 2 or 3 seconds, the value falls below 1 volt.

Obviously, this behavior indicates that the battery is in the last ones, so I proceed to change it to avoid unnecessary risks.

I place the battery in its compartment and make a "reset", joining the connector marked "AC" with the positive pole of the battery. I turn the clock over and check that everything has returned to normal.

I take the opportunity to clean the rear seal and re-lubricate it with silicone grease for better hydration.

Place the rear cover carefully so as not to move the rear joint from its correct position and gradually tighten the screws in a cross pattern so as not to force them.