Casio SDB-500 – Restoration

This Casio SDB-500 came to me in a special way. One of my Instagram followers, Ken from Sweden, reached out because he wanted me to repair a few of his Casios. Along with the watches he needed fixed, he also sent me a small gift box full of extra pieces. Inside was something I didn’t expect: a black SDB-500 with grey buttons, one of my personal favorites from Casio’s late 80s sport databank line.

The watch was working, but far from perfect. That made it even more exciting. Restoring it felt like a challenge and a treat at the same time. This model has a strong place in Casio history, combining databank features with a sports-oriented design. For me, getting one as a gift from another collector was a big moment. It shows how our small online community connects people across countries, all thanks to these quirky digital watches.

Like many other SDBs, this one carried a funny reminder of its age: the calendar ended in 2019 😅. It is one of those small quirks that makes Casio collecting special. The software limits may be outdated, but the hardware can still be brought back to life.

I decided to give this watch a full refresh. Scratches, missing sound, stopwatch issues… plenty of work ahead. But that is what makes a project like this rewarding. And as soon as I saw it, I knew: if I could bring it back to life, it would become my number one daily Casio.

What was the condition of the watch when it arrived?

When I first opened the package, the SDB-500 looked like it had seen a lot of wrist time. The module was alive, but a few things were clearly wrong:

• The stopwatch mode was behaving strangely.
• The watch had no sound, because the small buzzer spring was missing.
• The acrylic crystal was full of scratches.
• The resin strap was old and worn out.

Visually, the case still had its original shape, but dirt and small marks made it look tired. Collectors know this look well: a good candidate for restoration, not a parts donor.

How did I restore the Casio SDB-500?

I wanted to bring this watch back as close as possible to factory condition. The restoration covered cleaning, polishing, repainting, electronic fixes, and final assembly.

Disassembly and cleaning

I removed all four buttons carefully, since dirt often collects under them. The case was washed in a dish soap solution, which is gentle but effective for removing years of sweat and dust.

Crystal and case work

The acrylic crystal had deep scratches. I started with fine sandpaper and then finished with Polywatch to make the surface clear again. For the resin case, I used a white magic sponge. It has very fine abrasion, which restores the original matte look without making the surface glossy.

Repainting the button inlays

One detail I really wanted to bring back was the original paint on the front buttons. From the factory, the left button had a red line and the right button had a blue line. Most watches on the market today have this paint completely worn away. I carefully repainted both inlays, so the watch looks just like it did when new.

Electronics and sound repair

The watch was silent because the buzzer spring was missing. After fitting a replacement, the sound came back. The stopwatch bug was caused by dirty PCB contacts. I cleaned the module board with isopropyl alcohol. After a few assembly attempts, the stopwatch worked perfectly again.

Final assembly

I reassembled the watch and checked the buttons. A fresh strap was fitted, and the watch was tested for all functions. I skipped water resistance testing, because on a 35-year-old watch the gaskets are often weak or missing.

The result: how did the Casio SDB-500 turn out after restoration?

After the full restoration, the watch looked and worked like it had just left the factory. The crystal was clear, the case had its matte finish again, and the buttons showed their original red and blue paint details. It felt like the watch had recovered its identity after decades of use.

Functionality was also fully back. The stopwatch ran smoothly, the alarm and hourly signal had sound again, and all modes switched without issues. For a late 80s module, that was very satisfying to see.

Wearing it after restoration felt special. The SDB-500 is not the rarest Casio, but it has the right mix of style and features that make it fun to use every day. That is why it instantly became my daily Casio number one.

The only limitation that remains is the calendar stopping at 2019 😅. For collectors, this is not a problem but part of the charm. The watch may not know what year it is, but it can still time laps, wake you up, and look great on the wrist.

Restoring this piece reminded me again why I enjoy this hobby. It is not only about fixing functions, but also about reconnecting with history and sharing the results with other enthusiasts around the world.