Casio JP-100W (Yellow) – Restoration

Every restoration project starts with a story. This one began on Facebook Marketplace, where I spotted a Casio JP-100W (Yellow) listed for $63 shipped. The seller wasn’t in the mood for deals — we went back and forth in negotiation for a couple of weeks, but he never budged on the price. In the end, I gave in and paid what he asked.

At first glance, the photos told me it wasn’t going to be an easy project. The strap was missing, the case looked like it had survived a concrete mixer, and the digits on the LCD were so weak they were barely visible.

Still, the JP-100W caught my attention. It’s one of those quirky Casio experiments from the late 80s and early 90s, fitted with a pulse-checker function that felt like pure sci-fi back in the day. For collectors, these oddball models are half the fun — not always practical, but packed with personality and history.

So, I took the gamble. The goal? To see if I could bring this neglected watch back to life and get that pulse checker ticking again. ⌚🛠️

What was the initial condition of the watch?

When the JP-100W finally landed on my desk, the first impression was… rough. The watch had clearly lived a hard life, and maybe even a failed “repair attempt” or two. Here’s what I was looking at:

• No strap at all. It came bare, which made it look more like a spare part than a wearable watch.
• Scratched case and glass. The yellow resin had lost its shine, and the acrylic crystal looked like it had been polished with gravel.
• Faded LCD digits. Numbers were barely visible, which is a common issue with aged Casio screens.
• Dead pulse checker. The signature feature of this model didn’t respond at all.
• Sticky buttons. None of the pushers would spring back after pressing, making the whole interface unusable.
• No sound. The piezo buzzer was silent, which always feels like the soul of a vintage Casio is missing.
• Dirt everywhere. The case, module edges, and button gaps were filled with grime that looked like it had been collecting for decades.

Honestly, most people would have thrown this into a junk drawer and moved on. But I’ve learned that even the worst-looking Casios often hide potential. All it takes is patience, the right tools, and sometimes a little bit of improvisation. 😅

How did the restoration process go?

I broke the work into small steps. That way I could test progress as I went and avoid turning the JP-100W into a permanent parts donor. Here’s how it went:

Step 1: Strap replacement

The watch came naked, so the first thing was to give it something to sit on. I ordered a simple black strap from Amazon for $10. To mount it, I also bought a pack of spring bars for $9. It’s always worth grabbing a full pack — you’ll need them sooner or later with Casios.

Step 2: Case and crystal polishing

The yellow resin case and acrylic crystal were in terrible shape. I went through a wet-sanding sequence: 600 → 800 → 1200 → 1600 → 2000 → 2500 grit. After sanding, I applied Polywatch to buff the crystal back to a clear finish. The resin case also regained a bit of shine, which made the whole watch look less “rescued from a toolbox.”

Step 3: Screen improvement

The faded LCD digits were the biggest visual problem. To fix this, I cut a small piece of polarized film and applied it directly on the LCD inside. The whole roll cost $6, but I only used a tiny portion. The effect was instant: digits became sharp and legible again. (Fun fact: by changing the angle of the film, you can even create a “negative display” effect.)

Step 4: Sound repair

The buzzer wasn’t making any noise because the contact spring was missing. I scavenged a small spring and fitted it between the piezo and the module. Suddenly, the JP-100W had its “beep” back. Without that sound, a Casio just feels… wrong. 🔧

Step 5: Button fix

The pulse-check button wasn’t responding. Another small spring solved this, restoring its click and making the pulse sensor functional again.

Step 6: Battery plate repair

Inside, one of the plastic clips holding the battery plate had broken. Instead of letting the plate wobble, I carefully used a soldering iron to re-melt and reattach the clip. This secured the battery and stabilized the power connection.

Step by step, the JP-100W started to come alive.

What challenges came up during the restoration?

Not everything went smoothly. A few parts of this project reminded me why restoring old Casios is equal parts patience and problem-solving:

• Signs of a past repair. Someone had clearly been inside this watch before me. That meant missing springs, broken clips, and contacts that weren’t sitting right. Instead of undoing their mistakes, I had to improvise — scavenging small springs and carefully rebuilding what was gone.
• The faded LCD. This was the big question mark. Sometimes an old Casio screen is too far gone. Luckily, the polarized film trick worked perfectly here, but cutting and applying it neatly inside the module took steady hands. One wrong angle, and the digits would look distorted.
• Broken battery plate clips. This was the scariest part. Without those clips, the battery would never stay secure. Using a soldering iron on fragile 30-year-old plastic is risky, because you get only one shot before it melts into nothing. I went slow, kept the heat low, and managed to lock the plate back in. Big sigh of relief. 😅

These little roadblocks are what make restorations satisfying. Every Casio teaches a new trick, and every “unsalvageable” part is just another challenge to work around.

What is the final result?

After a few evenings of work, the Casio JP-100W (Yellow) came back to life. The goal was not to make it new. The goal was to restore its function and character.

The LCD digits are sharp again. The polarizing film did the job.
The case and crystal look clean. The heavy scratches are gone. The yellow resin has a fresh shine.
All buttons work again. The pulse checker responds with a click.
The sound is back. A Casio without beeps never feels complete.
With the new strap fitted, it looks like a watch again.

It is not perfect. But it is wearable. It is functional. It carries its history with pride. And most important: it has its pulse back. ⌚✨