I’ve made it a habit to wear a watch whenever I go out and I’d like to share the certain modifications I’ve made to suit my needs.

CA-53W

The watch I choose to wear is the Casio CA-53W-1 Black Data Bank Watch.

It’s a digital calculator watch introduced in 1988 that’s still being manufactured and sold to this day. While many calculator watches with even more features preceded it, the CA-53W was aimed away from the luxury market and designed to be affordable. This helped it to become the only calculator watch (to this day) to sell over a million units as well as the only one to be in continuous production for 40 years. It has since appeared on the wrists of many pop culture icons and has become an icon in of itself (note that Marty McFly wears a CA-50 in the first Back to the Future).

It’s peak retro-cool; it hints at my engineering background as well as my love for film and TV props. However, as aforementioned, this watch does have room for a few improvements.

NFC Tag

A popular mod for the popular watch in the world (Casio F-91W) is the addition of an NFC tag sticker behind its display. The same mod can be done to the CA-53W and its colored variants. However the newer units, like the one I have, appear to use a different keypad layer which significantly blocks RF signals (this is corroborated by the comment section in the video above).

After a lot of experimentation and a few destroyed NFC tags, I’ve found that trimming the clear edges of the NFC tag sticker and placing it as close as possible to the bottom of the LCD display gets the best readings. It’s range is very significantly decreased when it’s inside the watch but it is still scannable if you rub the watch against scanners.

I’ve currently written the URL to this portfolio website to it but the possibilities are endless.

IVA Strap

After watching Adam Savage show off a Nasa themed watch a fan modded for him (I don’t think he has an online prescence), I knew I had to get The Skylab ’73 IVA Strap by Haveston. Orange is my favourite color and I loved the idea of strap modelled from historical space equipment.

For the authentic space equipment experience, I chose to the 22mm extended variant of the strap. I often wear multiple layers when going out and have to pull up my sleeve to check the time but with the extended length, I can wear the watch over my coat and check the time comfortably one-handed. The lug width of the CA-53W is 20mm but as the thick strap would require adapters anyway, I decided on the 22mm variant as I felt wider straps would be more comfortable. I got the straps straight from Haveston (they’re located in Britain so the shipping was equal to the price of the strap, bringing the overall cost of the strap on par with the base watch itself) and black square-shaped unamed metal 20mm to 22mm lug adapters from Aliexpress.

The lug adapters I chose were perfect for the CA-53W. Their shape and color blend seamlessly into the case of the watch. Interestingly, I was mistakenly (?) shipped 2 identical pairs of adapters and corresponding quick release springbars. However, all the included springbars for 22mm lugs so I had to use the originals. While slightly more difficult to remove, I think I prefer the low-profile look of the orignal springbars anyway.

However, I do have some mixed feelings about my strap. The build quality isn’t perfect: there’s a couple of weaving faults along the strap and the printed text is already rubbing off. Also, while it is nice to be able to wear the watch over my jacket, the extended length means that I can’t wear it tight around my naked wrist.

Regardless, I am overall complacent with the strap. The hook and loop closure is much more convenient and adjustable than a buckle. The nylon material dries a lot better than the original resin strap which always trapped water underneath when I washed my hands.

Backlight

One glaringly missing feature of the watch is a backlight. The watch is impossible to read in the dark. There’s plenty of examples of people swapping existing backlights with brighter LEDs, adding a second backlight, adding backlight reflectors and adding backlight diffusers to their watches. I could only find one example of someone adding a backlight to a watch that doesn’t have one at all. Coincidentally, it was a CA-53W mod. As Auxiliary Panther suggests, I decided to “make a better version”.

While the LED package used isn’t specified, after measuring around inside the watch, I decided on the 0805. As for the wavelength (color), instead of UV, I chose red. It’s less disruptive to nightvision and orthochromatic photography film is not sensitive to it (although most modern film is panchromatic).

Instead of drilling a hole in the center like Auxiliary Panther, I filed a notch into the side of the PCB (circled in orange) to put my LED on the side of the display, like in the F-91W. Lighting from the side also meant I didn’t have to scratch the white background off the LCD. I did also have to carve out more space for the LED on the black “battery layer” of the watch so that the pieces would all snap together again (not pictured but I do not wish to open the watch up again).

The wiring is exactly the same as Auxiliary Panther‘s; I soldered positive to the positive pad (circled in red) and dangled the negative wire in front of the B button contact.

Just like in Wrist Action’s F-91W mod, I added some foil tape to the side of my watch. I figured if I’m not coating the back with luminescent paint, I’d give the best change for my watch to shine by adding foil. Unfortunately, while trying to fit the foil tape in, I detached the zebra connector off the LCD. While this doesn’t break the screen, it does make reassembly a bit fiddly as I have to make sure the connector stays in place.

Finally, I was able to snap and screw everything back into one piece. Also pro tip for taking apart digital watches: clean the inside of the window with alcohol and a tooth pick; it’s the best way to get rid of any residues and dust so the display isn’t smudgey.

Overall, I’m really happy with this upgrade. While not evenly lit, I can very much read the time in the dark now. I consider this upgrade essential if you want to daily drive a CA-53W. I bought the LEDs in a pack of 10 so please commission me to upgrade yours.