Digitally Curious - A Vintage LCD Watch Blog

Digitally Curious - A Vintage LCD Watch Blog

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  • Tuesday, February 10th, 2009 - 7:16 pm
  • Casio CA-901 [134] Calculator Game Watch

  • It's been a while since the last update! I haven't shown any of my calculator watches on this site so far, so here is a recent acquisition.

    This week's watch is the Casio CA-901 Calculator Game Watch! This is a wonderful model from 1981/82.



    Wow what a faceful, huh? The watch has a pretty busy display and dial, with 4 buttons on each side and a 12 key keypad on the front. Why so many keys? Well you'll find out later in this entry. :)

    Let's examine its construction first.



    The watch casing and side buttons are chrome plated base metal. The case back and band are stainless steel. The front features a glass crystal and a metallic keypad with a rubber membrane underneath (invisible). The glass is held in with a tight fitting gasket and the keypad is held in with 4 screws from inside the case; there is no glue anywhere on this watch! The module inside is held together with screws, typical of very old Casio modules.

    Because the bezel is chrome plated, it is very difficult to find this watch in such good condition. I only managed to obtain one by buying a mint looking CA-901 with a broken module and a scratched up CA-851 with a working module. Then I simply inserted the 134 module from the CA-851 into this CA-901 and now I have a mint condition CA-901!

    Ok let's walk through its many many features.


    First you start with regular timekeeping. Unfortunately, the 134 module is not Y2K compliant, so I had to trick the watch by setting the year as 1981 to get the day/date to show up correctly. I suppose the Casio engineers thought that this miracle would cease before 1999. That's a joke and if you don't get it you need to look at some old Casio advertisements.

    Stopwatch with lap time,


    Alarm and hourly signal,


    Hold on a minute, this is not your ordinary alarm! Most people don't know this, but this watch has an adjustable tone alarm. If you press the "Adjust" button while holding down the "=" button, you can increase the pitch of your alarm sound. Eventually your alarm will sound like a man trying to sing in falsetto, then a mouse, then a mouse singing in falsetto. It has 10 different tones in total.

    Dual time,


    And game!


    The game is commonly called the "digital invaders" game. A random sequence of numbers "fly" in from the right side, and you have to shoot them down by matching the numbers. You gain points by shooting down the enemy and extra points for shooting down the UFO, which is shown as "n".




    Oh no here comes a "5"! Let's shoot it down by arming our "canon" with "5" and fire.

    Now, the game controls are not intuitive. The keypad keys loose their individuality in game mode. The 6 keys on the left side become the "ammo toggle" switch, and the 6 keys on the right side becomes the fire button. When you need to shoot down a 5, you have to press any key on the left side 5 times then press any key on the right side once. If you want to shoot down a 7, you press any key on the left side 7 times, and then press any key on the right side once. Now, if you want to shot down a 7 after shooting down a 5, you press any key on the left side 2 times and then press any key on the right side once.

    Do you get it now? No? Eh. ;D Moving on then!


    One of the left side buttons (the 3rd one from the top) is dedicated to the calculator function. Pressing it will put you into the calculator mode from any of the watch modes, including the game mode. Pressing the button again exits the calculator and spits you out into regular time mode.


    The calculator is a basic 8 digit calc. You may think that's nothing special, but you have to remember this is the early 80's. How can you fit a calculator into that thing, AND put a game into that same package?? WOW!

    Of course, there were some compromises. For example, the watch will store your best game score so far. But if you use the stopwatch, the best score will be erased. I guess there was some sort of memory limitation using 1982 technology.

    Oh by the way, this watch has several twins. There is the CA-851, CA-85 and CA-90, which all use the 134 module. And each of those have some color variations. My particular CA-901 has a blue-themed keypad and crystal, but I have seen silver/black colored versions as well. There is also the CA-86, which is ultra rare!

    By the way, you can view the manual here by searching for "134": http://www.digitalwatchlibrary.com/index.php/DWL/manual_search/

  • Filed under: watch
  • Comments!
  • » Just dug my old CA-90 from out of my loft. Bought in 1982 for £19.95 good write up. My recoprd score on the game was 193040 - I wrote it in the manual on a blank page. Going to buy some new batts see if it works. I did try this once before and no signs of life as I recal.
  • by: Steve, submitted Wednesday, June 3rd, 2009 - 3:18 pm
  • » i have a question,

    I have a old ca-901 casio
    and for a long time the batteries are empty
    for precorsion i took the old ones out i can not find wich model i need to buy i placed two new batteries now i can only see the display in a angle sound and light is working light is poor

    can you please help me with the batery model
    and suggestions ?

    best regards
    Roger
  • by: roger ciapponi, submitted Sunday, July 5th, 2009 - 8:07 am
  • » Roger Ciapponi - you will need two batteries of the type UCAR/RENATA 389 for your CA-901!.
    Battery type 390 will do as well but might not last as long as they are "low drain" and the 389 are "high drain" suitable for power consuming watches
  • by: Andy, submitted Sunday, September 13th, 2009 - 3:49 pm
  • » I bought two batteries that at least fit into he watch. They were 1.55 V each and the display lit up nicely, unfortunately a minute is only 15 or so seconds long. What is the right voltage thaat makes a minute a minute?
  • by: Andy, submitted Wednesday, October 14th, 2009 - 12:52 pm
  • » You need two 389 or 390 batteries, also known as SR1130SW.
  • by: admin, submitted Wednesday, October 14th, 2009 - 1:23 pm
  • » Congratulations!!! I am from Brazil and I had one like this - grandmother present - I was looking for a picture of my old watch and found your site... Real good! You say everything about this old masterpiece...
  • by: Pospiesz, submitted Saturday, October 30th, 2010 - 6:47 pm
  • » Im looking for the casio ca 86, please if somebody help me appreciated that.
  • by: Angel, submitted Thursday, January 28th, 2010 - 7:06 pm
  • » roger ciapponi, submitted Sunday, July 5th, 2009 - 9:07 am

    - What was the problem? The battery? Cos' I got the same problem. I got two new pairs of the battery (SR1130W, 1.55V, 389) but its not working. If I hold the batteries in their slot its ok, I can see the display well, but if I put on the back I can't see, only in an angel. If anyone got an idea what is the problem, and what can I do please help me! Thanks!
  • by: Adam , submitted Thursday, May 20th, 2010 - 4:23 pm
  • » For Adam,
    From memory, when you replace the batteries, you have to "reset" the watch. there is a little hole inside, next to the batteries that has to be shorted to the case or pressed down (sorry, can't remember that far).
    Good luck!, I wish I kept mine.
  • by: ammlione, submitted Friday, August 27th, 2010 - 7:50 am
  • » I have a CA-901, used to wear it at school (I'm now in my 40's). Sadly, the display has faded, so it's hard to read. Still got the original case it came in along with the Instruction booklet.

    Some pics of it on my flickr account: http://www.flickr.com/photos/nicetrainers/sets/72157624418412302/
  • by: Keith, submitted Saturday, July 17th, 2010 - 5:39 am
  • » Hi,
    I have discovered my CA-901 from my schooldays, and had the batteries replaced. Unfortunately the adjuxt button didn't work and I was unable to set the time or date, any suggestions?
  • by: Lewis Shobbrook, submitted Saturday, September 18th, 2010 - 3:03 am
  • » My parents bought me one CA-901 when I was a kid. I still remember how much I enjoyed the game. Recently I got two new batteries, and the watch works well. I have read from you that date can be changed by setting the year as 1981. However, my problem is I do not know how to set the date. Which buttons do I have to press? Thank you.
  • by: Agustin, submitted Saturday, September 25th, 2010 - 5:19 am
  • » I accidentally found the ten different alarm pitches back in the 6th grade when I owned the CA-90! Was it written in the manual?

    FYI: I just bought one on ebay for $44... can't wait to fire it up. what is the best way to lube the side buttons so they don't stick?
  • by: jim Craft, submitted Wednesday, September 29th, 2010 - 12:09 pm
  • » I loved this watch and was determined to get to the end of the game. It took a long time but it was a bit of a disappointment actually, it just went back to the start. I did manage to go right round twice once but it was hard.
  • by: Graham Scott, submitted Monday, April 25th, 2011 - 1:00 pm
  • » I bought the CA-85 when it first came out in 1980. I played Digital Invaders. The max score was 1,000,000. I wanted to see what happened when I reached it. It cycled back to zero. It took me the better part of 8-9 hours of continuous play to find that out. Got cramps in my thumbs as I had to alternate between the left and right. Haha!
  • by: John Ferrer, submitted Monday, January 2nd, 2012 - 1:44 pm
  • » I owned a CA-90 back in 1981. The game was a hit with family and friends. I remember my best friend's 6-year old daughter who was enamored withe watch's buttons (calculator watches were a novelty back then). I also remember playing the game one night wanting to know what happens when you reach 1,000,000 points. After 8-9 hour of continuous play I found out that it recycled back to zero. The prices I paid to find this out were two sore thumbs and an upset wife who was waiting her turn to play the game (she eventually ended up going to sleep).
  • by: John Ferrer, submitted Friday, January 6th, 2012 - 9:02 pm
  • » Is there anyone who knows the total production number of these quite rare watches?
    All speaking about rare and ultra rare. What are those numbers (millions pieces)?
    Just wondering.
  • by: Paavo, submitted Wednesday, January 18th, 2012 - 5:28 pm
  • » I bought this back in the early 80s when i was about 9 -- saved up for months! loved this watch!
  • by: dave, submitted Wednesday, August 1st, 2012 - 8:39 am
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