Casio PB-770

In the first half of the glorious 80s, some manufacturers, mainly the Japanese Casio and Sharp, battled for dominance of one of the most creative segment of personal computing: the pocket computers one, made of hybrid machines, halfway between a scientific calculator and a laptop.


Casio PB-770

Recently, I used to peek on ebay ads, and I came across a specimen declared as not working of the Casio PB-770, with its original leatherette case , bought at just 14 euro. If it were not for shipping fees…

The Jewel seemed to have a memory problem because, although having no program stored in its 10 slots, it returned an error code related to a memory shortage.
I feared the worst, since the ram chips installed in these vintage machines are no longer easily available. As a first step, I opened with much patience the case of the Casio PB -770 and I did a quick inspection.
The quality standards of these small computers were not like nowadays ones. The original design often contained coarse engineering errors, having welding of obscene and unreliable flying leads as workaround.
But in many cases these flying leads were just a choice, to save on the cost of motherboard, and produce single-sided printed circuits rather than double-sided ones.
The Casio PB-770, as well as his ​​minor brothers and cousins, is no exception to this rule, proposing some internals to thrill, with colorful wires that perform roller coaster tracks.

Hello World era troppo banale. :)

I inspected the memory chip, taking note of the parts code. Looking for about an hour on the search engines, I could not find any distributor that sells surplus rams of that kind.
I opened the battery compartment, and removed and replaced both operating (of common AA), and backup batteries (a coin type) and… miracle!
That was enough to bring my Casio PB-770 back to life! Probably there were dirty characters in memory that deceived the firmware and, in the absence of power for a few minutes, that information got lost, and memory was found to be perfectly functioning and free.
A lucky break sometimes does not hurt! πŸ™‚

The Casio PB-770 had 8KB of RAM, and was expanded by small size proprietary cartridges, up to a maximum of 32KB which, for the beginning of the 80s, were a real luxury.
The large display with adjustable costrast was a prominent feature, with its 4 lines on 20 columns in character mode, and its 160×32 pixels in graphics mode.
The Casio PB-770 was programmed in BASIC, and had a fairly advanced command set, also devoted to tracking graphs and histograms.
It was possible to store up to 10 different programs in the internal memory, and it was possible to make sure they ran each other, interacting with each other, allowing the programmer to design an extraordinarily flexible and modular software architecture.

Among the accessories, common to the whole PBxxx family, a docking station was available, the FA-11, which provided the Casio PB-770 of a microcassette unit and a four-color plotter. The overall size of all contained a common A4 sheet! Magical 80s! πŸ™‚


  1. Some people would say that this is luck; I think instead that a finding like that (low price, apparently not working) is just a reward for all the time spent scavenging debris in flea markets.
    Nice post! And your English is really good. I want to translate my site but I never have the time to do it…

  2. Hey James! What an honor to have you here! πŸ˜€
    Thanks for the compliments, although in reality I have to share with the author of the plugin I use, and with Google, to which leans. πŸ™‚
    I deal only to revise the translations, and move a couple of adjectives and subjects here and there.
    The plugin in question is Transposh. πŸ˜‰

    • Hi Marcus.
      Thank you very much for your comment and you valuable work on CASette. Much appreciated. πŸ™‚
      Are you aware of some DIY project to interface this pretty tiny beast via arduino or serial usb to a modern PC?
      I only know about some solution that operates over the dear old serial/parallel interfaces.
      Thanks again and welcome to my blog. πŸ™‚

  3. Ciao Gabriele
    I was very fascinated by those little marvels, the Sharp PC-1500 and the more powerful Casio PB-700 and 770.
    I actually learned basic on these machines, and created useful programs, one of which was even published (and paid) on Bit, an Italian magazine of those times.
    My most complex program on the PB-770 was developed to produce organization charts for my company.
    I designed and programmed it to enable the user to input up to 7 levels hierarchy and 9 job title positions boxes across, plus printing all connecting lines and avoiding possible boxes collisions.

    The printer itself was a very fascinating piece of electromechanical miniature machine, plotting in 4 different colors. Once enlarged on a photocopy machine to A4 or Letter size, these little charts were immediately usable, without having to wait for the draftsmen to manually create them.
    I still own one fully working PB-770, complete with the plotter and cassette recorder but unfortunately the little pens, and the paper rolls cannot be found anywhere in the US, at least to my knowledge.
    If anybody knows where to find pens and paper rolls please let me know.

  4. Thank you Gabriele. I’ll check out those links. Years ago, I attempted to “reload” the little pens, by very carefully pulling out the tip and filling the cylinder with ink. I was using standard fountain pens inks so the “reloaded” pens did not always work. May be I’ll try filling the little pens with Ink jet printers’ ink and see it I can get them to work more reliably.

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