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.
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.
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! 🙂
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! 🙂