• EEVblog #382 – Cambridge Z88 Teardown

    Retro teardown of the 1987 Cambridge Z88 notebook computer from Clive Sinclair
    Running the OZ operating system, Pipedream application, and BBC BASIC

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      • sombody

        The inductor would be part of a boost converter to supply 12V for the RS232.

        • David

          Yup, and some of those parts around the inductor probably form a charge pump inverter for the -12 Volts used for the RS-232.

      • Maalobs

        “..can run off the sniff of an oily rag…”

        My sides…

      • bruno

        At 14:30, what is that component at the bottom right (under the DB9, and between the right-most diode and the resistor to its left)?

        It looks like an SMD cap inside a glass package…

        Also, when inspecting the crystal, isn’t that a whole lot of ringing?


        • JB

          It is a glass cased ceramic capacitor. When I worked for Digital Equipment we used to use them as decoupling capactors (generally one per 74xx chip) and as I recall the supplier was Unitrode. We used the Z5U dielectric type 0.01uF 50V. The body was small compared to most alternative axial leaded components and could be auto inserted into 0.3″ spaced holes.

          You can see a data sheet here – http://www.markoparts.com/enter/data/unitrode.pdf

          • bruno

            Alright, thanks mate.

      • nasos

        the z88 should have onboard eprom programmer so the other use of the boost converter should be for the eprom programming voltage (12,5V)

        The clock may stops in order to read the asic chip the ram and refresh the lcd panel. This technique (to stop the z80 clock) i think it is also used in zx spectrum

        The Z80 is a Z80A CPU and its clock rate is seen in the partnumber z84c0004 (the last 4 is for 4mhz clock ie Z80A cpu).

      • RogerBW

        The non-volatile storage packs were EPROM (as labelled), not EEPROM – that’s why the circular holes exposing the chips, so that they could be wiped by UV, either officially with the eraser lamp or by leaving them in the sun for a bit. The storage tradeoff was RAM (more power, infinitely changeable, volatile) vs EPROM (less power, needed to be erased all at once, nonvolatile) The Psion Organiser handhelds did the same thing in a slightly different physical format, though they got cleverer about flagging deleted records so you didn’t lose the entire previous size of the file every time you wrote something to EPROM.

        Looking briefly at software, Pipedream was a rebadged version of View Professional (or possibly vice versa); ViewPro was available for the BBC Micro series, so you actually had the possibility of exchanging files in a usable format. It’s an all-in-one word processor, spreadsheet, database(-ish) program.

        OZ was reasonably cunning, in that you could suspend any of the built-in applications at any point by jumping back to the index, and resume them later. Not quite multitasking, but not bad.

      • Edward Lye

        I liked this so much I bought another unit as backup. Unfortunately the membrane keyboard was crap and I never got around to building my own replacement keyboard. I built my own RS-232 cable to connect to my Toshiba 1200 FB.

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