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Thread: IBM 5110 power supply schematics?

  1. #11

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    Quote Originally Posted by Hugo Holden View Post
    I really would like to see that circuit if you ever copy it out.Most SMPS's as you know use IC's for the switch mode control, it looks like IBM crafted their own circuit from those interesting modules and discrete transistors, so it's probably a very cool design.
    I happen to come across this picture which matches (i think, I have no idea of the IBM numbering scheme) four of the shiny metal cubes in the PSU:



    From this page.

    Seems to be three transistors and three resistors in there.

  2. #12

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    Quote Originally Posted by MattisLind View Post
    I happen to come across this picture which matches (i think, I have no idea of the IBM numbering scheme) four of the shiny metal cubes in the PSU:



    From this page.

    Seems to be three transistors and three resistors in there.
    That is very good news in that the circuit can be drawn out and the resistors measured and on top of that the transistors could, if required, be replaced with modern surface mount types. So it's likely repairable and probably a logic gate configuration.Even a replica could be crafted with surface mount parts on a PCB as a replacement.

    That kind of design with resistors screened onto ceramic and transistor crystals mounted on to it was a technique to make high reliability and temperature resistant modules. It's also possible some other module types contain surface mount capacitors in them too, depending what the module was designed for.

    I wonder if IBM ever published a book with all their modules in it or whether they were top secret ?

    I think as time goes by its going to be important that these modules get documented as they are are part of computer development and history and it will be required to have the knowledge of them to repair the vintage computers that use them.

    I have also seen IBM modules , some much larger memory ones on a short ISA memory card in my 5155. Working currently, but if they fail it would be good to find a way to repair them or replicate their function and appearance.

  3. #13
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    The 5150 floppy controller used the SLT packages as well, which always seemed to me to be a bit strange, seeing as how IBM was working to use commodity parts for the 5150.

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