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TECH : 1702a Eprom Voltages

Discussion in 'Electronic Design' started by [email protected], Sep 17, 2006.

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  1. Guest

    Hi All,

    I have in a 1978 model pinball machine, one 1702a.

    I would like to backup it contents, but my eprom programmer works with
    2716 and later.

    My question is -

    When I probe the cpu board with a scope, around the eprom, I was
    expecting to find 5, -5 and -12.

    I only find +5 and -12.

    Can I power this device from an external -12 and make a adapter to then

    read its contents like a 2716.

    I can then program a 2716 and using a couple of sockets, rewire for the

    2716 in place of the 1702a.

    Any help appreciated.

    Kind Regards, Garry
  2. J.A. Legris

    J.A. Legris Guest

    Here's a data sheet for an MM1702A, but it uses -9V not -12.

    If it's only 256 bytes, just set up a bank of 8 DIP switches for
    addresses, some LEDs for output, and read out the contents manually.
    For posterity, you may want to have someone take your picture as you do
  3. Should be +5V and -9V. Datasheets from Intel and MOSTEK are
    available here.

    Better you make an adapter generating -9V from +5V, simple job for
    the MC34063A. Later EPROMs, like 2716, do just this on chip.

  4. Guest

    Thanks guys,

    I will attempt to use a small Z80 trainer I have and wire in a dc-dc
    converter to get -9 from this 5volt only system.

    This is a handy little system that allows direct connections to the bus
    via a breadboard.

    Regards, Garry
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