(Topic ID: 133342)

Help ID Upgraded system 3 CPU


By 04barb

3 years ago



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  • 6 posts
  • 3 Pinsiders participating
  • Latest reply 3 years ago by viperrwk
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    #1 3 years ago

    Hello,

    I think I have an upgraded system 3 cpu board, however I don't see the cut and jumper that should be there. Can anyone help?

    IMG_20150716_102318.jpg

    IMG_20150716_102329.jpg

    IMG_20150716_102348.jpg

    IMG_20150716_102409.jpg

    IMG_20150716_102442.jpg

    #2 3 years ago

    That is a system 4 MPU (there is a horizontal IC socket under the batteries).

    #3 3 years ago

    I see so the board began life as a system 4 and was not upgraded? I just suspected it was because its in a Aristocrat shuffle alley, but the driver board says it was in a firepower. Also, I need to replace the CPU, because I replaced the socket and installed the chip in backwards. What CPU chip does it take? System 3 calls for a 6800 but since its a system 4 would it call for a different one?

    #4 3 years ago

    system 4 uses a 6800 cpu chip.

    The WMS mods specified to be done to a s4 chip is in the reset section and around around the clock crystal. I see the reset mod has been done, i can't tell about the clock mod. The clock mod adds a cap around the clock circuit.

    #5 3 years ago

    thanks for the info

    #6 3 years ago

    The Disco Fever (last Sys3) schematics on IPDB do show two different versions of the schematic and the BOM - there's an optional socket for IC26 below the batteries and the schematic is marked "3A". This shows a 3.3uf tantalum cap (C27) in the reset circuit:

    http://mirror2.ipdb.org/files/686/Williams_1978_Disco_Fever_Schematics_paginated.pdf

    The changes to the reset circuit are in the manual amendment:

    http://mirror2.ipdb.org/files/686/Williams_1978_Disco_Fever_Manual_Amendment_16P_482_110_September_1978_bad_copy.pdf

    where C27 is removed and other changes are made.

    This essentially turns the late 3A board into a Sys4 board. Early Sys3 boards are missing the socket at IC26 entirely as Andrew indicated. Your board does not have C27 indicating the reset circuit has been upgraded.

    The base board p/n for Sys3A and Sys4 is the same - 1B-2001-133.

    Early Sys3 board:
    http://ipdb.org/showpic.pl?id=686&picno=16660

    Sys3A board:
    http://ipdb.org/showpic.pl?id=558&picno=16642

    Sys4 board (socket included for IC26):
    http://ipdb.org/showpic.pl?id=1780&picno=19197

    viperrwk

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