Anyone Ever See A Mac 128k Upgrade Like This?

Discussion in 'Apple Collectors' started by cocacolakid, Oct 7, 2011.

  1. cocacolakid, Oct 7, 2011
    Last edited: Oct 7, 2011

    cocacolakid macrumors 65816

    cocacolakid

    Joined:
    Dec 18, 2010
    Location:
    Chicago
    #1
    I picked up an original Macintosh from the original owner. It was upgraded to 512k in 1985. It's currently showing a checkerboard display, so I opened it up to take a look inside.

    I've never seen a 512k upgrade that looks like this. Anyone else ever see one like this?

    It also had a PRAM battery that got old and leaked onto the ROM chips on the logic board. I'm going to clean it and see if that fixes the checkerboard.

    [​IMG]

    Larger photo:

    http://www.flickr.com/photos/58469634@N00/6221528120/sizes/l/in/set-72157627711600177/
     
  2. MacTech68, Oct 8, 2011
    Last edited: Oct 8, 2011

    MacTech68 macrumors 68000

    MacTech68

    Joined:
    Mar 16, 2008
    Location:
    Australia, Perth
    #2
    I haven't seen one done in that particular fashion but that's pretty much how the circuit works to add the extra address line.

    AFAIK, Apple never did upgrades to 128K MLBs this way (adding the 74F253). This was the way third parties upgraded the MLB to 512K

    When I did them, I had a small circuit board that had pins that fitted into the row of solder pads next to the CPU. Perhaps the method pictured would have been cheaper.

    It's certainly very neatly done. :)

    Looking at the ROM sockets, it might be better to get the sockets replaced.
     
  3. cocacolakid thread starter macrumors 65816

    cocacolakid

    Joined:
    Dec 18, 2010
    Location:
    Chicago
  4. PowerMac G4 MDD macrumors 68000

    PowerMac G4 MDD

    Joined:
    Jul 13, 2014
    Location:
    At the intersection of Conch and Coral.
    #4
    Sorry to reply to a several year-old thread, but do you know how one can reverse such an upgrade? My "128k" was upgraded in a similar manner, and I want to reverse the upgrade so that it's back to original 128k specifications.
     
  5. havokalien macrumors 6502a

    havokalien

    Joined:
    Apr 27, 2006
    Location:
    Kelso, Wa
    #5
    Just remove those parts. Leave the ram and it will go back.
     

Share This Page