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Thread: Apple IIe PAL (1982)

  1. #1

    Default Apple IIe PAL (1982)

    Hi Folks,

    I have a couple of Apple IIe's for restoration. I have made a start on the first system. I have got to the point I am now getting random characters on screen. I assume it has faulty RAM on board. The 3x2764 mask ROMs all failed to read properly and have been replaced already.

    I have found a post by David M from this forum with a link to a RAM test routine he wrote. I am about to go and program this 2764 ROM and see what result I get as my next step.

    Would anyone be able to tell me what memory locations the RAM IC's reside at. I am hoping I can test them via a fluke 9010, but I might need input from experts here: will the MMU get in my way of accessing RAM. Ultimately I am hoping to only replace the failed RAM chip/s, but identifying them appears to be my problem at the moment.

    Thanks,
    Daniel

    mac4.JPG
    Last edited by nauseous; February 5th, 2020 at 12:13 AM.

  2. #2

    Default

    Hey All,

    Had a win and the apple now boots and shows Apple ][ on the screen. I ended up removing and socketing all the ram ic's and replaced a few bad ones. The diagnostic ROM passes both RAM and ROM checks.

    Now I have a problem with keyboard input. The reset and control keys work to reset the board as expected, but no other keys work. I am wondering if it could potentially be the wrong Keyboard ROM... The system came with 342-0150-A but a leg had come off due to rust, so I haven't attempted trying to read it. I also haven't been able to find this exact ROM online. That being the case I burnt a new ROM 341-0150-A..

    With my limited knowledge before I start to look at the encoder I will try get a read from the original keyboard ROM and check if it show's any differences to 341-0150-A...

    20200206_195143.jpg

  3. #3
    Join Date
    Jan 2012
    Location
    Connecticut, USA
    Posts
    2,821

    Default

    Quote Originally Posted by nauseous View Post
    Hey All,

    Had a win and the apple now boots and shows Apple ][ on the screen. I ended up removing and socketing all the ram ic's and replaced a few bad ones. The diagnostic ROM passes both RAM and ROM checks.

    Now I have a problem with keyboard input. The reset and control keys work to reset the board as expected, but no other keys work. I am wondering if it could potentially be the wrong Keyboard ROM... The system came with 342-0150-A but a leg had come off due to rust, so I haven't attempted trying to read it. I also haven't been able to find this exact ROM online. That being the case I burnt a new ROM 341-0150-A..

    With my limited knowledge before I start to look at the encoder I will try get a read from the original keyboard ROM and check if it show's any differences to 341-0150-A...

    20200206_195143.jpg
    I have had that exact problem a couple times (reset and control key functioning, but no primary keys) It turned out to be a bad keyboard encoder chip. I bought a couple from ebay :
    https://www.ebay.com/itm/1PCS-KR9600...72.m2749.l2649

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