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Thread: My first Rev 0!

  1. #11
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    >>> Dave! Good to hear from you again!

    Yes, it's been a while!

    I got bored the other evening and started to put together a little emulator for the Motorola 68000 Educational Board that you have. Managed to get the TUTOR prompt up. Just need to find a little bit of time to include the keyboard handling.

    Yes, sometimes you can be lucky with a bit of chip 'pulling and pushing'...

    My Apple IIe had a single faulty DRAM - but the fault was quite strange due to the way the RAM address lines are formed.

    The disk controller fault was more interesting however. Some of the pins of the ICs were tarnished - and what had happened was that the metal pin had been 'eaten' clean through (at the microscopic level) so the IC pin itself was floating but (to the naked eye) it looked OK. I deduced which components were faulty and (when I removed the ICs from their sockets) the pins I had worked out were faulty ended up left in their sockets! They were clearly not physically (or electrically) connected to the IC at all!

    Replacing the components - one good working Apple IIe.

    Sockets are good for replacing ICs - but a nightmare for longevity of the machine...

    Dave

  2. #12
    Join Date
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    Hi guys,

    So I did some testing. It does seem like the clock pin 7 is intermittent. I've observed it pulsing on power on, and then stopping and going low. Or not pulsing at all on power on. Or not pulsing and then pulsing a little bit and then stopping again.

  3. #13
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    Ahhhhhhhh

    So we have two Apple IIs with reset keys that don't work. Ugh. I got fooled! This Rev 0 was working the whole time. I think.

    As mentioned, when I would power up, I would sometimes get a solid white screen, or weird color bars, or flashing/changing text. I assumed the solid bars in particular meant computer = bad, because on my Rev 02, which also has the integer ROMs and no autostart, it just dumps random text garbage onscreen until you Reset. Never any solid colors or bars.

    I had wrongly assumed that a very good condition Rev 04 machine I had here had a fully working keyboard. Apparently the reset on it did not work. Only when I borrowed the keyboard from a nearby II+ did I realize my mistake. Even when I have the solid color bars onscreen, if I hit reset, I get the monitor prompt, and integer basic works. Dang!

    I still don't think those color bars belong there. I think there's possibly a chip somewhere that is malfunctioning and putting those up. But at least I know I'm not going crazy now!!

  4. #14

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    So is the clock working or not?

    I seem to recall the early ][ that I used to use would sometimes be in graphics mode on startup. If you can push RESET and then everything works, what happens before the initial reset is inconsequential.

  5. #15
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    The clock is definitely working. I guess when it had some of the graphic screens it wasn't fetching much in the way of instructions.

    If for example I get a screen full of white, if I hit reset, the white turns into ? marks and I've got a prompt. I've got a prompt no matter what when I hit reset and I can use the machine as normal. I get a lot of blinking stuff onscreen too. Sometimes I power up and I get random color bars all over.

    I only wondered about the stray graphics mode being a problem elsewhere, ie. if I go to do something with graphics and it's all messed up.

    Interesting. I wonder if the starting up in graphics mode is something they rectified in later revisions.
    Last edited by falter; October 4th, 2019 at 08:25 PM.

  6. #16

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    Glad to hear you have your Rev 0 almost working. I believe the video generation on the Rev 0 has some anomalies when compared to later Apple IIs. I have found Winston Gayler's The Apple II Circuit Description book to be a good reference on Rev 0 Apple IIs and differences from later Apple IIs.

  7. #17
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    Okay, so after replacing all the original chips and doing the alcohol/repeated keypress trick on the reset key, I can now reset the computer. However, it appears I have some issues in the typing department. For example, when I type 1, I get Q1. Same if I type Q. It's not the motherboard from what I can tell - I can type just fine with another keyboard... seems to be something going on with the matrix?

  8. #18

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    Sure sounds like some foreign object or liquid spilt in between Q and 1.

  9. #19
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    Seems to be slowly improving. I hit every key with some alcohol and a few hundred pressings. I have some keys were the springs have gotten weak and are not fully lifting the key up anymore - that is causing some headaches. My remedy for that, unfortunately is to just take some spare springs I have around from a box full of PET key caps and use those to reinforce the key so it pops up more reliably.

    It's getting there.

  10. #20
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    Somebody on reddit pointed out the bag I have has the 'unbitten Apple'. Is that actually a thing?

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