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Thread: Weird characters on II+

  1. #1

    Default Weird characters on II+

    Hi,

    With my newly arrived ROMS I've NEARLY got this Europlus fixed but not quite.

    The system boots but the characters are all screwed up. For example...



    The text SHOULD say :

    APPLE ][

    ]THE QUUICK FOX JUUMPED OVER THE LAZY DO
    G
    ]SYNTAX ERROR
    ]

    (keybounce is bad on the U character)

    It's like the characters are mirror images but with the furtherest left hand side of the character block missing.

    Anyone know what causes this? I don't think it's any of the ICs because I've done a full substitution from a working machine, including the character generator. I suspect a static component, faulty socket or a dry solder joint maybe. But where? The symptom is distinct, and hopefully someone out there who knows Apples can tell me exactly where in the circuitry things are shifting phase (or whatever) and what I should test.

    Thanks in advance.

    Tez
    Last edited by tezza; October 21st, 2008 at 12:00 PM.
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


  2. Default

    I've seen this one before and always thought the effect was kind of cool. I can't remember the exact fault I had on my system. However, fundamentally what is happening is that the video memory scanner is not picking the right DRAM address for each sequential horizontal pixel. Check the ram address mux (E11-E14, C11-C12) and video scanner (D11-D14). Focus on horizontal parts of these subsystems (E12-E14 & D13-D14)

    I do suspect that video scanner should be ok since vertical and horizontal blanking and hold look good.

    Regards,
    Mike Willegal

  3. #3

    Default

    i can't help you, sorry. but i can't help notice it looks like it's trying to use the gargoyle language font from ultima 6...
    My emulators!
    Fake86 8086/V20 PC emulator: http://sourceforge.net/p/fake86
    MoarNES Nintendo emulator: http://sourceforge.net/p/moarnes


  4. #4

    Default

    Quote Originally Posted by Mike Chambers View Post
    i can't help you, sorry. but i can't help notice it looks like it's trying to use the gargoyle language font from ultima 6...
    Perhaps it's possessed from a previous life...

    Ok, thanks Mike. I'll poke around in those areas.

    Tez
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


  5. #5

    Default

    Hmm..well, I'm totally stumped on this one. Those areas seem fine and the ICs are fine too. No sign of dry solder joints...those sockets seem to be working...it's a mystery.

    The only difference I can see between my test machine and the Europlus is the Europlus has Applesoft ROMS and a different power supply. But that shouldn't contribute to this kind of symptom, should it?

    I'm tempted to replace the Clone ROMs with the AppleSoft ones and screw the clone power supply and board into the Europlus case. It actually fits. Externally it would look like an Apple II+

    But then *I* would know the difference, and when you pop open the lid, you wouldn't see that "Apple II 1979" on the circuitboard.

    It's just not the same

    Tez
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


  6. #6

    Default

    Ok, *STOP PRESS*

    I'd just posted that message above and was sitting here thinking about the problem.

    I had substituted all the ICs from the working clone machine including the character generator. It suddenly struck me that the character generator sitting in the Europlus prior to substitution wasn't the one that was there originally. It was from another clone board. I'd replaced the original one when I first tried to get the Europlus going. The original CG was sitting in a box called "dubious Apple II parts" because it didn't work in the working clone machines...so I suspected it was faulty.

    ..or was it? Hmm..the clones didn't have EXACTLY the same circuitry and maybe, just maybe, the Character Generators in the clones were a little different too.

    I fed the dog, then went up to the computer room for one last throw of the dice. I found the "dubious parts" box and found the orginal Apple II CG. I cleaned the legs, substitute it for the one that was there and switched on the machine....

    ...and got...

    APPLE ][

    ]

    It worked!!!

    So, that was the problem. The clone CG I had in there wasn't 100% compatible with the circuitry. That would also explain why the APPLE CG didn't work in the clone when I tried it at first. Good thing I didn't throw it out!

    Well, the Europlus is going now...at least with nothing else plugged in. tomorrow I'll wire up some disks and run a diagnostic program just to check the RAM and everything else is all OK.

    Ok, I will sleep a happy man tonight.

    Tez
    Last edited by tezza; October 22nd, 2008 at 02:26 AM.
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


  7. #7

    Default

    I don't know if this helps, but as there was a mention of "clone" in your last post...

    In the autumn of 1979ish 2 months after we'd arranged a nasty accident for the teletype, our school Apple][ turned up, however, being cheapskates we ended up with the ITT2020 clone.

    After months of peeking and poking & trying to do screen dumps to disk we realised that there were differences in the pixel mapping between the (documented) apple][ and the undocumented clone. working from basic etc not a problem, but in assembler it left vertical stripes blank when we tried to write to the screen.

    That looks a bit like what you have there. If you have the wrong ROMs in, that could explain it.

    simultaneous postings!
    Last edited by nige the hippy; October 22nd, 2008 at 01:49 AM.
    "Don't it always seem to go
    That you don't know what you’ve got ‘til it’s gone" (BANG )

  8. #8

    Default

    Yes, that was it Nige. The wrong character generator ROM. As you can see, I had that thought myself before you posted.

    I've just played around with the machine a bit more. The keyboard sometimes maps incorrectly so it looks like still one or two ICs to check out before I can give the unit a clean bill of health. I'm looking forward to adding it to the working collection though.

    Tez
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


  9. #9

    Default

    Actually when I posted it I was thinking more about the MOS roms, but character generators being different would make a lot of sense.

    HEY! one advantage of the existence of a CG rom is that it could be substituted for one programmed with... for instance... Klingon script!
    Runic, or maybe even the Apple Rennie Macintosh

    Tee Hee
    "Don't it always seem to go
    That you don't know what you’ve got ‘til it’s gone" (BANG )

  10. #10

    Default

    Yes the applesoft ROMS are defintely different and are non-swappable with the clone machines, which is why I had to order in replacements.

    Tez
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


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