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Thread: Rev 4 Apple II with weird colour issue

  1. #1
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    Default Rev 4 Apple II with weird colour issue

    Not sure what is going on. Basically the colors on this II seem 'wrong'. When you play something like Carmen Sandiego it's like blues and such are missing. This is the color pattern it generates from the diag disk:

    20191008_195748.jpg

    The other machines vary slightly but otherwise agree on the general tones. Here is one from my II+:

    20191007_210251.jpg

    The machine seems to work fine otherwise. I've tried swapping all the chips I could find that were directly involved in color.. but so far without success.

  2. #2

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    I usually use the following program to test the colors:

    10 GR
    20 FOR I = 0 TO 15
    30 COLOR= I
    40 VLIN 0,39 AT 2 * I
    50 NEXT

    Have you tried rotating the color trim capacitor on the Apple 2plus motherboard? And/or the hue control of your TV/Monitor?

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    Yeah.. it doesn't seem to be a huge problem. If you look at a graphic, say, the police in Carmen Sandiego... on most of my Apples their uniform is solid blue and their skin is kinda pink or red. But on this one apple their uniform is green, and it's like they're 'interlaced'.. missing a line every other line.

  4. #4

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    Quote Originally Posted by falter View Post
    Yeah.. it doesn't seem to be a huge problem. If you look at a graphic, say, the police in Carmen Sandiego... on most of my Apples their uniform is solid blue and their skin is kinda pink or red. But on this one apple their uniform is green, and it's like they're 'interlaced'.. missing a line every other line.
    Interlaced does not mean missing lines. Anyway I understand what you mean though it is not well seen on these rotated pictures. Are there missing lines if you switch to a monochrome monitor? Is the text or lowres mode the same with missing lines? What was repaired before in this Apple2?

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    Yeah the forum software rotates. I don't know why or how to fix. It's been doing that for a couple of years. I'll use Carmen as an example here just to show the difference. And yeah interlaced was wrong word - scanlines? Here is the police on a normal Apple II:

    police-good.jpg

    And this is how they come out on mine. I'm sorry I can't get a better pic but the refresh rate on the monitor forces me to pull the cam in close to get any kind of focus.

    police-bad.jpg

    They're all... pixelated. And wrong color. Green instead of blue.

    Here's the intro screen as it should appear normally:

    carmen intro good.jpg

    And on this Apple II:

    carmenintrobad.jpg

    It's just slightly off, slightly more pixelated. Adjusting the color trim only changes the intensity of those colors, not their hue.
    Last edited by falter; October 9th, 2019 at 07:13 AM.

  6. #6

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    All scanlines are there nothing is missing. Can you verify one by one that ALL TTL chips are as specified and not having different number/marking. There are many TTL counterparts that have inverted outputs/inputs...

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    I'm suddenly recalling now when I got this machine it would not post properly or something.. I ended up swapping a couple of same model ICs around between sockets and got it to work (I'm guessing one of them half failed but still had part working). Wish I'd noted it. But I wonder if the non working part of the bad chip maybe is causing this.

    I swapped all the chips that handle color last night with known good.. no effect. But I'll do what you suggested and just look things over again, check correct specs.

  8. #8
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    You're not generating blue/orange. Looking at the schematic, there's a shift register (A11) that produces a 1 clock-cycle delay to turn green/magenta into cyan/orange.

    If A11 failed, most likely you'd see white or black for those pixels. I would think a bad DRAM chip would cause other symptoms (like your program crashing). If the shift registers at B4 and B9 were bad, you wouldn't see the proper image in green/magenta either. But the multiplexer at A9 and the shift register at A10 might be candidates for a stuck bit. At any rate, that part of the circuit may be worth a look. Also, it probably wouldn't hurt to run a memory test to exclude a bad DRAM chip, just in case.

    Dave
    Last edited by dfnr2; October 9th, 2019 at 08:18 AM.

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    Thanks for the insight Dave.

    Last night I did have a couple odd situations. Ie it would render the graphic of the crook andncops running across screen but it would have the body of the cop stuck in the lower right corner while his legs ran away, etc. I should check the ram again.

  10. #10
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    I tried swapping A9, A10 and A11 with known good.. it did produce a color change:

    IMG_4685.jpg

    Still not right though.

    Running RAM tests but so far they are coming back ok.

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