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Thread: Apple colour monitor not showing colour

  1. #1

    Default Apple colour monitor not showing colour

    Hi,

    I picked up up a second Apple Colour monitor for a nominal sum the other day.

    It's from an American import and runs on 110v. I'm using a step-down transformer with it. Problem is I can't seem to get colour. The mono image is clear and steady but there is no colour to be seen

    The question is...Would there be something about a 110V American apple colour monitor which is incompatible with my "not made for America" Apples. My Apples are either IIe's (both say "International NTSC" on the boards), a Europlus or Taiwanese clones.?

    Anyone know?

    If not, could be just a bad cap somewhere in the monitor?

    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)


  2. #2

    Default

    Have you tested all of the aforementioned Apples with the monitor? It does sound like some combination should work.

    I get black and white results from European Amiga 1200 composite out on North American displays. It is an expected effect since PAL encodes the color carrier on different frequencies than NTSC displays.

  3. #3

    Default

    Yes, I've tried it on them all but only monochrome is the result. Unlike my other 240v Apple colour monitor which does produce colour.

    From what I can read, colour in Apples is produced in a rather subtle and unorthodox way. Apples not sold in USA are a little different in the video output for this reason (e.g. the Europlus and the "International NTSC" for the Apple IIe). It just may be a reflection of a USA monitor being matched up with non-USA machines.

    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)


  4. #4
    Join Date
    Jun 2009
    Location
    Cottonwood Heights, UT
    Posts
    65

    Default

    Quote Originally Posted by tezza View Post
    It just may be a reflection of a USA monitor being matched up with non-USA machines.
    Hi Tez,

    I think it's a even more fundamental. I think it has to do with that fact that the monitor is designed for 60Hz power. Even though you have corrected for the input voltage, it is still only 50Hz. Therefore, the sync rates in the monitor are now off from what they should be. The color carrier of the International NTSC motherboard maybe at 3.58MHz, but the monitor no longer decodes at that frequency, since the line frequency is slower than by design.

    I know I read about this somewhere in the long past, but I can't remember where or I would direct you to it. If anyone can verify or refute this, please speak up.

    Dutch

  5. #5

    Default

    Yes, that sounds totally plausible and is probably the problem.

    If it is, I guess the next question is, is there a simple fix i.e. a component that can be changed (a crystal?) which fixes the sync rates. Anyone know?

    I suspect just a component switch would be too simple. If not, I'll just keep it as a monochrome spare.

    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

    Quote Originally Posted by Dutch View Post
    I think it's a even more fundamental. I think it has to do with that fact that the monitor is designed for 60Hz power. Even though you have corrected for the input voltage, it is still only 50Hz. Therefore, the sync rates in the monitor are now off from what they should be. The color carrier of the International NTSC motherboard maybe at 3.58MHz, but the monitor no longer decodes at that frequency, since the line frequency is slower than by design.

    I know I read about this somewhere in the long past, but I can't remember where or I would direct you to it. If anyone can verify or refute this, please speak up.
    Vintage TVs used to have the refresh rate synched to the line voltage frequency, but at least with NTSC sets, that hasn't been the case since the 1950s, when color TV was introduced and the refresh rate was changed from exactly 60 Hz down to 59.94 Hz. Most of the time this gets specified as simply "60 Hz" (or 30 frames per second), but even today in digital video media, the NTSC video standard is officially 59.94 Hz (or 29.97 frames per second).

    Also, remember that when it enters a computer or monitor, the first thing that happens to the incoming AC household voltage is that it is converted to DC power at various voltages (5 and 12 volts in the computer, and around 20,000 volts for the CRT flyback in the monitor!). At that point, the AC line frequency becomes irrelevant since it has been converted to DC.

    Color TV synched to the AC line frequency would be pretty much unusuable anyway, since the line frequency constantly varies slightly due to system demand, such as this meter in the UK measures:

    http://www.dynamicdemand.co.uk/grid.htm

  7. #7

    Default

    Hmm..ok,

    So a U.S. monitor should show colours on my Apples then?

    Must be some other issue then.

    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)


  8. #8
    Join Date
    Jan 2008
    Location
    Clifton Park, NY
    Posts
    180

    Default

    This is probably too simple, but worth mentioning. What about the pushbutton that selects between color and monochrome? Perhaps the contact is dirty or broken and the monitor is stuck in monochrome mode. You could try actuating it repeatedly and use some contact cleaner. Or, disassemble the monitor and check its functionality. If the monitor in question is the same model as the one displayed with your platinum on your website then I'm 99% sure it has this button.
    Last edited by bugman2112; March 1st, 2010 at 04:57 AM.

  9. #9

    Default

    Hi
    I just looked it up.
    Pal uses a color burst frequency of 4.43361875 MHz
    and ntsc uses 3.579545 MHz.
    Completely different.
    Dwight

  10. #10

    Default

    Quote Originally Posted by bugman2112 View Post
    This is probably too simple, but worth mentioning. What about the pushbutton that selects between color and monochrome? Perhaps the contact is dirty or broken and the monitor is stuck in monochrome mode. You could try actuating it repeatedly and use some contact cleaner. Or, disassemble the monitor and check its functionality. If the monitor in question is the same model as the one displayed with your platinum on your website then I'm 99% sure it has this button.
    Yes, I thought of this too. Although the switch makes a firm click, this is the first thing I would check out if I open the case. I just want to make siure it's not a NTSC vrs PAL thing first before I open it up.

    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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