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Conference 7.286::atarist

Title:Atari ST, TT, & Falcon
Notice:Please read note 1.0 and its replies before posting!
Moderator:FUNYET::ANDERSON
Created:Mon Apr 04 1988
Last Modified:Tue May 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1433
Total number of notes:10312

580.0. "DIY monochrome monitor?" by JUMBLY::BLUNN () Wed Aug 30 1989 15:58

    it seems that atari's mono monitor is more expensive than other
    mono monitors.
    
    it may have been suggested before, but couldn't you get an
    ordinary mono monitor and wind up its line & field generators.
    
    in the uk, straight tv frequency monitors run at 15.625khz
    and 50hz.
    to my knowledge the atari mono monitor runs at 35.7khz and
    70hz.
    surely one or two minor component changes could accomplish
    the necessary change.
    
    has anyone done this? is it possible?
    
    thanks
    
    bill
T.RTitleUserPersonal
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580.1No way Jose !!MGOI03::CSCHMIDTScio, Me Nil ScireThu Aug 31 1989 15:2532
    That's not an easy task at all !!
    
    You have to know that the 15kHz or 37.5kHz are signals that eventually
    deflect the electron beam in your CRT (Cathode Ray Tube) by way
    of electrical currents. You need fairly hefty currents anyways and
    the deflection coils would prevent you from going over a certain
    frequency in a normal TV monitor.
    
    Additionally, that small frequency of 50 or 70 Hz is quite important
    also to watch. That's the frequency with which the picture gets
    updated - only with a TV the beam writes only every second line
    of one half of a picture, then skips to the top and writes the rest
    of the picture. The beam does that skipping 50 times a second, but
    the actual picture changes only 25 times a second.
    Confused now ?
    Anyways, the picture update frequency is most important in
    considerations for ergonomical computer design.
    In Europe the general rule now is to have more than 70 Hz , because
    only these frequencies seem to have no adverse side effects on the
    person using the equipment. (like stress, headache ...)
    
    To top it all off, the higher your line frequency and your update
    frequency, the higher will be the necessary video bandwidth because
    that is the mathematical product of the two - and that is directly
    related to the cost of the monitor.
    
    So, in my opinion the Atari SM124 is a very good product for the
    price - a TV monitor with the same features would be much more
    expensive.
    
    But your question was whether you could do one yourself - the answer
    is no, unless youre very experienced in electronics.