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Message #675 in area AMY_TECH
From: Brian Jack                                         Sent 
To:   All                                                Thu  1 Jul 92 23:24
Subj: High Resolution C64 Monitor trick for Amiga Video

Noramally, running an Amiga on a commodore 64 monitor through the NTSC
(external video port) gives a hard-to-read high resolution display.

A good fix for this problem is to use the Luminence/Chromanence signals
instead of the regular NTSC signal.  This modification needs only a few cheap
devices if they aren't already available:

   An A520 video adapter      $50.00   (If you're using your Amiga with
                                        a C64 monitor you probably already
                                        have one.)

   Two RCA video cables       $8.00    (You only need one if you are already 
                                         using a C64 monitor as you already  
                                          have one of the two required cables)

How to do it:

  Find the MONO jack on the back of the Amiga 500, over by the RGB port that
the A520 should be plugged into.  Use one of your cables and place one end
into the MONO jack and the other into LUMA on the C64 monitor.

  Now use your other (or existing) cable and put it not into the EXTERNAL
VIDEO, but rather, into the CHROMA slot and the monitor.

  All that's left now, is to flip the switch from external to C64 and you
will now have a high-resolution color display.  The color may be a bit dim. 
Turn the color up with the color knob and counter adjust with the brightness
(back control not the front control) to minimize the dark purple ghost image.
 There will be a bit of ghosting, as the A520 doesn't produce a 100%
unadulterated CHROMA signal.  You will notice, however, that the afterimage
is dark and has virtually no effect on clarity once the controls are set
right.  My five-year old 1802 has no trouble producing sharp text that rivals
Amiga monitors even in hi-res (not, however, interlaced, that is still a
problem.  I use a green screen for my interlace work and live with the
flicker an color interlaced displayes).  Even with the small drawbacks, this
trick can save a lot of money (the cost of a new Amiga Monitor) for C64 users
who have or are upgrading to Amigas.

                                             - Briguy


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