gla@cbnewsj.cb.att.com (gregory.l.allen) (04/25/91)
My father has an AT&T 6300. He has disabled the indigenous video card and has
used other CGA video cards successfully. I recently acquired a true Blue
original IBM CGA card (full-card) because it is the only source of <<color>>
composite output that we could find for a reasonable price. However, when
we use the composite output to his Magnavox RGB monitor, we get only black &
white output. The monitor works fine with a different 9-pin CGA card.
A technician in California suggested that the "colorburst
frequency" needed to be adjusted on the "motherboard" to adjust the setup
to give color.
I have two questions that someone may be able to help us with:
1) is there anything else that needs to be done to use an IBM CGA card in a
6300 (do we need a bus corrector, etc.?)
2) I thought the colorburst frequency would be generated by a crystal. Can
this be adjusted, and if so, how and where?
We need color composite output to generate a TV signal for a VCR. We are
making titles for home videotapes. If anyone has suggestions on doing this
we would also be grateful. Thanks for any and all information.
Greg Allen gla@moss.emsp.att.com WH 2a-110 (201)386-7404dale@cec2.wustl.edu (Dale Frye) (05/03/91)
In article <1710010@hpcc01.HP.COM> drudman@hpcc01.HP.COM (Drew Rudman) writes: >As far as I know, the composite port on ANY CGA card supplies only a black and >white signal (it samples off of the intensity signal of the CGA.) No CGA card >I know of (and I used to sell all kinds - new and used) will provide you with >a color composite signal. WRONG! I've hooked the composite video jack to a composite video color monitor and (thru a modulator) to a color tv. At 640x200 certain color combonations don't work very well but there is most definitely color. This was with a true-blue IBM CGA card. The reason people think it's only B&W is because most people use that jack to hook up a cheap monochrome display. Dale Frye Washington University in St. Louis P.S. Come to think about it, when IBM first demo'ed the PC here (1982) they had the CGA hooked to a Sony tv through the video jack.
eh1b+@andrew.cmu.edu (Eric David Hornchek) (05/03/91)
I got a CGA card from Jameco or JDR a couple of years ago. It has both a monochrome and color composite output jack. Even if connected to the color jack, the monitor will only display color in the LOW RESOLUTION modes (ie 320x200 and 40 column text). High resolution and 80column text are always displayed in monochrome due to the resolution incababilitys of composite monitors. There is a potentiometer at the front of my AT mother board that I also needed to adjust in order to get correct color output. There may or may not be such a pot on your PC.
tj@gpu.utcs.utoronto.ca (Terry Jones) (05/03/91)
As has been pointed out, the CGA composite is colour, but it should also be added that You may not see colour unless the motherboard clock is exactly correct. The 3.579 colourburst signal is tied to the clock signal fet to the board somehow (don't ask me, this is just my experience). I had to adjust the tiny trim cap on the MOTHERBOARD to get colours.