Compaq CGA card, schematics?

On Fri, 25 Oct 2013, Philip Andrews wrote: In the "early" days of MDA and CGA, "EVERY" video board had a 6 pin light pen connector. The boards that had that AND a 4 pin (composite and power) connector were CGA. THAT was how you identified the boards! The 4 pin connector is the same as that on an Apple ][. It has composite video, power, ground, and often a removed pin for keying. The Sup'R'ModII RF modulator was made for those, and was, for a time, the most popular, for that reason. It was on channel 33? (UHF), whereas most RF modulators of the time were channel 3 or 4 (VHF). To tune a TV for use with the Sup'R'Mod modulator, you found the 24 hour speed freak preacher man, and tweaked the channel knob half a notch to the left. The SupRMod also had RCA input connector, so for the very rare CGA compatible boards that did not include an RCA connector, it could be used to take the 4 pin output of the video board, and use its other input as an RCA output for composite monitors. The Compaq CGA (and EGA) boards ALSO had a 2 x 6? connector mid-board for the internal monitor. The Compaq boards were also recognizable, because their mounting bracket had an extra 90 degree bend. Later, Compaq apparently stopped using those special brackets. Color NTSC composite monitors were barely/almost readable in 80 column modes with ANY video source. B&W NTSC composite monitors (disunirregardless of phosphor color - refusal to let them be called "black and white" if they are green or orange is nothing more than attempt to avoid communication), are readable and usable in 80 column modes. Yes, they are NOT as pretty, nice, comfortable to use as the MDA monitors, but calling them unreadable is an exaggeration either to avoid communication, or to get an employer to provide a comfortable display. CGA was 640x200 pixels, so the 80x25 characters were 5x7, within 8x8 box. MDA was 720x348 pixels, so the 80x25 pixels were 9x12. That is certainly a significant difference for a higher quality, and even "more ergonomic" display, but NOT justification to call 5x7 characters "unreadable", unless that is the specific exaggeration needed to get an employer to upgrade. If they ARE unreadable, the fault is with using a monitor that is inadequate to display 80 columns, NOT the video board. Note that the Compaq internal monitor was EGA capable, so there was also an EGA video board available (and an add-on from ATI for one of their EGA cards to make it into a Compaq board!), and the video on that internal monitor is going to look WAY better than composite output to a color monitor or TV. If you add an RF modulator in between, in order to display on the old Philco in the living room, you will have a signal degraded to below acceptable. -- Grumpy Ol' Fred cisin at xenosoft.com