27 Oct
2013
27 Oct
'13
12:14 p.m.
> Are you sure it's the light pen header?
The IBM CGA card has 2 header
> plugs on it, one fo the a light pen, the other for a modulator. The
> composite signal goes ot the latter.
On Fri, 25 Oct 2013, Philip Andrews
wrote:
There is a very good possibility I got the two
mixed up looking at the
board. They aren't labeled.
In the "early" days of MDA and CGA, "EVERY" video board had a 6 pin
light 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
Yes. FWIW, it was also used to connect to the monitor in the IBM5155
'Portable PC' whcih was a Zenith composite-input unit.
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.
A number of CGA boards with no RCA sockets put the composite signal on
the otherwise unsed pin 7 of the DE9 socket.
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
What's wrong with calling them 'monochrome' monitors?
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.
Agreed. As I mentioned, the internal monitor of the 5155 was a composite
RS170 monitor. The stnadard mode on that was 80 column text, it was
perfectly readable.
However, I've not seen a TV, even a b&w TV [1] which gives useable 80
column text when fed via an RF modulator.
[1] I think 'black and white' is correct here. No sane manufactuer [2]
ever made a monochrome TV wherte hte phosphor was anything other than
white.
[2] OK,jsut after WW2 in the UK there were verious homebuilt TVs using
ex-radar CRTs, often VCR97s [3] These gave a green and black image. But
no commercial TVs, AFAIK, used them. There was asid to have been a product
in the UK consisting of a piece of transparent plastic film with a blue
band at the top, ink i nthe middle nad green at the bottom. You put it
over a B&W TV screen and got blue sky, green grass and flesh-coloured
people. Well, that was the idea. Needless to say it was useless....
[3] The same CRT as was used for the Willimas tube store.
-tony