24 Oct
2013
24 Oct
'13
1:19 p.m.
Dave,
If the internal screen is fine then the syncs are at
or close to the
proper frequency, so any problems are going to be around the NTSC
modulator, which would be fun to debug without a scope...
I do have a scope- poking about down in the chassis is difficult- I don't have
an ISA extension card. The composite trace drops down to the back side of the
card, comes up through a resistor, goes to the light-pen header, through another
resistor and vanishes into the middle layer. I could start just prodding with my
meter to see where it re-surfaces... but, well, yeah. A schematic would make
that easier.
The image on composite "tears" horizontally. I made a video of it, hooked up to
my TV set in the living room: http://youtu.be/a4jcKiSwUos
On the other hand whilst I have never tried the
Composite on CGA, but I
have tried comparable modes on several other computers, including my
rather old Atari STE, and a very modern Raspberry PI and it sounds like
its working (almost) just fine. The composite out on CGA cards always
was pretty useless, and "legible, just" pretty much describes any
80-colum output on composite. Try 40 a column mode (2 or 3)...
That's in 40-col mode, above. In 80-col it goes into a text mode rather like
MDA, which I haven't scoped to see if it's not present at the jack, or if the TV
refuses to display it. It's remarkably crisp, considering.
On a regular TV set (older, cheaper, no-name set)-
http://www.flickr.com/photos/philandrews/8657681921/
Above was trying to display this-
http://www.flickr.com/photos/philandrews/8660917851/
Admittedly that was all unbalanced, but I'm sure it should be a little better
than that.
(Oh and my experience is with PAL, NTSC would
probably be worse.....)
If you have a TV with a SCART then the circuit below would work..
http://www.electroschematics.com/377/
but I guess you are in the US and and your TV will have CYMG inputs.
Actually that circuit would probably work with CYMG but the colours
would be wrong.
Yeah, I should have said. I moved out here to the States a number
of years ago
now. My TV sets have all the usual "modern" inputs for here, CATV (NTSC
modulated), Composite-in, YPbPr component, HDMI and the one in the bedroom has a
VGA-in.
If have a modern LCD TV with a VGA input you could try
something
similar, but leaving the syncs separate and feed it into the VGA. This
might sound daft but often LCD TVs will sync to normal TV on the VGA. IT
doesn't work with monitors, but it does with some TVs. As a quick and
dirty test you could just use 470 ohms on all leads and omit the "I"
line....
I can give that a try, but it's a band-aid to the symptom. I've got another
machine with CGA out and the TV displays it nicely. I'd like to be able to use
the composite-out because the machine has several games on that make use of the
timing inconsistencies in NTSC to create a larger color palette than the
standard 4. That would, however, be useful for other applications. It's been a
while since I've seen a SCART connector..!
Dave
--
Dave Wade G4UGM
Illegitimi Non Carborundum
25 Oct
25 Oct
12:35 a.m.
On 24/10/2013 21:19, phil at viscom.net wrote:
That does look nasty. Looks like a level is out some where so might be a
cap died or a resistor gone out of tolerence.
If you can scope the video might be worth looking at a line and trying
to see whats wrong. How is the NTSC modulation performed, is there a
chip or is it disrcete?
Also might be worth spending a little time googling the part number
101340-001 but I can't find a schematic.
Apparently looking at the "service guide" that is controlled
by jumpers
on the card.
http://www.old-computers.com/museum/docs.asp?c=547&st=1
but if thats the service guide and it doesn't even show the chip legend
I think find a schematic is unlikely. In fact might be worth posting here:-
http://www.old-computers.com/museum/computer.asp?c=547&st=1
and seeing what you get..
--
Dave Wade G4UGM
Illegitimi Non Carborundum
Dave,
Sorry this is short, just off to work...
If the
internal screen is fine then the syncs are at or close to the
proper frequency, so any problems are going to be around the NTSC
modulator, which would be fun to debug without a scope...
I do have a scope-
poking about down in the chassis is difficult- I don't have
an ISA extension card. The composite trace drops down to the back side of the
card, comes up through a resistor, goes to the light-pen header, through another
resistor and vanishes into the middle layer. I could start just prodding with my
meter to see where it re-surfaces... but, well, yeah. A schematic would make
that easier.
The image on composite "tears" horizontally. I made a video of it, hooked up
to
my TV set in the living room: http://youtu.be/a4jcKiSwUos On the other
hand whilst I have never tried the Composite on CGA, but I
have tried comparable modes on several other computers, including my
rather old Atari STE, and a very modern Raspberry PI and it sounds like
its working (almost) just fine. The composite out on CGA cards always
was pretty useless, and "legible, just" pretty much describes any
80-colum output on composite. Try 40 a column mode (2 or 3)...
That's in
40-col mode, above. In 80-col it goes into a text mode rather like
MDA, which I haven't scoped to see if it's not present at the jack, or if the TV
refuses to display it. It's remarkably crisp, considering.
On a regular TV set (older, cheaper, no-name set)-
http://www.flickr.com/photos/philandrews/8657681921/
Above was trying to display this-
http://www.flickr.com/photos/philandrews/8660917851/
Admittedly that was all unbalanced, but I'm sure it should be a little better
than that. (Oh and my
experience is with PAL, NTSC would probably be worse.....)
If you have a TV with a SCART then the circuit below would work..
http://www.electroschematics.com/377/
but I guess you are in the US and and your TV will have CYMG inputs.
Actually that circuit would probably work with CYMG but the colours
would be wrong.
Yeah, I should have said. I moved out here to the States a number
of years ago
now. My TV sets have all the usual "modern" inputs for here, CATV (NTSC
modulated), Composite-in, YPbPr component, HDMI and the one in the bedroom has a
VGA-in.
If have a modern LCD TV with a VGA input you
could try something
similar, but leaving the syncs separate and feed it into the VGA. This
might sound daft but often LCD TVs will sync to normal TV on the VGA. IT
doesn't work with monitors, but it does with some TVs. As a quick and
dirty test you could just use 470 ohms on all leads and omit the "I"
line....
I can give that a try, but it's a band-aid to the symptom. I've
got another
machine with CGA out and the TV displays it nicely. I'd like to be able to use
the composite-out because the machine has several games on that make use of the
timing inconsistencies in NTSC to create a larger color palette than the
standard 4. That would, however, be useful for other applications. It's been a
while since I've seen a SCART connector..!
Dave
--
Dave Wade G4UGM
Illegitimi Non Carborundum
2:08 p.m.
Dave,
A trick there is to solder short wires onto the points you want to
monitor, plug the card in, and then probe the free ends of the wires. But
this is only useful if you know what points are likely to be of interest,
which you presumably don't
If the internal screen is fine then the syncs are
at or close to the
proper frequency, so any problems are going to be around the NTSC
modulator, which would be fun to debug without a scope...
I do have a scope- poking about down in the chassis is difficult- I don't have
an ISA extension card. The composite trace drops down to the back side of the card, comes up through a resistor, goes to the
light-pen header, through another
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.
resistor and vanishes into the middle layer. I could
start just prodding with my
meter to see where it re-surfaces... but, well, yeah. A schematic would make
that easier.
Have you looked at the IBM CGA card scehamtic? Could any of it match up?
The compostie video circuit for the IBM CGA card consists of :
A shift register (1.5 'S74) to produce the various pahses of the subcarrier
A 'LS151 mux ot select the corect phase based on the colour to display
4 buffers (half a 'LS244) to buffer the following 4 signals : Composite
sync *which is not simply the sync signals from the 6845, there;s quite a
bit of logic in the way, however this logic is also used for the outptus
on the DE9 socket, the compoite sync signal is effectively the XNOR of
those 2 outputs) ; blanking ; intensity (I bit); and the output of the mux
The outputs of those buffers go to a resistor netowrk to produce the
composite signal
Which is then buffered by a 2N3904 emitter follower.
There are no capacitors in the signal path on the IBM card.
Assuming the Compaq card did work correctly at one time (this is not
_certain_ of course), it would appear the fault must be around the
reistor network/emitter follower stage (assuming that's what was used).
Tracing that out shouln't be too hard.
-tony
3:12 p.m.
On 10/25/13 4:08 PM, Tony Duell wrote:
A trick there is to solder short wires onto the points
you want to
monitor, plug the card in, and then probe the free ends of the wires.
But this is only useful if you know what points are likely to be of
interest, which you presumably don't
No, that was the object of asking.
Doesn't hurt to ask, I guess.
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.
There is a very good possibility I got the two
mixed up looking at the
board. They aren't labeled.
Have you looked at the IBM CGA card scehamtic? Could
any of it match
up? The compostie video circuit for the IBM CGA card consists of : A
shift register (1.5 'S74) to produce the various pahses of the
subcarrier A 'LS151 mux ot select the corect phase based on the colour
to display 4 buffers (half a 'LS244) to buffer the following 4 signals
: Composite sync *which is not simply the sync signals from the 6845,
there;s quite a bit of logic in the way, however this logic is also
used for the outptus on the DE9 socket, the compoite sync signal is
effectively the XNOR of those 2 outputs) ; blanking ; intensity (I
bit); and the output of the mux The outputs of those buffers go to a
resistor netowrk to produce the composite signal Which is then
buffered by a 2N3904 emitter follower. There are no capacitors in the
signal path on the IBM card. Assuming the Compaq card did work
correctly at one time (this is not _certain_ of course), it would
appear the fault must be around the reistor network/emitter follower
stage (assuming that's what was used). Tracing that out shouln't be
too hard. -tony
I hadn't looked at it per se- but, in looking for the chips you
mentioned and going over my pictures, I took a look at the settings on
my scope. I had scoped at 0.5V/div (I had dialed in and thought it was
on 1.0V/div), and the trace was 4 1/4 divisions high. Do the math... I
found the resistor that had gone short after that, and got the signal
back down to 1V p-p.
Net result:
http://www.flickr.com/photos/philandrews/10467625994/
Police Quest, even working properly in a multitude of pseudo-colors.
Sadly, I answered my own question and didn't notice!
Thanks for the help,
--Phil
26 Oct
26 Oct
4:28 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
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
5:17 p.m.
On 10/26/2013 5:28 PM, Fred Cisin wrote:
Did anyone ever USE a light pen?
--
> 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
pen connector. The boards that had that AND a 4 pin (composite and power)
connector were CGA. THAT was how you identified the boards! Grumpy Ol' Fred cisin at xenosoft.com
The other Ben.
6:03 p.m.
On Sat, 26 Oct 2013, ben wrote:
Did anyone ever USE a light pen?
Few.
Some (myself included) did so very briefly, just to try it.
And, the IBM MDA monitor had a long persistence phosphor (P39?) that
didn't work well with it.
For those with limited means, CGA, with an after-market composite B&W
monitor (of any color phosphor) was half the cost of any other video
system for 5150. Most of those would work well with light pens, but until
Windoze, there wasn't much demand for pointing devices.
Many people claimed that a mouse was "infinitely superior", but to them my
response was, "let me see you sign your name using a mouse." THAT was
usually an eye-opener.
--
Grumpy Ol' Fred cisin at xenosoft.com
7:35 p.m.
On 10/26/2013 06:03 PM, Fred Cisin wrote:
On Sat, 26 Oct 2013, ben wrote:
Same here, with a light pen (I still have) from some mainframe graphics
console (fat thing with a coiled cord and a fiber-optic tip). I used a
white (P4) CRT--better than the long-persistence green stuff,but the
accuracy, while good enough for selecting letters on a text display, was
totally unsuitable for fine tasks like drawing.
The clumsiness of the whole affair made me give it up fairly quickly.
--Chuck
Did anyone ever USE a light pen?
Few.
Some (myself included) did so very briefly, just to try it.
And, the IBM MDA monitor had a long persistence phosphor (P39?) that
didn't work well with it. 
8:04 p.m.
New subject: Promlink and DATA I/O 29b with Unipak 2 question...
Hi all,
Does anyone use Promlink with DATA I/O 29b with Unipak 2 (or a similar setup)?
I have a very simple question. How do I 'LOAD DATA FROM HOST'?
I have a serial connection to the programmer and I can program PROMs, but when I try to
read them I am told that the 'HOST PORT CANNOT BE THE SAME AS THE PROGRAMMER
PORT'
But I only have one serial port, and if I change things around then It doesn't work
because I'm trying to communicate through a port that is not connected to anything!!!
Is the serial link to the 29b only one way? My 29b has only one serial connector on the
back, but also a hole (presently covered) which looks like a place for another connector.
Do I need to somehow install another serial port on the 29b, or is there some setting that
I am overlooking?
Anyway, I'm confused. Any help would be greatly appreciated.
Phil
10:47 p.m.
New subject: Promlink and DATA I/O 29b with Unipak 2 question...
Ok...I think I figured it out.
I think should be selecting "LOAD RAM FROM MASTER" not 'LOAD DATA FROM
HOST'.
My bad.
Phil
On Oct 27, 2013, at 12:04 PM, Philip Lord <philip at neoncluster.com> wrote:
Hi all,
Does anyone use Promlink with DATA I/O 29b with Unipak 2 (or a similar setup)?
I have a very simple question. How do I 'LOAD DATA FROM HOST'?
I have a serial connection to the programmer and I can program PROMs, but when I try to
read them I am told that the 'HOST PORT CANNOT BE THE SAME AS THE PROGRAMMER
PORT'
But I only have one serial port, and if I change things around then It doesn't work
because I'm trying to communicate through a port that is not connected to anything!!!
Is the serial link to the 29b only one way? My 29b has only one serial connector on the
back, but also a hole (presently covered) which looks like a place for another connector.
Do I need to somehow install another serial port on the 29b, or is there some setting that
I am overlooking?
Anyway, I'm confused. Any help would be greatly appreciated.
Phil
27 Oct
27 Oct
12:20 p.m.
[IBM video cards and internal header connectors]
Did anyone ever USE a light pen?
Was there a commercial light pen that would connect to the IBM< CGA card?
Given that IBM seemed to use de facto standards for the connectors (the
composite heder on the CGA card being the same as the Apple ][, the
cassette connector on the 5150 being the same as the TRS-80), I wondered
if the light pen conenctor was also used elsewhere.
Howere were you supposed to route the light pen cable out of the system
unit case? There is no obvious hole for it.
Was there ever a lightpen for the PC-jr? I seem to remember a connector
for one on that machine.
-tony
2:35 p.m.
On 10/27/2013 12:20 PM, Tony Duell wrote:
Howere were you supposed to route the light pen cable
out of the system
unit case? There is no obvious hole for it.
In the 5150, there's a nice hole that has a filler plug in it right
above the keyboard/cassette DIN connectors. AFAIK, no specific use was
ever singled out for it.
I always wondered why RCA called the single-phosphor kinescopes
"monochorme", but didn't call the three-phosphor ones "polychrome"
or
"trichrome".
--Chuck
3:57 p.m.
> Howere were you supposed to route the light pen
cable out of the system
> unit case? There is no obvious hole for it.
On Sun, 27 Oct 2013, Chuck Guzis wrote:
In the 5150, there's a nice hole that has a filler
plug in it right
above the keyboard/cassette DIN connectors. AFAIK, no specific use was
ever singled out for it.
I have also seen that hole used for a power connector for external drive.
Some of the Compaq CGAs (back on topic, sorry.) had a notch in the edge
of the bracket for small flat cable (either 4 pin composite or light pen)
My first 5150 also had a blocked off d25 hole.
28 Oct
28 Oct
12:27 p.m.
On 10/27/2013 12:20 PM, Tony Duell wrote:
The 5160 and 5170 cases have that little blanking plate over the keyboard
connector. Perhaps that was a convenient hole to put the lightpen cable
through.
I do wonder why IBM didn't put the lightpen signals on a convenient
connector on the back fo the card, though. Jut abotu any use fo them
requires them to be connected to an external device.
Howere were you supposed to route the light pen
cable out of the system
unit case? There is no obvious hole for it.
In the 5150, there's a nice hole that has a filler plug in it right
above the keyboard/cassette DIN connectors. AFAIK, no specific use was
ever singled out for it.
I always wondered why RCA called the single-phosphor kinescopes
"monochorme", but didn't call the three-phosphor ones
"polychrome" or
"trichrome".
Given that 'chrome' == 'colour', I guess it's becuase a
single-phosphoe
CRT can only display one colour, albeit at various intensities. But due
to the chracteristics of the human eye, the 3-phosphor CRTs can display
just about any colour that you can see. So 'trichrome' would not really
be appropriate. 'Polychrome' would be OK, I guess.
-tony
27 Jan
27 Jan
12:24 p.m.
----- Original Message -----
From: "ben" <bfranchuk at jetnet.ab.ca>
To: <cctalk at classiccmp.org>
Sent: Sunday, October 27, 2013 12:17 AM
Subject: Re: Compaq CGA card, schematics?
I'm replying a little late to this (3 months late!), but to answer the
question: Yes!
I remember using a light pen in primary school as part of an educational
software package for the BBC Micro around 1986/7. We had to use it on a
transparent sheet which had vertical and horizontal coloured lines on it
(used by the light pen to detect the movement). Since then, I haven't ever
used one since - however I do own one for my Amiga :)
Regards,
Andrew B
aliensrcooluk at yahoo.co.uk
On 10/26/2013 5:28 PM, Fred Cisin wrote:
>>> 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
> pen connector. The boards that had that AND a 4
pin (composite and
power)
connector were
CGA. THAT was how you identified the boards!
Did anyone ever USE a light pen?
26 Oct
26 Oct
6:32 p.m.
On Sat, 26 Oct 2013, Fred Cisin wrote:
CGA was 640x200 pixels, so the 80x25 characters were
5x7, within 8x8 box.
MDA was 720x348 pixels, so the 80x25 pixels were 9x12.
CORRECTION: MDA (and hercules) was 720 x 350, NOT 348 (348 was
macintosh). MDA was text only, without pixel addressable graphics
capability - that was what Hercules exploited.
The Hercules card was a clone of the MDA, with the addition of pixel
addressable graphics. But Hercules was itself widely copied, and had lots
of nasty advertising around that, including at least one ad implying that
imitations of Hercules' board (which was unarguably a [slightly improved]
imitation of IBM's board) would destroy the computer and monitor.
27 Oct
27 Oct
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
1:49 p.m.
> 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
On Sun, 27 Oct 2013, Tony Duell wrote:
What's wrong with calling them
'monochrome' monitors?
"Monochrome NTSC composite" works.
But, in the days of the 5150, "monochrome monitor" with no other
clarifying adjectives was taken over [by the same people who gave us
"centronics connector", "quad density", and "DB9") to mean
monitors
compatible with MDA/Hercules.
And therefore, when the primary goal was to differentiate between RS170
single color V MDA compatible, "monochrome" was inappropriate.
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.
being the fault of the further degradation of conversion from composite to
RF, and then tuner conversion back. There was a previous implication in
this thread that composite couldn't do a readable 80 column.
[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....
OK for westerns, but not so good for interior shots, nor "Sea Hunt" style
glub-glub shows.
25 Oct
25 Oct
4:31 p.m.
On Fri, 25 Oct 2013, Tony Duell wrote:
yep
6 pin for light pen
4 pin for composite out
card, comes up
through a resistor, goes to the light-pen header, through another
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.
3747
days inactive
3842
days old
18 comments
8 participants
participants (8)
-
aliensrcooluk＠yahoo.co.uk -
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
cclist＠sydex.com -
cisin＠xenosoft.com -
dave.g4ugm＠gmail.com -
phil＠viscom.net -
philip＠neoncluster.com