5 Nov
2007
5 Nov
'07
5:46 a.m.
Eventually I'll be shipping various 8-bit machines to the US, and was thinking
of using a PC with a TV card as a display (most of the machines have UK PAL RF
outputs, and I could add modulators to the ones that don't).
However:
- All TV card software I've seen has been utter crap, when it even works
at all.
- Typically there seems to be no scaling of the picture to fill the PC
screen.
- There's an obvious quality drop in the RF stages.
- I'm warned that the digital tuners in TV cards often have problems
locking on to the weaker signal produced by home micros.
So... how about hooking straight to the TTL RGB outputs of the vintage
machines and somehow sampling lines of data into the PC for display in a
window (with appropriate scaling in software as/when necessary so that the
image more or less fills the PC display)?
Surely someone's homebrewed something like this already? I presume the speeds
at which things need to work can be pretty high - but in theory it's just an
RGB framegrabber but without all the analogue-type circuitry needed to decode
a picture?
I'm planning on shipping a few TTL RGB displays to the US, but maintaining
them is going to be more difficult than maintaining the machines (and I
imagine there are all sorts of pitfalls in taking a US-designed TTL RGB
display and trying to use it with a UK-designed micro, as the frequencies
involved won't be quite the same)
thoughts welcome...
Jules
5 Nov
5 Nov
7:15 a.m.
Eventually I'll be shipping various 8-bit machines
to the US, and was
thinking
of using a PC with a TV card as a display (most of the machines have UK
PAL RF
outputs, and I could add modulators to the ones that don't).
However:
- All TV card software I've seen has been utter crap, when it even works
at all.
- Typically there seems to be no scaling of the picture to fill the PC
screen.
- There's an obvious quality drop in the RF stages.
- I'm warned that the digital tuners in TV cards often have problems
locking on to the weaker signal produced by home micros.
So... how about hooking straight to the TTL RGB outputs of the vintage
machines and somehow sampling lines of data into the PC for display in a
window (with appropriate scaling in software as/when necessary so that the
image more or less fills the PC display)?
Surely someone's homebrewed something like this already? I presume the speeds
at which things need to work can be pretty high - but in theory it's just an
RGB framegrabber but without all the analogue-type circuitry needed to decode
a picture?
I'm planning on shipping a few TTL RGB displays to the US, but maintaining
them is going to be more difficult than maintaining the machines (and I
imagine there are all sorts of pitfalls in taking a US-designed TTL RGB
display and trying to use it with a UK-designed micro, as the frequencies
involved won't be quite the same)
thoughts welcome...
Jules
Hi,
First, have you tried Linux with tvtime and a boring old analogue BT878
capture card? There will always be quality loss when transmitting over RF
so if you don't want that then it's probably best to seek something else.
Also does it have to be attached to a PC? You could try adapting the RGB
output to a PC VGA monitor directly.
From the minimal research I've done the VGA
standard appears to use 1Vp-p
RGB signals terminated to a 75 ohm load. So to convert
from TTL RGB to VGA
it should be something like this (hope you use a fixed font!):
O +5v
|
\
/
\ 300R
/
\
|
|\ |
Luminance| \ 51R |
O-| >----/\/\/\/----o
| / |
|/ 7405 |
|
|\ |
R/G/B | \ 27R |
0-| >----/\/\/\/----o------------O VGA Out terminated
| / | to 75 ohms.
|/ \
/ 100R
7405 \
(OC non- /
inverting) \
|
|
-----
---
-
Whew. Good to brush up on Ohm's law. What this might produce is a voltage
of approximately 0.7V when both inputs are high, 0.5V when the Luminance
input is low, and about 0.2V when the R/G/B input is low, when terminated
into 75 ohms... maybe.
If you blow up a nice monitor I assume no responsibility. Also I have not
tested this at all :)
If you copy this circuit three times for the R, G and B outputs you should
be able to wire it up to a VGA monitor. But now we need sync. Do your
vintage computers have two lines for sync? One for horizontal and one for
vertical? Or is it some sort of combination or even sync-on-green?
Cheers,
Alexis.
7:49 a.m.
Hiya,
First, have you tried Linux with tvtime and a boring
old analogue BT878
capture card?
I think I've tried three different BT878-based TV cards in Linux - I've only
ever got one of them to semi-work (despite them working in Windows - albeit at
awful quality and in a tiny little window on the desktop that makes them next
to useless anyway). That's against a TV signal too - I've heard from several
sources that TV cards have a real problem with the modulators used in typical
8-bit micros (UM1233 etc.)
The Linux code for TV cards seems to be something on an undocumented mess :-(
It seems like a lot of unnecessary complexity to go TTL->composite->RF and
then back to digital again, too.
Also does it have to be attached to a PC? You could
try adapting the RGB
output to a PC VGA monitor directly.
No, I don't need a PC. I just need *something* in the US that can cope with
typical UK-style picture formats (typically 'home' micros in the UK will be
designed around PAL signals at 625 lines interlaced I expect, whereas I expect
US micros of the 80s were geared more toward NTSC displays of 525 lines)
I'm not sure if VGA will cope either - I don't think a typical VGA monitor
will sync down to the frequencies involved (i.e. converting TTL to the
necessary 'analogue' RGB of VGA is the easy bit :-)
Oh, sync lines on the machines I've got are typically composite, so some sort
of sync separator would be needed too...
This just strikes me as the sort of project that people will have done before,
because monitors take up lots of space and because there's not a lot of sense
in going from a digital source to analogue and then back to digital again.
cheers
Jules
5:47 p.m.
On 05/11/2007 12:49, Jules Richardson wrote:
No, I don't need a PC. I just need *something* in
the US that can cope
with typical UK-style picture formats (typically 'home' micros in the UK
will be designed around PAL signals at 625 lines interlaced I expect,
whereas I expect US micros of the 80s were geared more toward NTSC
displays of 525 lines)
I'm not sure if VGA will cope either - I don't think a typical VGA
monitor will sync down to the frequencies involved (i.e. converting TTL
to the necessary 'analogue' RGB of VGA is the easy bit :-)
It's a pity you didn't ask this yesterday when you were here: I could
have shown you my workshop monitor. It's an Acorn AKF53 connected to an
ordinary 4-way KVM switch (only the Video part used) to which, in turn,
are connected a BBC B's RGB output, a PC's VGA card, an Archimedes, and
something else (usually). All work.
I can't remember what modes an AKF12 or ADF32 support, but if one of
them is similar to my AKF53, that's your choice. If it works for a
Beeb, it should work for other machines that have similar RGB outputs.
Alexis' idea about the circuit should work too. His surmise about 1V
pk-pk for VGA is correct; I've used a similar circuit to do exactly
that, and something not too distant to combine all the signals to make
composite video (I could have shown you the ISA card for that too,
though it only uses the ISA bus to get power). If you need to merge
hsync and vsync, a simple XOR gate (1/4 of an LS86, for example) will do
well, but often you can get away with just combining them, wire-or
style, possibly with a couple of small-signal diodes. Some monitors
don't mind the hsync disappearing from the composite signal during the
vsync pulse; others prefer it to be present (inverted, if you use an XOR).
Have you tried any flat-screen monitors? Some of them are designed to
work as TV displays, and will handle horizontal rates in the 15kHz range
as well as signals in the VGA (etc) ranges.
--
Pete Peter Turnbull
Network Manager
University of York
6:31 p.m.
Pete Turnbull wrote:
On 05/11/2007 12:49, Jules Richardson wrote:
Heh - oops :-) I'm thinking that taking monitors overseas with me isn't much
of a long-term solution though; they'll fail eventually and patching them up
US-side is less than ideal.
Having a gadget available that's either readily obtainable within the US or
easily buildable seems like a better long-term solution; it's just a question
of whether the slight (typical) frequency differences / screen geometries
between the two markets are going to cause a problem in finding something that
works off the shelf.
No, I don't need a PC. I just need
*something* in the US that can cope
with typical UK-style picture formats (typically 'home' micros in the
UK will be designed around PAL signals at 625 lines interlaced I
expect, whereas I expect US micros of the 80s were geared more toward
NTSC displays of 525 lines)
I'm not sure if VGA will cope either - I don't think a typical VGA
monitor will sync down to the frequencies involved (i.e. converting
TTL to the necessary 'analogue' RGB of VGA is the easy bit :-)
It's a pity you didn't ask this yesterday when you were here: I could
have shown you my workshop monitor. Alexis' idea about the circuit should work too.
His surmise about 1V
pk-pk for VGA is correct
I didn't think many VGA displays would sync down to the frequencies used by
the older kit, though?
I've used a similar circuit to do exactly
that, and something not too distant to combine all the signals to make
composite video (I could have shown you the ISA card for that too,
though it only uses the ISA bus to get power). If you need to merge
hsync and vsync, a simple XOR gate (1/4 of an LS86, for example) will do
well, but often you can get away with just combining them, wire-or
style, possibly with a couple of small-signal diodes.
Yep, I've done the LS86 'trick' before for combining syncs - but lots of the
old kit I have outputs composite sync, and for driving something like VGA I
expect I'll need separate syncs. Of course I suspect I can tap into them
somewhere within the circuitry of whatever system's hooked up to the display
(ISTR that splitting a composite sync signal is a bit complicated, but it's
been a while)
Have you tried any flat-screen monitors? Some of them
are designed to
work as TV displays, and will handle horizontal rates in the 15kHz range
as well as signals in the VGA (etc) ranges.
Hmm, I've not tried that. The 19" Hercules LCD I have might work I suppose
(and it's so awful for normal work that it's getting dumped for a good
old-fashioned CRT soon as I get my stuff across the pond anyway)
cheers
Jules
8:04 p.m.
Jules Richardson wrote:
Hiya,
What would happen if you used one of the video cards that has
the video in/out jacks and setup to input PAL video? Most of
those cards have quite a few options as to how they treat the
video. I haven't tried it but I would expect it to receive PAL
format video input and display a usable picture on the PC screen.
First, have you tried Linux with tvtime and a
boring old analogue BT878
capture card?
I think I've tried three different BT878-based TV cards in Linux - I've
only ever got one of them to semi-work (despite them working in Windows
- albeit at awful quality and in a tiny little window on the desktop
that makes them next to useless anyway). That's against a TV signal too
- I've heard from several sources that TV cards have a real problem with
the modulators used in typical 8-bit micros (UM1233 etc.)
The Linux code for TV cards seems to be something on an undocumented
mess :-(
It seems like a lot of unnecessary complexity to go TTL->composite->RF
and then back to digital again, too.
Also does it have to be attached to a PC? You
could try adapting the RGB
output to a PC VGA monitor directly.
No, I don't need a PC. I just need *something* in the US that can cope
with typical UK-style picture formats (typically 'home' micros in the UK
will be designed around PAL signals at 625 lines interlaced I expect,
whereas I expect US micros of the 80s were geared more toward NTSC
displays of 525 lines)
I'm not sure if VGA will cope either - I don't think a typical VGA
monitor will sync down to the frequencies involved (i.e. converting TTL
to the necessary 'analogue' RGB of VGA is the easy bit :-)
Oh, sync lines on the machines I've got are typically composite, so some
sort of sync separator would be needed too...
This just strikes me as the sort of project that people will have done
before, because monitors take up lots of space and because there's not a
lot of sense in going from a digital source to analogue and then back to
digital again.
cheers
Jules
.
4:59 p.m.
On Monday 05 November 2007 07:15, Alexis wrote:
RGB signals terminated to a 75 ohm load. So to convert
from TTL RGB to VGA
it should be something like this (hope you use a fixed font!):
(Snip)
7405 \
(OC non- /
inverting) \
Uh, the 7405 is an inverting gate...
Maybe the 7407 would be what you were thinking of?
http://www.classiccmp.org/rtellason/by-generic-number.html
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
5 Nov
5 Nov
6:39 p.m.
Jules Richardson wrote:
So... how about hooking straight to the TTL RGB outputs of the vintage
machines and somehow sampling lines of data into the PC for display in a
window (with appropriate scaling in software as/when necessary so that
the image more or less fills the PC display)?
Video capture of 9-pin TTL RGB (such as that used by IBM CGA, Commodore
C64, etc.) is something that I have been trying to do for a very long
time, without appreciable success. I even tracked down an old scan
converter that claimed to convert TTL RGB to NTSC so I could grab it
with a capture card turned out to not work (although it's possible the
scan converter was broken).
I ordered a Video Turtle in 2001 which was supposed to do this same type
of conversion but it never worked and the company disappeared before I
could get tech support.
If anyone comes up with a solution that costs less than $200, I'd love
to hear it.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
7:31 p.m.
An old (CGA/MDA/EGA/VGA) monitor will do the trick. Years ago a
friend from the UK sent me a bunch of PAL VHS tapes with loads of old
British Comedy and other local interest stuff--and a VHS player.
I replaced the power transformer in the player and picked up a kit
that demodulated PAL to RGB. I still play it back occasionally
through my old Mitsubishi Diamondscan Multisync. I've also used an
old Sony Multiscan and an early NEC Multisync. None so much as
flickered.
Parenthetically, through this exercise I did realize how much better
PAL was than NTSC. The color balance was always excellent from the
tapes, particularly as compared to the way off-the-air NTSC looks.
A favorite game of mine was to walk into one of the big box
electronics stores such as Circuit City and say to the guy flogging
big-screen sets from an acre of glowing boxes, "They all look
different. Which one has the correct colors?"
Cheers,
Chuck
8:10 p.m.
Chuck Guzis wrote:
Parenthetically, through this exercise I did realize
how much better
PAL was than NTSC. The color balance was always excellent from the
tapes, particularly as compared to the way off-the-air NTSC looks.
Yes, but the flickering (50Hz) is annoying if you haven't been nursed on
NTSC (60Hz). It took me months of viewing PAL (I was mastering a PAL
DVD) before I got used to it.
Resolution and color are indeed better than NTSC.
A favorite game of mine was to walk into one of the
big box
electronics stores such as Circuit City and say to the guy flogging
big-screen sets from an acre of glowing boxes, "They all look
different. Which one has the correct colors?"
None of them. Seriously. One of the dirty little secrets of that
industry is that the "default" or "standard" settings for
color/tint/brightness/contrast/sharpness is that they are calibrated for
the store show room, NOT a regular home setting. All the colors are
oversaturated, the sharpness is artificially high, etc. Every friend I
know who purchases a new TV find me knocking on their door a few days
later with my Digital Video Essentials calibration DVD.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
8:43 p.m.
Jim Leonard wrote:
None of them. Seriously. One of the dirty little
secrets of that
industry is that the "default" or "standard" settings for
color/tint/brightness/contrast/sharpness is that they are calibrated for
the store show room, NOT a regular home setting. All the colors are
oversaturated, the sharpness is artificially high, etc. Every friend I
know who purchases a new TV find me knocking on their door a few days
later with my Digital Video Essentials calibration DVD.
I allways turn down Saturation about 20%, the rest I tend to leave the same.
I wish TV's had a GAMMA button rather than brightness/contrast. :(
Ben
7 Nov
7 Nov
6:26 p.m.
On Nov 5, 2007 3:39 PM, Jim Leonard <trixter at oldskool.org> wrote:
Jules Richardson wrote:
I've had luck with converting the RGB to VGA and then converting the
VGA to NTSC using both this sort of device
(http://www.genao.com/converters.htm) and this
(http://www.converters.tv/products/cga_to_vga/425.html (Warning,
expensive))
Not cheap, but when it needs to be done, it needs to be done.
converters.tv does have a CGA to NTSC converter that they are offering
for 110 AUD (~$100 US)
(http://www.converters.tv/signals/cga_to_ntsc.html)
Eric
So... how about hooking straight to the TTL RGB outputs of the vintage
machines and somehow sampling lines of data into the PC for display in a
window (with appropriate scaling in software as/when necessary so that
the image more or less fills the PC display)?
Video capture of 9-pin TTL RGB (such as that used by IBM CGA, Commodore
C64, etc.) is something that I have been trying to do for a very long
time, without appreciable success. I even tracked down an old scan
converter that claimed to convert TTL RGB to NTSC so I could grab it
with a capture card turned out to not work (although it's possible the
scan converter was broken).
8:53 p.m.
Eric J Korpela wrote:
I've had luck with converting the RGB to VGA and
then converting the
VGA to NTSC using both this sort of device
(http://www.genao.com/converters.htm) and this
(http://www.converters.tv/products/cga_to_vga/425.html (Warning,
expensive))
Not cheap, but when it needs to be done, it needs to be done.
converters.tv does have a CGA to NTSC converter that they are offering
for 110 AUD (~$100 US)
(http://www.converters.tv/signals/cga_to_ntsc.html)
Unfortunately both the converters.tv units ignore the "intensity" pin of
CGA, which means that only 8 of the 16 colors can be displayed from an
IBM CGA card. :-( This is the bit (pun intended) missing from all
converters I've come across, unfortunately.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
8 Nov
8 Nov
6:18 a.m.
Eric J Korpela wrote:
There's a line of chip from Analog Devices, AD273/AD274/AD275 and others,
which will convert from RGB to NTSC/PAL. It gives composite and split video
outputs. They're in the US$5 range. Perhaps this could be used with my
previous circuit that converts TTL to analogue?
Alexis.
I've had luck with converting the RGB to VGA
and then converting the
VGA to NTSC using both this sort of device
(http://www.genao.com/converters.htm) and this
(http://www.converters.tv/products/cga_to_vga/425.html (Warning,
expensive))
Not cheap, but when it needs to be done, it needs to be done.
converters.tv does have a CGA to NTSC converter that they are offering
for 110 AUD (~$100 US)
(http://www.converters.tv/signals/cga_to_ntsc.html)
Unfortunately both the converters.tv units ignore the "intensity" pin of
CGA, which means that only 8 of the 16 colors can be displayed from an
IBM CGA card. :-( This is the bit (pun intended) missing from all
converters I've come across, unfortunately.
16 Nov
16 Nov
12:02 a.m.
Alexis wrote:
There's a line of chip from Analog Devices,
AD273/AD274/AD275 and others,
which will convert from RGB to NTSC/PAL. It gives composite and split video
outputs. They're in the US$5 range. Perhaps this could be used with my
previous circuit that converts TTL to analogue?
Possibly, but I'm still not sure that it would handle the intensity bit
of CGA (RGBI).
I have ordered an Extron which should convert TTL to analog and also
split it out to R/G/B/H (vertical sync on green). From there I hope to
connect it to a scan converter that claims to go down to 15Khz horizontal.
I'm still not crossing my fingers for all 16 colors though.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
4:44 a.m.
On Thu, 2007-11-15 at 23:02 -0600, Jim Leonard wrote:
Alexis wrote:
We made a bodge cable for RGBI to analogue RGB. It's just some
resistors, really.
Gordon
There's a line of chip from Analog Devices,
AD273/AD274/AD275 and others,
which will convert from RGB to NTSC/PAL. It gives composite and split video
outputs. They're in the US$5 range. Perhaps this could be used with my
previous circuit that converts TTL to analogue?
Possibly, but I'm still not sure that it would handle the intensity bit
of CGA (RGBI). 
3:08 p.m.
--- Gordon JC Pearce <gordonjcp at gjcp.net> wrote:
On Thu, 2007-11-15 at 23:02 -0600, Jim Leonard
wrote:
handle the intensity bit
Not likely the intensity bit was handled then. Yes
it's seemingly no problem to convert ttl levels to
ntsc or whatever.
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Alexis wrote:
> There's a line of chip from Analog Devices,
AD273/AD274/AD275 and
others,
> which will convert from RGB to NTSC/PAL. It
gives composite and split video
> outputs. They're in the US$5 range.
Perhaps this
could be used with my
previous
circuit that converts TTL to analogue?
Possibly, but I'm still not sure that it would of CGA (RGBI).
We made a bodge cable for RGBI to analogue RGB.
It's just some
resistors, really.
6:50 p.m.
Gordon JC Pearce wrote:
On Thu, 2007-11-15 at 23:02 -0600, Jim Leonard wrote:
What was the pinout/schematics of such a cable? How did you handle the
intensity bit?
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
Alexis wrote:
We made a bodge cable for RGBI to analogue RGB. It's just some
resistors, really. There's a line of chip from Analog Devices,
AD273/AD274/AD275 and others,
which will convert from RGB to NTSC/PAL. It gives composite and split video
outputs. They're in the US$5 range. Perhaps this could be used with my
previous circuit that converts TTL to analogue?
Possibly, but I'm still not
sure that it would handle the intensity bit
of CGA (RGBI).
17 Nov
17 Nov
5:22 a.m.
On Fri, 2007-11-16 at 17:50 -0600, Jim Leonard wrote:
Gordon JC Pearce wrote:
On Thu, 2007-11-15 at 23:02 -0600, Jim Leonard
wrote:
What was the pinout/schematics of such a cable? How did you handle the
intensity bit? Alexis wrote:
We made a bodge cable for RGBI to analogue RGB. It's just some
resistors, really. There's a line of chip from Analog Devices,
AD273/AD274/AD275 and others,
which will convert from RGB to NTSC/PAL. It gives composite and split video
outputs. They're in the US$5 range. Perhaps this could be used with my
previous circuit that converts TTL to analogue?
Possibly, but I'm still not
sure that it would handle the intensity bit
of CGA (RGBI). From memory, and it was a while ago, we had three
voltage dividers to
knock the TTL outputs down to .7v, and then three more resistors
from
the intensity bit to the analogue outputs.
There may have been some diodes there.
The sync combiner was a couple of resistors and a transistor.
Gordon
10:35 a.m.
--- Gordon JC Pearce <gordonjcp at gjcp.net> wrote:
I used to combine h and v syncs to green with only a
resistor (somewhat but not entirely related I guess).
Don't ask me what the value was though. As I recall it
wasn't terribly crucial though.
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What was the
pinout/schematics of such a cable?
How did you handle the
intensity bit?
From memory, and it was a while ago, we had three
voltage dividers to
knock the TTL outputs down to .7v, and then three
more resistors from
the intensity bit to the analogue outputs.
There may have been some diodes there.
The sync combiner was a couple of resistors and a
transistor.
1:46 p.m.
On 17 Nov 2007 at 10:22, Gordon JC Pearce wrote:
It can also be done with a 74LS06 OC inverter and a few resistors. A
fancy version might use a '221 one shot to adjust sync pulse position
and width. I think the one I used to drive an RGB monitor with SOG
From memory,
and it was a while ago, we had three voltage dividers to
knock the TTL outputs down
to .7v, and then three more resistors from
the intensity bit to the analogue outputs.
There may have been some diodes there.
The sync combiner was a couple of resistors and a transistor. from a VGA output used a 74HC86 XOR and was
self-powered.
Cheers,
Chuck
2:28 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 17 Nov 2007 at 10:22, Gordon JC Pearce wrote:
what would be nice if there was an area for the group
to act as a *scratch pad*. So some of this stuff could
go down *on paper*. Thoughts?...
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>From memory, and it was a while ago, we had
three
voltage dividers to
knock the TTL outputs down to .7v, and then three
more resistors from
the intensity bit to the analogue outputs.
There may have been some diodes there.
The sync combiner was a couple of resistors and a
transistor.
It can also be done with a 74LS06 OC inverter and a
few resistors. A
fancy version might use a '221 one shot to adjust
sync pulse position
and width. I think the one I used to drive an RGB
monitor with SOG
from a VGA output used a 74HC86 XOR and was
self-powered. 
7:45 p.m.
Chris M wrote:
--- Chuck Guzis <cclist at sydex.com> wrote:
Something like this?
http://www.classiccmp.org/kb/
Doc
On 17 Nov 2007 at 10:22, Gordon JC Pearce wrote:
what would be nice if there was an area for the group
to act as a *scratch pad*. So some of this stuff could
go down *on paper*. Thoughts?... >From memory, and it was a while ago, we had
three
voltage dividers to
knock the TTL outputs down to .7v, and then three
more resistors from
the intensity bit to the analogue outputs.
There may have been some diodes there.
The sync combiner was a couple of resistors and a
transistor.
It can also be done with a 74LS06 OC inverter and a
few resistors. A
fancy version might use a '221 one shot to adjust
sync pulse position
and width. I think the one I used to drive an RGB
monitor with SOG
from a VGA output used a 74HC86 XOR and was
self-powered.
9:11 p.m.
On Nov 16, 2007 4:48 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I don't think I ever owned a CGA monitor that got brown correct.
I'm just cheap that way.
Eric
We made a
bodge cable for RGBI to analogue RGB. It's just some
resistors, really.
Unless you want to get the brown colour correct :-)
17 Nov
17 Nov
10:33 a.m.
--- Eric J Korpela <korpela at ssl.berkeley.edu> wrote:
On Nov 16, 2007 4:48 PM, Tony Duell
<ard at p850ug1.demon.co.uk> wrote:
:-)
I don't think I ever owned a CGA monitor that got
brown correct.
I was going to say isn't that largely dependent on
the monitor used? A non-issue w/a newer analogue
monitor, that is if the voltage was correct. But you
could always vary the resistance on that particular
line, no?
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> We made a bodge cable for RGBI to analogue
RGB.
It's just some
resistors, really.
Unless you want to get the brown colour correct
1:40 p.m.
On 17 Nov 2007 at 7:33, Chris M wrote:
I was going to say isn't that largely dependent
on
the monitor used? A non-issue w/a newer analogue
monitor, that is if the voltage was correct. But you
could always vary the resistance on that particular
line, no?
We've been here before. The IBM color display as well as the EGA
version contains a PROM to correct the "dark yellow" color to brown.
It was duplicated on few, if any third-party units.
Cheers,
Chuck
2:26 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 17 Nov 2007 at 7:33, Chris M wrote:
I know. I was there. It was just after I joined the
list. And it was I, even I, who pointed out that there
was a game written by Bill Gates w/a big brown donkey,
putting to rest the doubts of the naysayers.
Off the top of my head, I don't know, or rather can't
see what a prom had to do with it. If a monitor's
phosphors were capable of producing brown (presumably
all were) and the unit is *tuned* to take a *brown*
signal and display brown, you'd have brown. But I
guess I'll have to look over those posts (~2.5 years
ago IIRC).
Yeah I guess the original IBM 5153 display stood out
in at least that respect. But it was pretty
unspectacular in other respects. The colors were
*deep* enough, which usually depended on the
*darkness* of the tube. But the dot pitch wasn't
anything particularly unusual. I have a nice one in my
attic. Got to dig it out this week when I have a few
days to play...
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I was going to say isn't that largely
dependent
on
the monitor used? A non-issue w/a newer analogue
monitor, that is if the voltage was correct. But
you
could always vary the resistance on that
particular
line, no?
We've been here before. The IBM color display as
well as the EGA
version contains a PROM to correct the "dark yellow"
color to brown.
It was duplicated on few, if any third-party units.
4:53 p.m.
On 17 Nov 2007 at 11:26, Chris M wrote:
Off the top of my head, I don't know, or rather
can't
see what a prom had to do with it. If a monitor's
phosphors were capable of producing brown (presumably
all were) and the unit is *tuned* to take a *brown*
signal and display brown, you'd have brown. But I
guess I'll have to look over those posts (~2.5 years
ago IIRC).
The EGA had the prom; without consulting my O&A for the CGA version,
it might have been some TTL logic rather than a ROM. The situation
goes this way. If rgb are "normal level" red, green and blue signals
and RGB is "intensified", dark yellow is r+g; brown is r+1/2g and
bright yellow is RG. To get brown, you need logic in the monitor to
drop the green level to one-half "normal" brightness only when the
brown combination is detected. Otheriwse, if you simply tune down
the green level by half for all colors, everything suffers.
Cheers,
Chuck
5:16 p.m.
We've been here before. The IBM color display as
well as the EGA
version contains a PROM to correct the "dark yellow" color to brown.
Minor correction. While the 5154 EGA monitor uses a PROM for this, the
5153 CGA monitor does it all in simple TTL chips (including wire-ANDed
open-collector stuff)
It was duplicated on few, if any third-party units.
Perhaops I only deal with the better units, but the Philips service
manual I've just looked at gets it right, and the very nice Trinitron
TTL/analogue monitor that I use with Beebs and Torch XXXes has the
circuitry too.
-tony
18 Nov
18 Nov
1:08 a.m.
Tony Duell wrote:
the very nice Trinitron
TTL/analogue monitor
A trinitron TTL monitor!! I had no idea such beasts existed! You've
just named my next Holy Grail to find.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
1:47 a.m.
On 18 Nov 2007 at 0:08, Jim Leonard wrote:
A trinitron TTL monitor!! I had no idea such beasts
existed! You've
just named my next Holy Grail to find.
They weren't that hard to find. My first EGA monitor was a Sony CPD-
1302 multiscan (I may even have the service docs for it somewhere).
It would actually do both TTL and analogue (selectable by a switch in
the rear). CGA, MDA and EGA and lesser VGA, as well as serve as a
Mac display. Had the usual shadows from the damper wires, but
otherwise a good sharp display--and not bad for the money at the
time. I had two of them and both were working after 10 years of hard
use when I gave them away.
Cheers,
Chuck
2:02 a.m.
Chuck Guzis wrote:
They weren't that hard to find. My first EGA
monitor was a Sony CPD-
Key word here being "weren't". They sure are hard to find *now*. I
don't know where this list finds these miracle recyclers, but I am in
the chicagoland suburbs and every goodwill, computer recycler, etc.
simply doesn't have this neat stuff. Jason T. has been diligent in
combing through the local Craigslist but I am relegated to pawing
through the remains of Bell
Labs^H^H^H^H^H^H^H^H^HLucent^H^H^H^H^H^HAlcatel-Lucent's
Naperville/Lisle campus buildings, where I am currently employed.
(And before anyway asks, I can't remove stuff off-campus, sorry. But
it's not that interesting -- mostly common Sparc 20/Ultra-5 parts and
various non-trinitron monitors.)
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
1:27 p.m.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 18 Nov 2007 at 0:08, Jim Leonard wrote:
That doesn't count! Once NEC released the Multisync,
everyone started copying it.
IIRC the Sony was the first to do 800 x 600 SEGA/VGA.
The Multisync II only went to 800 x 560 technically.
It probably could do 600 lines, funny I can't
remember, but it was a strain in all likelihood. weeeeeeeeeeee
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A trinitron TTL monitor!! I had no idea such
beasts existed! You've
just named my next Holy Grail to find.
They weren't that hard to find. My first EGA
monitor was a Sony CPD-
1302 multiscan (I may even have the service docs for
it somewhere).
It would actually do both TTL and analogue
(selectable by a switch in
the rear).
1:48 p.m.
On 18 Nov 2007 at 10:27, Chris M wrote:
IIRC, when scan rates were changed on the Sony, there was a bunch of
"clickety-click" of relays that you didn't hear with the NECs. My
12" Mitsubishi Diamond Scan is completely silent when changing scan
rates.
Cheers,
Chuck
That
doesn't count! Once NEC released the Multisync,
everyone started copying it.
2:17 p.m.
when my Multisync II (NEC) was new, you'd here 1
click. Over the years it would say click 3 times.
Occasionally it would click loads of times, like a
scaled down anti-aircraft weapon.
--- Chuck Guzis <cclist at sydex.com> wrote:
On 18 Nov 2007 at 10:27, Chris M wrote:
____________________________________________________________________________________
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Make Yahoo! your homepage.
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> That doesn't count! Once NEC released
the
Multisync,
everyone started copying it.
IIRC, when scan rates were changed on the Sony,
there was a bunch of
"clickety-click" of relays that you didn't hear with
the NECs. My
12" Mitsubishi Diamond Scan is completely silent
when changing scan
rates.
Cheers,
Chuck
5:16 p.m.
Tony Duell wrote:
The unit I have is badged 'Torch', who were a company who started off
selling add-ons for the BBC micro (including second processors) and then
made somewhat odd unix machines with a graphical front end, like the XXX.
The monitor is clearly a Sony chassis, although the input connector is
proabably Torch. It's an 8-pin DIN socket, 2 of the pins of which go to a
piezo buzzer in the monitor. This socket is mounted on a little PCB that
is then connected to a header plug on one of the PCBs of the monitor.
The chassis is 3 main PCBs (PSU, deflection, video) with a couple of
daughterboards. Being a SOny, there are some very helpful annotations on
the silkscreen, including things like the CRT pinout. It's one of the
older Trinitron CRTs with the coaxial EHT connector for horizontal static
convergernce adjustment.
Vey nicely made and easy to keep going :-)
-tony
the very nice Trinitron
TTL/analogue monitor
A trinitron TTL monitor!! I had no idea such beasts existed! You've
just named my next Holy Grail to find.
1:07 a.m.
Chuck Guzis wrote:
We've been here before. The IBM color display as
well as the EGA
version contains a PROM to correct the "dark yellow" color to brown.
It was duplicated on few, if any third-party units.
It wasn't a PROM, just circuitry. Some more details here (from the
thread last year): http://www.oldskool.org/pc/cgacal
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
17 Nov
17 Nov
5:12 p.m.
I don't
think I ever owned a CGA monitor that got
brown correct.
I was going to say isn't that largely dependent on
the monitor used? A non-issue w/a newer analogue
monitor, that is if the voltage was correct. But you
could always vary the resistance on that particular
line, no?
12 Nov
12 Nov
2:22 p.m.
On Nov 7, 2007 5:53 PM, Jim Leonard <trixter at oldskool.org> wrote:
Unfortunately both the converters.tv units ignore the
"intensity" pin of
CGA, which means that only 8 of the 16 colors can be displayed from an
IBM CGA card. :-( This is the bit (pun intended) missing from all
converters I've come across, unfortunately.
I forgot about that. Many (if not all) of these boards are actually
converting analog signal levels rather than digital. The most common
use of these boards is vintage video games, which were often analog
RGB at CGA (i.e. video) scan rates. You can usually recover the
intensity bit with a small preconditioner board. If you are using
multiple sources on one of these boards you are going to want to
precondition the signal levels anyway rather than having to fiddle
with the gain every time you change sources. A quad line driver, some
resistors and capacitors should do the trick if you want quality. If
you want simple (no power supply required) and are willing to live
with some imprecision in color output you can skip the line driver .
http://www.softwolves.pp.se/cbm/maskinvara/scart.en.html
Eric
5 Nov
5 Nov
6:55 p.m.
Eventually I'll be shipping various 8-bit machines to the US, and was thinking
of using a PC with a TV card as a display (most of the machines have UK PAL RF
outputs, and I could add modulators to the ones that don't).
However:
- All TV card software I've seen has been utter crap, when it even works
at all.
- Typically there seems to be no scaling of the picture to fill the PC
screen.
- There's an obvious quality drop in the RF stages.
- I'm warned that the digital tuners in TV cards often have problems
locking on to the weaker signal produced by home micros.
I am sure I've seen vido capture devices with USB interfaces on the
computer side and a composite or S-video input on the other side. Using
one of those would avoid the loss in quility from the modulator and any
problems with the TV tuner side of things, but wouldn't be as good as
takinmg th RGB signals drectly.
So... how about hooking straight to the TTL RGB outputs of the vintage
machines and somehow sampling lines of data into the PC for display in a
window (with appropriate scaling in software as/when necessary so that the
image more or less fills the PC display)?
Surely someone's homebrewed something like this already? I presume the speeds
at which things need to work can be pretty high - but in theory it's just an
Most _home_ computers (as opposed to workstations) have a dot clock under
16MHz. Not that high by modern stadnards.
RGB framegrabber but without all the analogue-type
circuitry needed to decode
a picture?
I'm planning on shipping a few TTL RGB displays to the US, but maintaining
them is going to be more difficult than maintaining the machines (and I
It shouldn't be that hard...
imagine there are all sorts of pitfalls in taking a
US-designed TTL RGB
display and trying to use it with a UK-designed micro, as the frequencies
involved won't be quite the same)
The horizontal frequencies are much the same on UK and US TVs (15625Hz
.vs. 15770Hz). I doubt there exists a monitor that can lock to one and
can't be tweaked to lock to the other. Modifying the vertical deflection
circuit is a lot easier in general, sinxe (1) it's a lot slower and (2)
it doesn't have other functions, like EHT generation, hung off it.
Having done the reverse many times (used US machines with UK monitors) I
doubt it'll be much of a prolem.
-tony
8:04 p.m.
--- Tony Duell <ard at p850ug1.demon.co.uk> wrote:
The horizontal frequencies are much the same on UK
and US TVs (15625Hz
.vs. 15770Hz). I doubt there exists a monitor that
can lock to one and
can't be tweaked to lock to the other. Modifying the
vertical deflection
circuit is a lot easier in general, sinxe (1) it's a
lot slower and (2)
it doesn't have other functions, like EHT
generation, hung off it.
Having done the reverse many times (used US machines
with UK monitors) I
doubt it'll be much of a prolem.
It's really that simple? I have some PAL (presumably)
units on their way here from OZ. I'd be elated to find
out that all I'd need to do is tweak the monitor.
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6 Nov
6 Nov
3:15 a.m.
On 06/11/2007 01:04, Chris M wrote:
--- Tony Duell <ard at p850ug1.demon.co.uk>
wrote:
> The horizontal frequencies are much the same on UK
> and US TVs (15625Hz .vs. 15770Hz).
It's really that simple? I have some PAL
(presumably)
units on their way here from OZ. I'd be elated to find
out that all I'd need to do is tweak the monitor.
Apart from colour, yes. If you're using RGB or composite mono, it's
quite likely to just work, possibly with a little verticla and
horizontal hold tweaking. If you're using NTSC or PAL composite colour,
you'll get monochrome if you use the wrong monitor.
--
Pete Peter Turnbull
Network Manager
University of York
4:21 p.m.
It's really that simple? I have some PAL
(presumably)
units on their way here from OZ. I'd be elated to find
out that all I'd need to do is tweak the monitor.
For monochrome composite video, or separate RGB (wheter TTL or analogue),
then yes, all you should beed to do is tweak the monitor. The horizontal
frequencies are close enough that it will proabably sync anyway, if not,
then a touch on the horizontal frequncy control (maybe an inductor) will
do it. The vertical hold control will probably need re-adjusting, but
that's all.
Of course if the units output PAL colour composite video it's a bit
harder. Feeding that into an NTSC monitor (even after the above tweaks)
will get you monochrom output. I've seen NTSC-PAL converters (simple
colour system converters, they don't change the scan rates), I assume the
reverse exist too. Maybe that would do the trick.
If you have the origianl PAL monitors, it should be easy to get them to
work on different mains voltages. AFAIK no small monitor cares about
mains freqeuncy, the vertical deflection is not locked to the mains or
anything like that.
-tony
7 Nov
7 Nov
6:07 p.m.
--- Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Curious where I'd put the inductor...
It's
really that simple? I have some PAL
(presumably)
units on their way here from OZ. I'd be
elated to
find
out that all I'd need to do is tweak the
monitor.
For monochrome composite video, or separate RGB
(wheter TTL or analogue),
then yes, all you should beed to do is tweak the
monitor. The horizontal
frequencies are close enough that it will proabably
sync anyway, if not,
then a touch on the horizontal frequncy control
(maybe an inductor) will
do it. The vertical hold control will probably need
re-adjusting, but
that's all. Of course if the units output PAL colour composite
video it's a bit
harder. Feeding that into an NTSC monitor (even
after the above tweaks)
will get you monochrom output. I've seen NTSC-PAL
converters (simple
colour system converters, they don't change the scan
rates), I assume the
reverse exist too. Maybe that would do the trick.
These are presumably composite color PAL units
(Australia). Have any idea what would go into a
PAL-NTSC converter (how many (roughly) and what type
of components)? I'm just curious how complicated
something like that would be to construct.
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7:28 p.m.
For monochrome
composite video, or separate RGB
(wheter TTL or analogue),
then yes, all you should beed to do is tweak the
monitor. The horizontal
frequencies are close enough that it will proabably
sync anyway, if not,
then a touch on the horizontal frequncy control
(maybe an inductor) will
do it. The vertical hold control will probably need
re-adjusting, but
that's all.
Curious where I'd put the inductor...
These are presumably composite color PAL units
(Australia). Have any idea what would go into a
If you feed that into an NTSC composite monitor and tweak the vertical
frequency, you should get a good _monochrome_ pictore.
PAL-NTSC converter (how many (roughly) and what type
of components)? I'm just curious how complicated
something like that would be to construct.
Normally you decode the PAL signal to RGB (or at least to the YUV
signals) and re-encode as NTSC. If you do the first part, you might as well
display the RGB sigals directly, assuming you can find some way to get
your monitor to accemt them.
The decoder is not that complciated if you use the ICs used in older TV
sets (perhaps 3 or 4 chips, cryutal, maybe a delay line, lots of
passives). Setting it up can in interesting the first tiem (I speak from
expeirence). It's not something I'd recomnend tryign to build unless you
have some expeirence with video circuitry.
-tony
8:38 p.m.
Hi,
These are presumably composite color PAL units
(Australia). Have any idea what would go into a
PAL-NTSC converter (how many (roughly) and what
type of components)?
I vaguely recall from my Apple ][ days, that at least the early
(pre-Europlus?) machines were NTSC only. To use them in Europe we had to fit
an Apple NTSC->PAL converter card into one of the expansion slots.
It wasn't a perfect conversion, but was "good enough".
I'm wondering whether the circuit could be modified to convert PAL->NTSC for
this application. I remember seeing the circuit diagram in one of the
machines' user manuals, so it's probably online somewhere.
TTFN - Pete.
8 Nov
8 Nov
7:32 p.m.
--- Ensor <classiccmp at memory-alpha.org.uk> wrote:
Hi,
Right this occurred to me. It seems to me it would
make much more sense to modify some passive components
(I would assume) inside the box instead of hacking
some kind of converter together. But maybe you're
right, they'll be NTSC out of the box.
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These are presumably composite color PAL units
(Australia). Have any idea what would go into a
PAL-NTSC converter (how many (roughly) and what
type of components)?
I vaguely recall from my Apple ][ days, that at
least the early
(pre-Europlus?) machines were NTSC only. To use them
in Europe we had to fit
an Apple NTSC->PAL converter card into one of the
expansion slots.
It wasn't a perfect conversion, but was "good
enough".
I'm wondering whether the circuit could be modified
to convert PAL->NTSC for
this application. I remember seeing the circuit
diagram in one of the
machines' user manuals, so it's probably online
somewhere.
5 Nov
5 Nov
6:56 p.m.
now you know what would be real nice...
hows about a way of sampling a video signal somehow
and piping onto a USB 2.0 port. 480mbps IIRC, and the
fastest dot clocks of old digital cards is around
25mhz, again IIRC. So on paper at least it's feasible.
Then you can display it on a laptop screen. Complex no
doubt, and then there's the s/w element. Whatever.
There was a discussion on a similar note earlier this
year. Some had said that certain LCD monitors
(TV-monitors?) would sync down to TV frequencies
(obviously if it was designed for broadcast signals).
If this is so, you'd still need voltage conversion
(TTL -> analong).
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7:13 p.m.
now you know what would be real nice...
hows about a way of sampling a video signal somehow
and piping onto a USB 2.0 port.
This sounds like a video capture dongle on steroids, frankly. I would
be surprised if such a device didn't already exist.
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
-- Never explain, never apologise. -- John Arbuthnot "Jackie" Fisher ----------
8:05 p.m.
Cameron Kaiser wrote:
They *do* exist, as cheap as $30 -- for VGA. Not TTL RGB (most likely
due to obvious lack of demand).
They don't pipe raw video, though; it's always compressed, usually
MPEG-2 or MPEG-4 depending on how expensive and new a device you
purchase. This is because reaching maximum USB speeds is rarely
achieved on typical (read: poor) chipset implementation of USB on cheap
PCs. The video is compressed down to something manageable, like
9mbit/s. This means even a USB 1.x port can take it.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
now you know
what would be real nice...
hows about a way of sampling a video signal somehow
and piping onto a USB 2.0 port.
This sounds like a video capture dongle on steroids, frankly. I would
be surprised if such a device didn't already exist.
6092
days inactive
6105
days old
52 comments
16 participants
participants (16)
-
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
cclist＠sydex.com -
chrism3667＠yahoo.com -
cisin＠xenosoft.com -
classiccmp＠memory-alpha.org.uk -
doc＠mdrconsult.com -
gordonjcp＠gjcp.net -
john＠guntersville.net -
julesrichardsonuk＠yahoo.co.uk -
korpela＠ssl.berkeley.edu -
pete＠dunnington.plus.com -
rtellason＠verizon.net -
spectre＠floodgap.com -
thrashbarg＠kaput.homeunix.org -
trixter＠oldskool.org