30 Jan
2005
30 Jan
'05
12:38 a.m.
does anyone happen to have a schematic for a simple circuit to extract
sync information from a sync-on-green video signal?
I've got a screen here I'd like to hook up to the Tek (I left the normal
monitor I use with the Tek at Bletchley), but it needs either seperate H
and V sync lines hooked up, or composite sync - it won't do sync on
green (which is all that the Tek provides).
I keep on finding sync combining circuits that'll do seperate sync to
sync on green everywhere, but nothing to do the reverse!
cheers
Jules
30 Jan
30 Jan
1 a.m.
On Sun, 2005-01-30 at 14:38, Jules Richardson wrote:
does anyone happen to have a schematic for a simple
circuit to extract
sync information from a sync-on-green video signal?
Maybe this will help, it also has a few useful links:
http://www.hut.fi/Misc/Electronics/faq/vga2rgb/scart.html
--
Lawrence Wilkinson lawrence(a)ljw.me.uk
Ph +44(0)1869-811059 http://www.ljw.me.uk
1:28 a.m.
On Sun, 30 Jan 2005 14:38:59 +0000
Jules Richardson <julesrichardsonuk(a)yahoo.co.uk> wrote:
does anyone happen to have a schematic for a simple
circuit to extract
sync information from a sync-on-green video signal?
The LM1881 IC is what you
need. Google will find data sheets and
application notes.
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
12:08 p.m.
I keep on finding sync combining circuits that'll
do seperate sync to
sync on green everywhere, but nothing to do the reverse!
I thought the right thing there was to simply connect the green output
to both the green video input and the sync input.
However, that's coming from someone who has never tried it (at least
not knowingly - I may have used adapters designed to do just that) and
who does not really understand the signals involved....
/~\ The ASCII der Mouse
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10:51 p.m.
On Sun, 2005-01-30 at 21:08 -0500, der Mouse wrote:
Yes, I expected that to work too, but no luck here with the Tek
connected to my old 19" Sun 'goldfish bowl' screen (which was working
when I last used it a few years ago)
Unfortunately I don't have an LM1881 chip in the spares pile :-( I could
have sworn there was an easier way though (i.e. not using a 'custom'
chip) but digging through my saved schematics I can't find anything.
The 21" Iiyama screen on my desktop PC has both BNC and VGA inputs and
will do S-O-G of course, so I can still hook the Tek up that way - but
the machine's noisy as all hell, so it would have been nice to get it
into another room with its own display (and just telnet in to work on
it)
cheers
Jules
I keep on
finding sync combining circuits that'll do seperate sync to
sync on green everywhere, but nothing to do the reverse!
I thought the right thing there was to simply connect the green output
to both the green video input and the sync input.
31 Jan
31 Jan
2:32 a.m.
On Mon, 31 Jan 2005 12:51:15 +0000
Jules Richardson <julesrichardsonuk(a)yahoo.co.uk> wrote:
Unfortunately I don't have an LM1881 chip in the
spares pile :-(
I could have sworn there was an easier way though
You can use an OPA wired as a
comparator too. Set the switch level to
about 0.15 V and you get C-sync out of the comparator. The black level
of a video signal is 0.3 V. Everything below down to 0 V is sync. You
should use a TTl IC behind the comparator as a line driver.
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
6:20 a.m.
Jules Richardson wrote (regarding sync separation):
Unfortunately I don't have an LM1881 chip in the
spares pile :-(
I could have sworn there was an easier way though
Jochen wrote:
You can use an OPA wired as a comparator too. Set the
switch level to
about 0.15 V and you get C-sync out of the comparator. The black level
of a video signal is 0.3 V. Everything below down to 0 V is sync. You
should use a TTl IC behind the comparator as a line driver.
Won't work reliably if the video is AC-coupled, which is *very* common.
The LM1881 (and the improved-spec EL4581) are designed to deal with
that.
7:49 a.m.
On Mon, 31 Jan 2005 12:20:53 -0800 (PST)
"Eric Smith" <eric(a)brouhaha.com> wrote:
Won't work reliably if the video is AC-coupled,
which is *very*
common.
I know. But I build a quick and dirty sync separator with a simple
comparator and it worked so well that I never got around to build a
proper sync separator based on a LM1881. :-)
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
2:34 a.m.
On Sun, 30 Jan 2005 21:08:52 -0500 (EST)
der Mouse <mouse(a)rodents.montreal.qc.ca> wrote:
I thought the right thing there was to simply connect
the green output
to both the green video input and the sync input.
Usualy the sync inputs are TTL
level. A video signal is sync from 0 to
0.3 V and black to white from 0.3 to 0.7 V.
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
4:11 a.m.
On Mon, 2005-01-31 at 02:08, der Mouse wrote:
that approach has worked for me before (connecting an SGI Indy to a
projector). YMMV, of course.
--
James F. Carter http://www.jfc.org.uk/
I keep on
finding sync combining circuits that'll do seperate sync to
sync on green everywhere, but nothing to do the reverse!
I thought the right thing there was to simply connect the green output
to both the green video input and the sync input. 
10:19 a.m.
On Sun, 30 Jan 2005 14:38:59 +0000, Jules Richardson
<julesrichardsonuk(a)yahoo.co.uk> wrote:
does anyone happen to have a schematic for a simple circuit to extract
sync information from a sync-on-green video signal?
I've got a screen here I'd like to hook up to the Tek (I left the normal
monitor I use with the Tek at Bletchley), but it needs either seperate H
and V sync lines hooked up, or composite sync - it won't do sync on
green (which is all that the Tek provides).
I keep on finding sync combining circuits that'll do seperate sync to
sync on green everywhere, but nothing to do the reverse!
cheers
Jules
I don't know if this is any help, but I bought a vga adaptor which has
both a male and female vga connector and converts sync-on-green both
ways. I will try and find the name of the company I bought ift from,
it was only about $45 including postage from the US.
It has worked for me using any combination of pc, sun. dec and sgi
monitors and machines. I have thrown at it.
Dan
10:19 a.m.
On Tue, 1 Feb 2005, Dan Williams wrote:
I don't know if this is any help, but I bought a
vga adaptor which has
both a male and female vga connector and converts sync-on-green both
ways. I will try and find the name of the company I bought ift from,
it was only about $45 including postage from the US.
It has worked for me using any combination of pc, sun. dec and sgi
monitors and machines. I have thrown at it.
If you find out where you got it from, i'd love to have one of these too
:)
alex/melt
7265
days inactive
7266
days old
11 comments
8 participants
participants (8)
-
eric＠brouhaha.com -
james＠jfc.org.uk -
jkunz＠unixag-kl.fh-kl.de -
julesrichardsonuk＠yahoo.co.uk -
ljw-cctech＠ljw.me.uk -
melt＠microvax.org -
mouse＠Rodents.Montreal.QC.CA -
williams.dan＠gmail.com