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Convert RGsB to VGA

VSavic

New Member
Hello, everyone.
I have a cnc machine which have RGsB ( RGB sync on Green) output which is used as input for monitor screen.
I want to change currently used monitor with LCD monitor which have VGA connector as input.
Do you know how to build circuit which will convert RGsB output to VGA signal which I will use as input in LCD monitor?
 

ronsimpson

Well-Known Member
Most Helpful Member
We need to know more about your dead monitor. CGA, EGA, VGA?
Look at old LDC TVs. Many have RGB inputs and most likely will work. Many GVA monitors will not.
 
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rjenkinsgb

Well-Known Member
You should just be able to feed the green via a sync separator.

eg. the LM1881 is readily available, about $5.
Data here: http://www.ti.com/lit/ds/symlink/lm1881.pdf

That will give you sync, but not necessarily the right scan timing for VGA.

Or just buy a suitable LCD panel controller that includes analog RGB input - eg.


Edit - ps. If it's something like a Siemens 840C using BNC video outputs for RGB, look on the CPU board - there is likely a standard VGA socket as well..
Example: https://www.cofiem.fr/1226784-thickbox_default/siemens-6fc5110-0db02-0aa1.jpg
 
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dr pepper

Well-Known Member
Most Helpful Member
You'll need a multisync monitor, or one that is the same framerate as your machine.
 

rjenkinsgb

Well-Known Member
OK, it's using SMB coax connectors - I've never seen those use for video before.

Do you have access to an oscilloscope to see what the line and frame synch frequencies are, looking at the green video signal?
 

dr pepper

Well-Known Member
Most Helpful Member
I have a vax computer that has these:

119077

The video can have sort of a 'D' connector, but it had 3 seperate plugs.
It has a vero board with a Lm1881 on it feeding a Lcd monitor, doesnt work that well.
 

VSavic

New Member
I don't have an oscilloscope and I know that can be a problem. I suppose that synchronization is on green but I'm not 100% sure.
 

ronsimpson

Well-Known Member
Most Helpful Member
Most TVs and monitors look for separate sync first then drop back and look for sync on green.
I don't have an oscilloscope
We are trying to find what type of video you have. You can not tell us what the old monitor was. You can not make measurements on the video you have. This makes it hard. The picture does not have (PAL, SECAM, NTSC) formats. Each format has different timings. The speed of the video is different. That is why I suggested in post #2, getting a older LCD TV because many of those will work with many formats.
119116
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Most TVs and monitors look for separate sync first then drop back and look for sync on green.
I can't comment on monitors (although I'm extremely dubious), but certainly most (if not all?) TV's do no such thing.

But I fully agree with the rest, we're not been given any information at all, there's no way to make any suggestions other than blind guesses.
 

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