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HELP: Model 2 -> 15pin D-sub ->multisync (like m3)

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Sbdesign View Drop Down
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    Posted: 11 Jan 2019 at 1:50am
Hi,
Ive tested rally2 (model 3) using the vga style out connector to my multisync projector and it works (nearly)
ISSUE: not filling screen and input states 640x400 24khz 

Q: how do I get the 480 high?

MAIN ISSUE:

I assumed I could do this with model 2 (top skater)
I tried some wires I had about from the SR2 to lcd convertor, which had 5 wires to a vga block.
When I connected with a block those 5 wires to the 5 wires that come out of model 2, I get a picture but VERY high contrast.

The colour bar test was great for first 10-20%, but the remaining was all what should be on the last block.
Basically all mid colours 10%-90% were at 90% levels, making lots of white.  A bleached look but very darks still there.

I believe on model 3, the vga port is nothing special, and will only contain whats o the other socket RGBGS

So then I thought making a RGBGS to VGA, would be exactly what the model 3 filter board does?

Perhaps my wires are wrong?

I have looked at getting [url=https://www.ebay.co.uk/itm/Clever-Little-Box-CLB-VGAPCBUNIT-Solderless-VGA-PCB-Module/362460451781?hash=item54645393c5:g:-3kAAOSwetBbxiUn:rk:1:pf:1]EBAY LINK SOLDERLESS 15-pin]/URL]

but where do these 5 wires go? or is there another issue?





Edited by Sbdesign - 11 Jan 2019 at 1:50am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sbdesign Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 1:56am

not sure if this image on left (RGB) is what i would need?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 6:46am
Resolution wise, that’s already higher than model 2 (496x384) so it sounds like it’s got the wrong portion of the vertical image.

Are there potentiometers on the converter to adjust the input resistance for your contrast issue?
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sbdesign Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 7:40pm
Hi John,
The Resolution was the model 3 (didn't realise they were different)
should be 640x480 (4:3) but I get 640 x 400 :(

IM NOT using a convertor.  Thats my plan, as the projector is capable of 24khz.  I am trying to not use one, with one I can get it working, but colours and noise occur, which I don't believe can be reduced 100%.  Don't get me wrong, you can get them good, but just 100%

Because Model 3 works on the vga out I was hoping Model 2 would also.
BUT model 2 doesn't have VGA connector.



From my reading the CN6 and VGA are the same but different socket.

MODEL 3 (SEGA RALLY 2)
SO VGA to projector works 24khz
BUT CN6 to VGA to projector doesn't (too much white) 24khz

Which either means: my wiring to vga plug is wrong or the VGA port is different than the CN6

This is where I am stuck.

If I get this proven working, then this will also work on the model 2 that has no vga just CN6






Edited by Sbdesign - 11 Jan 2019 at 7:50pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gunblade Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 7:53pm
the signal on cn6 will be 3v whereas the signal on vga will be less than 1v

Edited by gunblade - 11 Jan 2019 at 7:55pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 8:06pm
Ah, it's not really 'VGA' (31kHz, 640x480) - just a 15-pin DSUB with a similar-to-VGA pinout (you see it on 15kHz stuff too). 
Model 3 is the same as Model2 - 24kHz, 496x384.

As gunblade points out, it's a difference in the signal amplitudes that makes the colours vary, so you could put in-line resistors to reduce the amplitude of the Model2 CN6 signal (they'll work in conjunction with the resistors in the monitor to act as a potential divider). Not sure what value, that's why potentiometers found in converter boards are useful.
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sbdesign Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 10:06pm
Thanks, will it need to variable resistor? 
Any idea what parts I should get to do this?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 10:25pm
I just said variable as I didn't know the optimum value . 1k variable resistors in-line and winding them down until it's sufficiently bright, but the contrast is OK.

You could maybe just start with some basic 220R resistors (or thereabouts) soldered in-line on the RGB signals.
If it's 75 ohms inside the monitor, then it'll drop the signal to about 1/4, I think. 

Apologies if I've got this all wrong - no monitor expert, but in-line resistors has fixed the same issue for me in the past.


Edited by John Bennett - 11 Jan 2019 at 10:26pm
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sbdesign Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 2019 at 11:31pm
cheers!
But will these EBAY LINK

If so, which value?
and what do I use on the ground pin?
And what lines? just the rgb?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Bennett Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan 2019 at 8:00am
You use the middle pin and a side pin and leave the other unconnected. It acts as a variable resistor rather than a potentiometer this way.
Put it in the RGB, the same way you get resistors in jamma to scart cables.
http://www.philwip.com -sibling 'fix-off' (I’m losing by miles).
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