MAME cab VGA to scart

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Hi all.

My mate has a MAME cab thats playing up. There is no picture. The first thing I looked at was the cable from the PC to the TV

IMG_2344.jpeg


Athough it looks a bodge it SEEMS ok to me. I don't really want to put this back and would rather buy another.

So the question is this. This lead there is a wire from the scart (that single blue one) that was wired to the 5v on the PSU.

When looking to buy a replacement, i'm not sure if it will work. Take this one for example

https://www.amazon.co.uk/Wentronic-50071-GB-SCART-Density-Audio/dp/B000L0Z93M/ref=sr_1_3?adgrpid=55759410920&dchild=1&gclid=CjwKCAjwyIKJBhBPEiwAu7zll_m4TJm828rAXJMAbKJMftgDsSqVEBVqmsOCBEwAhgFPPIKfMLchUhoCd7oQAvD_BwE&hvadid=259040787487&hvdev=c&hvlocphy=9046397&hvnetw=g&hvqmt=e&hvrand=1002970894101118841&hvtargid=kwd-488801373992&hydadcr=3513_1759287&keywords=vga+to+scart&qid=1629611018&sr=8-3

Will this work? Don't i need voltages going to the scart socket?

Any help or suggestions what would work out of the box would be great.

Cheers

John
 
Sbdesign

Sbdesign

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Have you opened the start end? or is this just a pic he sent you?
Maybe some work done in the connector.

The reason I say keep, is - if it worked previously, I would imagine the issue isn't this. And this previously working cable maybe the better guarantee.

Also- by the time you splice up a new cable, you may end up with something similar anyhow.

Just a suggestion... some other members who have done this type of thing will give some better info than I can.
 
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He sent me the lead, and it LOOKS to be ok. The soldering is poor but all looks connected etc. Also from what I can see has components missing, resistors etc. I just wanted a guranteed worker if possible. It's something I didn't really want to put back in. Please tell me if i'm over thinking it :)
 
Sbdesign

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If I was tackling it - yes
But there is people on here with 10 times my knowledge on this type of thing.

So Just wait to others chime in, and no doubt debunk everything I am saying. :)
 
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Fantazia2

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Video signal connections shouldnt need resistors as VGA spec is 0.7v 75ohm on the RGB singnals which is the same as RGB input on Scart on TVs.

The only connection that could possibly need a resistor is the blanking pin on the Scart (pin 16) that some TVS need to tell it that the input is RGB, it needs to be fed a voltage between 1v and 3v, pin 8 is the status, feeding that 5v will force the TV to switch to the scart input automatically, but the spec says 5v to 8v is on/16:9 and you need 9.5v to 12v for on/4:3 depending on the TV some dont care about the 16:9 signal.

Scart info here: http://en.wikipedia.org/wiki/SCART
 
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ZedEx48K said:
This is the wiring you need to use.

vga2euro.gif
Click to expand...

I came across this, but wasn't sure about resistors etc. The wire that went to the PSU is pin 8 so probably wired to the 12v and not the 5v like i originally said.

Thanks
 
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ZedEx48K

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I know one of the lines is for function switch (auto switch to scart input), the other fast switching, but I think that can denote 4:3 or 16: 9, years since I made one of these.
 
Shun

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Don't know if you got this working or not but, I assume that the PC was originally setup to output 15khz rather than 31khz as that is a passive cable and it isn't going to convert 31khz to 15khz on its own.

Perhaps the PC updated itself or something and changed the video settings. What happens if you plug in an old VGA monitor into the PC with a standard VGA cable. Does it show video then? If it does, then its outputting VGA video @31khz and is probably why the TV isn't showing a picture.

Usually if you feed 31khz to a SCART tv, you usually get a rolling picture, but it could be that the resolution changed as well.

Do you know what video card the PC is using?

Thinking about it, another issue could be that if the PC motherboard has onboard graphics, perhaps its outputting from there rather than a separate video card?
 
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Shun said:
Don't know if you got this working or not but, I assume that the PC was originally setup to output 15khz rather than 31khz as that is a passive cable and it isn't going to convert 31khz to 15khz on its own.

Perhaps the PC updated itself or something and changed the video settings. What happens if you plug in an old VGA monitor into the PC with a standard VGA cable. Does it show video then? If it does, then its outputting VGA video @31khz and is probably why the TV isn't showing a picture.

Usually if you feed 31khz to a SCART tv, you usually get a rolling picture, but it could be that the resolution changed as well.

Do you know what video card the PC is using?

Thinking about it, another issue could be that if the PC motherboard has onboard graphics, perhaps its outputting from there rather than a separate video card?
Click to expand...

Hi

This was for my mate. I updated the harness with the resistor correct to the drawing. He had some help and it was decided that the PC was old as sh*t and was intermitantly faulty (apart from the TV output problem). He has decided to start again with a Pi. Probably not a bad idea if you don't mind that kind of thing.

Thanks for all your help guys.
 
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Ropi Jo

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Although many will poo-poo this, I just used S-VID from an old card directly to the appropriate pins of the SCART, and to me the pic is great.

I just don't see the need to complicate things any more than this.

Standing back and waiting for incoming.....

Ropi Jo2021-09-30 12:41:15
 
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