Let's talk about Scart

[Duffygag]

Hello Everyone, while making a VGA to Scart cable for my EU crt I quickly noticed how the information on the wiki is far from complete/accurate and finding the correct adjustment for making the correct cable was quite a daunting task, information is scattered all over the web and there's not a real unique scenario working for all systems.

In shorts I think we would all benefit to keep the information in a single thread, I want to hear your findings and different user cases for your setups, are you using 75ohm resistors for your rgbs, potentiometers like a lot of trinitron users, 470ohm resistance for the rgb switch line (you should), are your color too saturated, is the image too bright, do you use capacitors in your cable, are you putting a resistor between pin 20 and 16 on the shart and so on.

Let me know what you think, from personal experience this would help immensely if making a cable from scratch.

[retrorepair]

I'm a Trinitron user and I use 75ohm resistors to GND as otherwise the colours are totally blown out. Other than that I use a 180ohm resistor from 5v to blanking as per any other scart cable I have.

This cable works perfectly with any other CRT or LCD I've plugged it into as well.

I also had to do a lot of searching to find this information. I was surprised a lot of people recommend using a MiST SCART cable which does NOT have the same pinout on the VGA connector.

[pacoarcade]

I use this cable with a Rankie HDMI to VGA adapter and this configuration:

Code: Select all

direct_video=1; 
composite_sync=1;

The 470Ω resistor for CSYNC attenuates the signal to ~400mV

mister-vga-a-scart.png (19.19 KiB) Viewed 9196 times

[akeley]

I also had to do a lot of searching to find this information. I was surprised a lot of people recommend using a MiST SCART cable which does NOT have the same pinout on the VGA connector.

So how come it works perfectly with every core I've tested, apart from the ST?

I agree that finding info about it is a daunting task, which is why I eventually gave up on modding my MiST cable and just left it as is. So far it did not break anything. Colours are off on some of my Trinitrons but ok on others. If there was clear, non conflicting info, with dummy-level instructions on how to apply these resistors I would probably have another go at it.

[Duffygag]

I think the wiki page was written by a non native English and can be confusing, also it gives you the port pinout if I recall correctly, while on the diagram it looks like is giving the cable schematics, best way would be to put the solder side connector pinouts like it should be when you are making a cable.

Really we should use a common ground (ahah) when making this cables for consumer CRT.

[akeley]

Things I'm interested in, as a Direct Video user:

-are there any known differences between outputting via I/O and Direct Video?
-is MiST cable really different from the MiSTer one, and if it is, how can it affect things?
-is the 470 Ohm resistor described in Direct Video wiki really needed, if I connect straight to the SCART in my TV?
-about the colour-affecting resistors, as mentioned in this thread I've made some time ago. (and in links from it). There are mentions of 75/1000 Ohm resistors, and also a 2k potentiometer. Which one is best? Is it separate thing from that aforementioned 470 Ohm resistor?
-could any of the above be the reason the Atari ST core is not syncing properly on my setup?

Another issue is that the last time I soldered something was ~40 years ago. I'm absolutely out of my depth but couldn't find anybody in my area who would attempt doing these modification for me. I guess I could handle some very simple tweaks, but would need to be told precisely what to do. For example, where do you put all these resistors?

[retrorepair]

I also had to do a lot of searching to find this information. I was surprised a lot of people recommend using a MiST SCART cable which does NOT have the same pinout on the VGA connector.

So how come it works perfectly with every core I've tested, apart from the ST?

I don't really know because MiST uses pin 14 to output 5v for AV switching where MiSTer uses pin 9.

[paulbnl]

Pin 14 is Vsync on both MiST and MiSTer which is forced high with composite sync. It's not 5v.

[retrorepair]

Pin 14 is Vsync on both MiST and MiSTer which is forced high with composite sync. It's not 5v.

I hadn't realised that. Makes sense why that works then.

I was mislead by pin 9 on MiSTer being 5v (when jumpered as such) which I've always used.

[Duffygag]

What do you think this is ? See red and white especially:

8kXZOw6.jpeg (3.36 MiB) Viewed 5858 times

Edit: Solved this, wrong resistore on r15 my bad!

[BlockABoots]

I thought for RGB pin 6 on the VGA connector goes to ground and not pin 10???

[cpasjuste]

I use this cable with a Rankie HDMI to VGA adapter and this configuration:

Code: Select all

direct_video=1; 
composite_sync=1;

The 470Ω resistor for CSYNC attenuates the signal to _400mV

mister-vga-a-scart.png

Hi guys,

Sorry to bump an old thread but I just want to confirm this wiring works fine here on an old Sony trinitron CRT, either via vga (analog io) or HDMI (direct video). Thanks !