Let's talk about Scart

Discussion about displays and related hardware including MiSTer filters and video settings.
Duffygag
Posts: 95
Joined: Tue Nov 03, 2020 10:57 am
Has thanked: 12 times
Been thanked: 25 times

Let's talk about Scart

Unread post by 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
Posts: 257
Joined: Sun May 24, 2020 9:06 pm
Has thanked: 64 times
Been thanked: 13 times

Re: Let's talk about Scart

Unread post by 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
Posts: 72
Joined: Mon May 25, 2020 8:41 am
Has thanked: 75 times
Been thanked: 13 times
Contact:

Re: Let's talk about Scart

Unread post by 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
mister-vga-a-scart.png (19.19 KiB) Viewed 6147 times
Attachments
rankie-csync-470.jpg
rankie-csync-470.jpg (96.78 KiB) Viewed 5962 times
akeley
Top Contributor
Posts: 1303
Joined: Mon May 25, 2020 7:54 pm
Has thanked: 416 times
Been thanked: 399 times

Re: Let's talk about Scart

Unread post by akeley »

retrorepair wrote: Wed Nov 04, 2020 4:22 pm 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
Posts: 95
Joined: Tue Nov 03, 2020 10:57 am
Has thanked: 12 times
Been thanked: 25 times

Re: Let's talk about Scart

Unread post by 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
Top Contributor
Posts: 1303
Joined: Mon May 25, 2020 7:54 pm
Has thanked: 416 times
Been thanked: 399 times

Re: Let's talk about Scart

Unread post by 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
Posts: 257
Joined: Sun May 24, 2020 9:06 pm
Has thanked: 64 times
Been thanked: 13 times

Re: Let's talk about Scart

Unread post by retrorepair »

akeley wrote: Thu Nov 05, 2020 9:59 am
retrorepair wrote: Wed Nov 04, 2020 4:22 pm 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
Core Developer
Posts: 205
Joined: Sun May 24, 2020 8:48 pm
Has thanked: 18 times
Been thanked: 196 times

Re: Let's talk about Scart

Unread post by paulbnl »

Pin 14 is Vsync on both MiST and MiSTer which is forced high with composite sync. It's not 5v.
retrorepair
Posts: 257
Joined: Sun May 24, 2020 9:06 pm
Has thanked: 64 times
Been thanked: 13 times

Re: Let's talk about Scart

Unread post by retrorepair »

paulbnl wrote: Thu Nov 05, 2020 7:16 pm 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
Posts: 95
Joined: Tue Nov 03, 2020 10:57 am
Has thanked: 12 times
Been thanked: 25 times

Re: Let's talk about Scart

Unread post by Duffygag »

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

8kXZOw6.jpeg
8kXZOw6.jpeg (3.36 MiB) Viewed 2809 times

Edit: Solved this, wrong resistore on r15 my bad! :)
User avatar
BlockABoots
Posts: 43
Joined: Wed May 27, 2020 8:21 pm
Has thanked: 7 times

Re: Let's talk about Scart

Unread post by BlockABoots »

I thought for RGB pin 6 on the VGA connector goes to ground and not pin 10???
cpasjuste
Posts: 1
Joined: Wed Mar 06, 2024 10:15 pm

Re: Let's talk about Scart

Unread post by cpasjuste »

pacoarcade wrote: Wed Nov 04, 2020 4:39 pm

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 ! :)

Post Reply