Atari ST 520 video cable to Scart

Good evening to all Atari fans.

First of all, I want to apologize for the English language, I don't know German well enough to write here

Recently I got Atari 520 ST system, but it quickly understood that no games work on a regular monochrome monitor

Therefore, I decided to make a cord to connect to the TV via Scart connector.

A few days ago I received a 13 din plug and started assembling the cable.

But I didn't succeed. I've looked through 5 schematics from different sites, English and French, but my German Atari doesn't show anything! ((((

I tried these everything on 2 TFT TVs and on one CRT, but i hadn't success. I tried many different pinouts combinations, different resistors, diodes, capacitors. But it didn't help.

Later I realized that there is no voltage of 12 volts on my Atari, on the video connector! What is needed to Scart. I had the 8th video pin connected to GND in my Atari. I disconnected it from GND and applied 12 volts from the power connector. And again I redid all the combinations of the cord, but i had anything on the screen (((

It's just some kind of horror.

Does anyone know the working cable schemantic for this Atari ST 520?

I have a motherboard revision B. (ST 520+) Like this:

File:ST Motherboard C070243 Rev C Factor6.jpg - AtariForumWiki

I understand that there is no composite signal?

Do not offer the option of buying a new cable on the Internet. I won't be able to do it now, and as far as I've heard, they often don't work either. And I'm not surprised (((

Please help, who can, who knows the scheme?
I've been trying to make a cable for 3 evening (((

Yes, of course, I switch the TV to the Scart input.

According to this scheme, I assembled the cord, the only nuance is that I did not take exactly the same diode, but the first one that I found in spare parts. It looks the same, glassy and small. I think it is not fundamental? when a diode passes current only in one direction?

Yes, i know this all, so I tested it all on three TVs.

I even connected my Soviet Spectrum computer to them, about which they directly write that it is not fully compatible with the scart connector and not all TVs can output images from it. But it works fine on these TVs. So I guess Atari would may too?

I think the problem is that all cords offer to take a composite signal from pin number 2. But in the information on the link from here: https://info-coach.fr/atari/hardware/interfaces.php (Atari Video Connector)

it directly says that a computer like mine does not have a composite signal on the second pin.

And yes, I saw it judging by the Atari schemantic, I have this second contact not connected anywhere at all!

It was the same with the 8th pin of the Atari video, judging by the diagram it was connected to the ground. I turned it off and applied 12 volts to it, so that the scart of the TV understood that it was necessary to switch

But anyway, I think i don't have the sync!

I just don't understand why all these schemes, for example from the first link:https://www.chzsoft.de/site/ha…ri-st-nach-scart-farbmodi

Why do all these circuits take only one VSYNC sync from the 12th pin. And where is HSYNC from the 9th pin of the atari? Maybe I need to do something about it?

Zitat

So which kind of signal is your russian computer using? RGB+H+V-Sync?

Yes, it using one Sync signal but it is not fully compatible with PAL standard, so maybe you will have a problems when your TV doesn't understand this signal correctly.

Zitat

does your ST has HF/RF-modulator

No, as I understand it doesn't have

As i think, i need to make one sync signal from Vsync and Hsync from Atari, but how? (((

The problem is that I have 0 volts on pin 2.
So I understand there is no any signal ((( When i have 5 and 4 volts on pins 12 and 9

I think I need to make one signal from of two synchronizations (H+V sync)

Zitat von 1ST1

it looks like you have to fix that little circuit on the mainboard.

But anyhow, even without the composite sync you should see the (unsynced) color signal on your TV scrolling up/down. If not, you may have connected pin 4 to ground?

I thought pin 4 should be open to get color video (as i want).
It should be connected to ground when the video is monohomic

From here:
https://info-coach.fr/atari/hardware/interfaces.php

Zitat

Monochrome detection (ST/STE):

This pin is connected to pin 17 of the MFP68901 circuit and is used to set the Atari in Hi-resolution when grounded and to Med/Low-resolution when left open. A transition on this pin generates a reset of the system. On a STE pin 3 must be left open for the detection to work.

External Video Clock (STE):

When pin 3 is grounded this input is used to provide an external video clock to the shifter. This allows synchronizing the video-timings with an external device so that a video Genlock device can be used without having to make any modifications to the Atari hardware.

As i understand i have problems like in this topic
https://www.atari-forum.com/viewtopic.php?t=30295

But i can't see any pics without registering on the foorum. Also i can't register. This forum accept only e-mail from g-mail or what. When i used one of my gmail addresses but didn't have any answer ((((

As I understand it, I don't have anything to solder on the board at all. Because there is simply no place for missing details.

I only need to form the synchronization signal from the another two.

In the topic above there is a description of how to do it. Connect the two signals together through resistors and diodes. Although it is not said which side the diodes should be ((((

I will try different options

The photo of my mainboard:

1ST1 Thank you for help!
I will try to make this scheme

I will also add a document here on how to do synchronization separately, not on the Atari board.

Maybe it will help someone someday
(although I haven't tried it)

1ST1 Thanks again for your help. Today everything worked!

Oddly enough, I found all the necessary spare parts on one board from an old TV tuner

I also had to disconnect 12 volts from the 8th pin. With it, the TV does not show image, but when there is 0 it works.

Also, sometimes the image moved slowly vertically. Therefore, I assembled the cord according to this scheme and when I added a 330 ohm resistor to the line from 2 to the 20th pin, then everything became fine and the image shift stopped.

I don't think that someone intervened there and took something out. Everything looks like from the factory.

Inside the computer is a metal screen, there is a hole for the module

But it was well sealed with copper foil.

I think it's factory maded.

Such things, like in this computer, do not happen often, but they still happen, I'm not the first

My computer was manufactured on August 1985. Is the serial number small? 1001433 (1433 ?) I have TOS version 1.0, thank's it's built inside. Because as I read, it could be separate on a diskette an early computers

Yes, I have plans to replace the TOS, but it is not fast, because here I have nothing. For this i need a programmer, memory chips and an ultraviolet lamp to erase them.

First I want to buy and adapt the gotek here, but that will be another story. I hope with fewer steps than in this case))))