Atari 7800 French to retrotink 2x pro

[mikesk8]

Hi, I was offered a French (secam) version of 7800 with RGB scart output to buy. I am wondering if this scart has composite pins available so I can add scart/composite dongle and then connect composite to Retrotink input? Thanks!

[marauder666]

Don’t.

 

video quality is terrible.  It just badly converts the internal luma/chroma into rgb.

 

[mikesk8]

Thank you for a tip:) so I guess PAL version + composite simple mod is the easiest way to go

[+Muddyfunster]

19 minutes ago, mikesk8 said:

Thank you for a tip:) so I guess PAL version + composite simple mod is the easiest way to go

PAL + a UAV mod would be your best solution if you have access to an SVIDEO compatible display.

 

I run a PAL console with UAV on with SVIDEO into a flat panel and also occasionally on a Commodore 1701 (Chroma /Luma).

 

[mimo]

1 hour ago, mikesk8 said:

Thank you for a tip:) so I guess PAL version + composite simple mod is the easiest way to go

Or the @marauder666@juansolo mod

[marauder666]

Or UAV and connect the composite out.  French Peritel version is a PAL console.  We modded one for better video, in the process ended up removing the RGB board to see what the stock video was like with our mod, it had the best s-video we've seen from any PAL 7800.  Shame the owner wanted RGB output which was much worse even with a few mods we put in it.

 

Somewhere in this thread is the French console.

 

 

NTSC 7800 has much better picture than the PAL one with any s-video or composite mods.

 

 

Edited August 22, 2021 by marauder666

[+slx]

2 minutes ago, marauder666 said:

We modded one for better video, in the process ended up removing the RGB board to see what the stock video was like with our mod, it had the best s-video we've seen from any PAL 7800.  Shame the owner wanted RGB output which was much worse even with a few mods we put in it.

2 minutes ago, marauder666 said:.  We modded one for better video, in the process ended up removing the RGB board to see what the stock video was like with our mod, it had the best s-video we've seen from any PAL 7800.  Shame the owner wanted RGB output which was much worse even with a few mods we put in it.

Is there any difference in the main board that would explain the better S-Video?

[marauder666]

The board layouts are totally different.  

Neither are perfect.

 

PAL suffers badly from colour rolling issues with certain colours which is temperature related in the Maria, TIA output doesnt have the problem.

 

NTSC has very slight interference issues, again varies with temperature.

 

Check the thread I posted above, its long, but lots of experimentation was done on a few machines over 6 months.

 

[juansolo]

Essentially it boils down to a few things. The NTSC and PAL 7800s are very different machines in how they go about things. Some things they do are fundamentally different and because of this, they have different problems.

 

The PAL machine first has 3 problems which dramatically effect it's PQ. First is that the MARIA and TIA have a shared colourburst clock which causes a large amount of diagonal rolling interference. The second is that the chroma (colour) signals from the TIA and MARIA are blended and have an effect on each other even though only one is used at a time. You can set one up well, but always at the expense of the other. The final problem we were unable to find a solution for, that's a colour rolling problem that appears to be inherent on the PAL MARIA and is heat related. That one varies from machine to machine and you just might be lucky to get a better one, but they all do it to a degree.

 

A common composite mod addresses none of these issues and will get a marginally better than RF picture. A UAV on it's own was not really designed with the PAL machine in mind. You will get an improvement, certainly by virtue of it being S-Video also (which is what the 7800 generates in essence), but again, the underlying issues are not addressed, and the UAV isn't quite as well balanced for a PAL machine either resulting it a slightly overdriven luma signal.

 

What the French RGB machine does is take the PAL luma and chroma signals as they would have been sent to a RF modulator and sends them instead to a very simple RGB encoder. Sadly this butchers the signal and can result in sub composite quality. I'd put it somewhere around a cheap composite mod, i.e. better than RF, but not by a huge amount. If you want to encode RGB from a PAL 7800's S-Video signal it's better to do so with something external like a Canon RGB-100.

 

The PAL machine then is a little bit of a lost cause. In the investigating PAL video issues thread above that @marauder666 posted, we went on a bit of a deep dive on the PAL probalems and came up with some solutions. They take two forms. One is an all-in-one DIY mod which is really for someone experienced with veroboard and with some skill of soldering. That can either get you S-Video or composite and it's vastly better than any current stand-alone solution. The other this we came up with is an add-on board for the UAV that deals with the chroma blending and clock issues that the AIO has built into it. If you've already got a UAV it's an easier mod, but neither are really for tack and go solderers.

 

The NTSC machine (covered in the second thread posted above) is a vastly superior machine in PQ terms. Out of the box it's dramatically better, just dropping a UAV into it gets massively better results than all the buggering about with the PAL machine. That too had a problem that certainly irritated me, in that it had fairly bad colour fringing on certain colours. Cleggy figured out that this was a timing mismatch between the luma and chroma and came up with a fix for that. That one @-^CrossBow^- now has a board for and is a really easy drop in to fix or it's also in the doc that we did if you're ok with veroboard. Again that's not all, the NTSC machine is much more susceptable to temperature variations, we're currently having a play in that area. But to be fair, at this point the picture is just damn good and we're being picky.

 

I've attached the current version of the doc we knocked together for anyone who wants to DIY it and CBA to read through those two threads.

AntiJackModDocV3-2.pdf

Edited August 22, 2021 by juansolo

[mikesk8]

Thanks for all your replies! I think I will be looking to locally get a decent PAL 7800 + basic composite mode. My main machines are Atari 8-bit computers, so 7800 would be just for fun with few games  I want to keep it as simple as possible