Modding French 7800 to composite?

[tajume80]

Hi!

 

I recently bought French 7800. Unfortunately the picture quality via scart is really bad. While playing 2600 games there is ugly thick "scanlines" and 7800 don't look good either. It seems my that the rgb board is either broken or just bad. I attached a photo where you can see the horizontal lines.

 

So I'm planning to mod the console, so I can use composite.

 

The problem is that the motherboard is slightly different than pal version.

 

Is there a way to mod the French version to composite?

[+Mitch]

From the pic I would say you have a shielding issue, maybe a bad cable. Does the cable look original?

 

Mitch

[Rastignac]

Is there a way to mod the French version to composite?

Scart gives RGB + Composite + audio.

Some pins are the RGB ones, others are the composite ones.

TV set looks first for the RGB signal, then drops to composite signal if RGB is not found. So, removing/pushing RGB pins from the Scart forces composite output.

(There are also cheap "dongles" with Scart-in --> RCA-out).

[tajume80]

From the pic I would say you have a shielding issue, maybe a bad cable. Does the cable look original?

 

Mitch

The cable is original and I've started to mod the console to composite and it shows the same problems as via scart. The problem with the mod at the moment is that the motherboard is different than the pal version, so I only managed to get black and white picture out of the motherboard. I suspect that I need to take out and add some resistors to the motherboard because of the differences between pal and secam versions.

[tajume80]

Scart gives RGB + Composite + audio.

Some pins are the RGB ones, others are the composite ones.

TV set looks first for the RGB signal, then drops to composite signal if RGB is not found. So, removing/pushing RGB pins from the Scart forces composite output.

(There are also cheap "dongles" with Scart-in --> RCA-out).

Thanks for the advice, but in this case the picture quality from the rgb board (or the console itself) gives a really bad picture quality via rgb and via composite (I've started to mod the console to composite, but it only shows black and white colors). I mentioned in a new post that I suspect that I need to remove and insert some resistors, so I might get colors, and to get rid of the vertical lines. I'm also suspecting that the secam 7800 might also be broken.

[+Mitch]

Can you post a pic of the system board?

By the way, there isn't a secam 7800, only PAL and NTSC.

 

Mitch

[tajume80]

Can you post a pic of the system board?

By the way, there isn't a secam 7800, only PAL and NTSC.

 

Mitch

Ok, good to know! I didn't know about that fact it isn't secam.

 

The pictures aren't that great, but I'll take a better shot later. I've removed the rgb daughterboard and some of the resistors that have to be removed for the composite mod. The thing is that I need to know which resistors I have attach to the motherboard, as some of them are missing in the French version.

Edited February 12, 2019 by tajume80

[+Mitch]

That looks like the standard PAL 7800 board with the alt memory daughter board.

 

Mitch

[tajume80]

Does anyone know what resistors I need to these areas which I have marked?

 

The French 7800 does not have them. I've removed some resistors needed to the composite mod. When compared to the regular pal version, it seems to have resistors in places which the French does not have. I guess I need them to complete the composite mod, because otherwise the picture is black and white. It might also affect the picture quality.

 

The other picture is from one of the mod tutorials I've found via Internet.

[+Mitch]

I think this is the best that I have right now.

 

[+slx]

My French 7800 does not show colors in 2600 mode, any ideas on why/how to fix appreciated as well. Unfortunately these seem to be such rare beasts that next to nothing is on the web for them.

[+Mitch]

Check the chroma connection on the 2600 side.

 

Mitch

[tajume80]

Does anyone know anything about the resistor/transistor I've marked on the picture. You can find it on the regular pal motherboard, but not on the French version. I'm still wondering how to make the composite mod, I just have to know what parts I have to buy.

 

I'm starting to think that maybe I should just buy a 2600 Junior to play my Pal 2600 games, and play ntsc 7800 and 2600 on my ntsc 7800 because the French 7800 is either broken or just bad. Too bad for me, because the French 7800 wasn't cheap. Too bad about the really bad picture quality. I thought that having a scart version would have been the best version out there

Edited February 16, 2019 by tajume80

[mimo]

Have you tried a different TV?
My French 7800 looks terrible on my LCD that displays s-video 8 bit consoles really nicely.

Looks fine on my Sony CRT though.

On my big plasma screen it displays terribly with the genuine peritel cable, but perfectly fine on the cable I made myself for my ST.

[tajume80]

Have you tried a different TV?

My French 7800 looks terrible on my LCD that displays s-video 8 bit consoles really nicely.

Looks fine on my Sony CRT though.

On my big plasma screen it displays terribly with the genuine peritel cable, but perfectly fine on the cable I made myself for my ST.

Yes, I've tried three different types of tv's: oled with framemeister, lcd and crt tv. Most surprising was the crt, as it looked as horrible as on modern tv sets.

 

I suspect that there is something wrong with the chips.

 

Maybe I should try it with the ST cable.

Edited February 21, 2019 by tajume80

[tajume80]

Has anyone tried to mod the French 7800 to s-video? Is it possible?

[CatPix]

It should be possible. If I'm right, the 7800 doesn't output RVB, but like the Atari 2600, luma and chroma. The fastest way is to pick up the video signal right form the video chip (that would be MARIA) and built your own video amp from it.

 

https://www.atarimax.com/jindroush.atari.org/7800cmar.html

 

But I don't remember if MARIA include the TIA video chip or not, which mean you'd have to do that mod for both chips.

[twoquickcapri]

Pin 2 of the 13 pin connector should be composite video and pin 1 is audio. Any Atari ST composite video cable should work with the French 7800.

[CatPix]

I fired my 7800 today and mine has the same issue with thick scanlines and bleeding red and green at the scanline edges. I'm gonna check with other 7800 I know of but that might be a common problem with them, or just how they were made back in the day.

I mean, the SECAM Atari 2600 is even worse

I'll try on a CRT too, I played mine quickly on my 80 cm LCD which probably didn't helped the issue.

[Jinks]

You measure your tvs in cm there? We are metric in Canada but do inches for TVs.

[CatPix]

Always. You see TV sold in inches, but this has no legal value whatsoever and you could sell a 36CM TV as a 32"

But people use that, which always confuses me.

 

https://www.conforama.fr/tv-son-multimedia/tv-television/televisions/c/080101/NW-1373-taille-ecran~de-80-a-100~cm/

(you can see in the links ans choices that it is in CM

 

Can't find a better pic than that :

They were advertized that way before, but not I guess it's cheaper to just drop the provided picture from the brand without the size added.

 

Edit.

I tested my 7800 on a CRT today and...

 

All defaults are gone !

 

Well it's never easy to snap a CRT but here are some pictures anyway :

 

 

 

 

 

 

So my guess is that the RGB board is tuned to display on the regular CRT TV of the era, but that some imperfections are revealed with LCD displays or maybe, depending on what you use, with upscalers that obviously will also take the defaults and worsen them.

Edited March 3, 2019 by CatPix

[Lynxpro]

You measure your tvs in cm there? We are metric in Canada but do inches for TVs.

 

 

Remember, everything in the European Union has to be sold in Metric units. They were giving British pubs a bad time over selling drinks in Pints. Granted, 1L is more than a Pint but the disagreement wasn't related to purchasing value.

 

And don't give me a bad time about digressing because alcoholic consumption and retro gaming go hand-in-hand.

 

 

 

With all of that having been said, I wish we [North America] would've adopted SCART... I would've assumed Thompson-era RCA TVs would've come equipped with them here, but I'm probably wrong in assuming that...

Edited March 4, 2019 by Lynxpro

[CatPix]

The RCA Dimensia and RCA Colortrak 2000 came with SCART (renamed EIA multiport).

 

Unfortunately, it appears that RGB isn't enabled on the Dimensia, and probably not on the Colortrack 2000.

[+slx]

SCART is great from a versatility point of view and the rather big and mostly accessible plugs make it easy to fix/change/etc. connections inside.

 

When every device in Europe had SCART (from about 1985 to 2000 I‘d say), it was really convenient.

 

On the downside the mechanical quality of the connector body is often poor and they are a pain to insert without looking, as into an LCD hanging on the wall.

 

A fully connected SCART cable is a beast to wrestle and over time there used to be many ‚reduced‘ types e.g. for connecting a VCR to a TV which won‘t work for RGB, so you always have to think before using a specific cable.

 

I bought a homemade SCART cable for a Jaguar recently and the guy who built it chose not to connect the line that switches the TV to the Jag‘s Input automatically when the Jag is turned on, one of the features you wouldn’t get with Cinch connectors. SCART it is, so nothing to complain but one feature missing...

 

 

 

 

 

 

 

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[gambler172]

Seems that i have luck...my french system works great