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7800 image problem.


MPANS

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Sorry if this is the wrong place to post.

I acquired a 7800 French, it has a 13 pin rgb output.

I don't have 7800 games, I have 2600, whatever cartridge I put in, there are no colors, the image is brown.

What could be happening?

IMG_20240106_121926.jpg

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7800 French is a 7800 PAL with a cheap RGB scart output card.

It has most of time the "Asteroids" game ROM embedded on the mother card.

 

So if you don't put cartridge inside the 7800,  the embedded Asteroid game will start when you power on the 7800.

 

Is it the case for you ? when you power the 7800 without cartridge, do you have Asteroid starting ? and is it in color ?

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The French 7800 is a PAL 7800 that fires it's output through an RGB transcoder. It's not a very good one sadly... As suggested above, boot it without a cart and you should get 7800 Asteroids in colour. If you do not, that's not a good sign... If you do, it is as it means it's probably one of two things. If you're bunging a SECAM 2600 cart into it, that might be a reason. However if you're putting a PAL 2600 cart into it, then it might just need the chroma trimmer tweaking. That requires the top taking off and ideally the shield also as it's likely the trimmer is hot-snotted or glued into position (you'll need to remove that). There are two one above the other underneath the cart slot. the one nearest the cart slot adjusts the MARIA (7800) chroma, the one underneath that does the TIA (2600) chroma. It may just need a little adjustment there. You do this whilst running a 2600 cart, being careful not to touch anything you shouldn't.

Edited by juansolo
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10 hours ago, Avenger75 said:

7800 French is a 7800 PAL with a cheap RGB scart output card.

It has most of time the "Asteroids" game ROM embedded on the mother card.

 

So if you don't put cartridge inside the 7800,  the embedded Asteroid game will start when you power on the 7800.

 

Is it the case for you ? when you power the 7800 without cartridge, do you have Asteroid starting ? and is it in color ?

Yes, it has the steroid built in.
And the asteroid begins altered and with color problems.
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7 hours ago, juansolo said:

The French 7800 is a PAL 7800 that fires it's output through an RGB transcoder. It's not a very good one sadly... As suggested above, boot it without a cart and you should get 7800 Asteroids in colour. If you do not, that's not a good sign... If you do, it is as it means it's probably one of two things. If you're bunging a SECAM 2600 cart into it, that might be a reason. However if you're putting a PAL 2600 cart into it, then it might just need the chroma trimmer tweaking. That requires the top taking off and ideally the shield also as it's likely the trimmer is hot-snotted or glued into position (you'll need to remove that). There are two one above the other underneath the cart slot. the one nearest the cart slot adjusts the MARIA (7800) chroma, the one underneath that does the TIA (2600) chroma. It may just need a little adjustment there. You do this whilst running a 2600 cart, being careful not to touch anything you shouldn't.

Unfortunately, the asteroid is also very dirty.

Probably the problem is in the RGB output.

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They are sadly difficult to deal with. We tried to get a good pic from an equally misbehaving French 7800 and we could get a far better image by removing the RGB transcoder completely and setting it up with an S-Video out (what it is essentially sending to the transcoder, but it does mess with the levels somewhat before hand). As it was we did the best we could in that case as the person we were doing it for wanted to keep the RGB side of things. The fun and games we had with it are documented here:

 

Edited by juansolo
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  • 4 months later...

Hello to everyone!!

The Atari 7800 has been repaired!!

Now there is another problem.

The TV I bought has an AV SCART port.

The image flickers constantly, I tried it on another TV that has an RGB SCART and it plays perfectly.

My question now is, what solutions are there to connect the Atari 7800 to my TV that does not have an RGB SCART?

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If it has non RGB SCART it's likely wired for Composite Video and possibly S-Video. I don't think the RGB 7800 outputs sync over composite, if it did it should work, i.e. you'd get a picture but it'd be composite video not RGB.

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