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PAL Atari 2600 Jr. Composite Mod


Albert

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http://www.itstoast.co.uk/atari/For our European visitors who would like a better way to hook their PAL Atari 2600 Jr. to their television, Oliver Radford (aka Radfoo) has created a composite modification that you can perform if you're handy with a soldering iron. You can find Oliver's modification on his Atari 2600 Page, which includes detailed instructions and photos to guide you along.
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quote:

Originally posted by atarinvader:

Is there a mod for a PAL 6 switcher?

 

Not yet, but I do have one I could take a look at (maybe in a couple of weeks).

 

The mod should not be much different on a 6 switcher, it would just be a case of finding the Chroma and Audio connections.

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quote:

Originally posted by liveinabin:

Oh yeah, radfoo, I'm gonna get some bits tomorrow to start mine, i'm off to Maplins - which resistors and pots should I get?

I'd love to see a picture of your finished board.

This is so cool.

 

Maplin product code uh00a should do the trick as its quite small and can easily fit inside an existing Atari Junior case.

 

The resistor is not that crucial as it only changes black/grey colours (try Pole Position and adjust line 7 with a spare 1k pot), if you already have somthing around 1k or 2k they would both work fine.

 

I'll perhaps add better list of whats needed on my web site.

 

[ 03-24-2002: Message edited by: Radfoo ]

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Radoof: I've been trying to get a composite signal on my 6 switcher from after the video buffer. I though it would be cleaner than combining the signals off the Stella chip.

 

After the buffer the 3 luma signals, sync and chroma combine before going to the modulator, but I can't get anything at this point (pin 12 connecting the top and main board). Any idea why?

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quote:

Originally posted by atarinvader:

Radoof: I've been trying to get a composite signal on my 6 switcher from after the video buffer. I though it would be cleaner than combining the signals off the Stella chip.

 

After the buffer the 3 luma signals, sync and chroma combine before going to the modulator, but I can't get anything at this point (pin 12 connecting the top and main board). Any idea why?

 

I know, I gave up trying it that way as some weird stuff seems to go on in the "buffer".

 

Have you looked at the extra PAL circuit (left of stella on a junior), you might find you need to add somthing from there, you could also try pin 20 maybe?

 

[ 03-28-2002: Message edited by: Radfoo ]

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Ah right, so maybe its a good idea to ditch the resistor and use 3x1k pots instead of 2 yeah?

Where did you stick all this on the circuit?

Oh yea, and did you get rid of the big silver rf box?

(sorry to ask so many questions - i don't know one end of a pot from the other - just one more)

The croma and audio conns, did you solder them from the pins at the outer edge of the circuit, or the other end of the resistors?

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quote:

Originally posted by Radfoo:

Have you looked at the extra PAL circuit (left of stella on a junior), you might find you need to add somthing from there (pin 20 maybe!?).

 

I'm using a 6 switcher, so its all different.

 

Isn't pin 20 just +5V? So what exactly does it do when added to the luma, sync and chroma?

 

I'm gonna try and get a 'scope and see if I can get a buffered signal tommorow.

 

[ 03-24-2002: Message edited by: atarinvader ]

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yeah, I've cracked open a couple of sixers, they might as well be a different console. tell you what, just solder everything together, it won't work, but then you can give me the TIA chip from your (now) broken atari I have a woodgrain with a dud one.

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quote:

Originally posted by liveinabin:

Ah right, so maybe its a good idea to ditch the resistor and use 3x1k pots instead of 2 yeah?

Where did you stick all this on the circuit?

Oh yea, and did you get rid of the big silver rf box?

(sorry to ask so many questions - i don't know one end of a pot from the other - just one more)

The croma and audio conns, did you solder them from the pins at the outer edge of the circuit, or the other end of the resistors?

 

That is a lot of questions, but no problem:

 

3x1k pots would work fine.

 

The bits are small so you can put them half way down the wires, just wrap them in insulating tape when your done.

 

No, you can leave the RF box but it won't work any more.

 

The yellow arrows point exactly to the solder point of Chroma and Audio.

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quote:

Originally posted by liveinabin:

tell you what, just solder everything together, it won't work, but then you can give me the TIA chip from your (now) broken atari I have a woodgrain with a dud one.

 

You've tried the mod on a PAL sixer before?

 

It uses all the same chips as a Jr model, but its just layed more neatly, so it should, in therory, work.

 

I've looked up the buffer in RS and it seems that its just a basic non-inverting buffer, and that the signal is too weak after, which is why you can't get a signal, I'm gonna look into it a bit more.

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Right, bits bought, Atari open.

I found a good bit on Maplins, they do a double phono-socket in a chassis mount which (after you've opened the 2600 back a little for the sockets to poke through) sits very happily between 2nd joyport and the top-right screw mount, doesn't need fixing in at all (all the existing stuff holds it in place) and it looks great - part no. JK15.

 

aanyway HELP!!!!! just one more bit of advice, got the potentiometers - which look like so:-

 

pin at top, dial in middle, 2 pins at bottom (the ones you recommended radfoo), what solders to what? I'm figuring the top pin is either just to hold it on the board but further to that, I don't know - please help

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quote:

Originally posted by liveinabin:

aanyway HELP!!!!! just one more bit of advice, got the potentiometers - which look like so:-

 

pin at top, dial in middle, 2 pins at bottom (the ones you recommended radfoo), what solders to what? I'm figuring the top pin is either just to hold it on the board but further to that, I don't know - please help

 

Take a look at this picture from the web site http://www.itstoast.co.uk/atari/gfx/pot.gif. I think that should answer your questions.

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Right, I did it! It worked a treat - thanks very much. Only slight problem I get is one of contrast, either I have the black coming through a mid grey and everything on the screen is stable, or as a near black and everything seems to horizontally distort a bit. Its not a major problem (though I might alter one of those pots to make it accessible as a 'contrast' control from the console rear)

Thanks very much for your help, my All-black 2600 looks (and sounds)the business

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quote:

Originally posted by liveinabin:

By the way,I found that Pitfall and Centipede are great 'control' carts for setting the pots.

 

My contrast problem is playing hell with Pole Positions title screen

 

Cool, I am pleased you have had some success.

 

Not sure about the contrast problem though, do you mean it just looks too light? What does they grey part of the track look like in Pole Position or is it just the title screen thats the problem?

 

Does Pitfall and centipede look good?

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quote:

Originally posted by liveinabin:

Right, I did it! It worked a treat - thanks very much. Only slight problem I get is one of contrast, either I have the black coming through a mid grey and everything on the screen is stable, or as a near black and everything seems to horizontally distort a bit. Its not a major problem (though I might alter one of those pots to make it accessible as a 'contrast' control from the console rear)

Thanks very much for your help, my All-black 2600 looks (and sounds)the business

 

Right, I have re-read your above message and I think uderstand the problem. What I suggest you try is as larger resistor on line 7. The higher the resistance the darker grey/black colours will become.

 

0ohm = light grey

2k/3k = black

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Ah right, but I used a variable resistor (1k pot). So a 2 or 3k Pot will be better? I mean, would it give me the contrast while stopping all the white pixels freaking out?

its just that, with the pot I'm using, I can get a nice black, but at the expense of everything else.

 

[ 03-26-2002: Message edited by: liveinabin ]

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quote:

Originally posted by liveinabin:

Ah right, but I used a variable resistor (1k pot). So a 2 or 3k Pot will be better? I mean, would it give me the contrast while stopping all the white pixels freaking out?

 

I suggest you go back to your stable but high contrast settings and then add higher resistance to pin 7. A 3k pot might be a good idea. This should sort out the contrast.

 

Hope this helps.

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No, the choices I have with the pots I've got are:- stable but low contrast (ie. grey background, washed out colour but nice even pixels) or unstable with high contrast (large distortion on anything that contrasts with the background, ie. a vertical line like the trees in Pitfall will appear zig-zagged)

sorry, I should have explained it a bit better

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quote:

Originally posted by liveinabin:

No, the choices I have with the pots I've got are:- stable but low contrast (ie. grey background, washed out colour but nice even pixels) or unstable with high contrast (large distortion on anything that contrasts with the background, ie. a vertical line like the trees in Pitfall will appear zig-zagged)

sorry, I should have explained it a bit better

 

Try the following in order,

 

1. I suggest you go over the instructions again and just double check that everything is connected correctly and there are no short circuits.

 

2.If everything is correct, I suggest you get a stable picture again. Then try adjusting the Atari's onboard colour control (nr the on/off button). Only make slight adjustments and only change whilst the Atari is turned off.

 

3.Then try a bigger pot on line 7 as discussed before.

 

4.If there is still a problem i'll need to investigate further, maybe you could try another TV, though I tried 4 and they all looked good.

 

Hope this helps.

 

[ 03-26-2002: Message edited by: Radfoo ]

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