2600 Composite mod

Any 8bit repairs, images, cool things, upgrades etc.
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rubber_jonnie
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Re: 2600 Composite mod

Post by rubber_jonnie »

exxos wrote: Fri Apr 26, 2019 11:27 am
Modulator causes a lot of interference, so you really have no choice but to remove it. It's one reason my design tapped directly into the TIA itself ( then every component after it relating to the video gets removed and replaced) .
Cool, makes sense to me, thanks.
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800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
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Re: 2600 Composite mod

Post by exxos »

Dinnertime now :lol:

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IMG_4085.JPG
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Re: 2600 Composite mod

Post by exxos »

Well we have video, kind of :lol:

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Re: 2600 Composite mod

Post by exxos »

Okay so that resistor I wasn't sure was needed or not, is actually needed then :lol:

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Now to start dismantling the motherboard video circuit to rule out all this interference, hopefully..


EDIT:

Back to pole position as my "test game"..

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Re: 2600 Composite mod

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So this seems to be picking up a lot of interference somehow, somewhere... But I'm not really sure of this interference is a problem with my monitor or not, as I see interference issues when my ST is connected..

So really it needs other people trying this out to see what video quality they get ;)
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Re: 2600 Composite mod

Post by exxos »

OK so, added the caps on the bottom... :lol:

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Picture quality has now dramatically improved..

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I am basically at the point I was originally,Where the black seems too bright, but if I reduce the brightness level, obviously the colours go darker as well, and then I think it is too dark overall so there does not really seem to be a solution for this :roll:

I will start probing about to see if I can increase it any better...Though I think some of the vertical banding on the blue, is actually my monitor...
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Re: 2600 Composite mod

Post by rubber_jonnie »

exxos wrote: Fri Apr 26, 2019 1:52 pm So this seems to be picking up a lot of interference somehow, somewhere... But I'm not really sure of this interference is a problem with my monitor or not, as I see interference issues when my ST is connected..

So really it needs other people trying this out to see what video quality they get ;)
My own comp mod has some interference too, not dissimilar to what you see, even with the tin back on.

Will get it done on my other 2600, see what comes out. Have you tried yours with the shield back on?
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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Re: 2600 Composite mod

Post by exxos »

rubber_jonnie wrote: Fri Apr 26, 2019 2:25 pm Will get it done on my other 2600, see what comes out. Have you tried yours with the shield back on?
Not yet, it may well help, im just trying to improve the colour.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: 2600 Composite mod

Post by exxos »

My findings so far...

Grounding the oscillator seems to help tiny bit with colour and interference..

I also have a pot which is actually set to 660R In series with a 100pf (2x47pf) capacitors to ground.. This is odd as it seems be acting as a filter, as there seems to be a sweet spot when the black is at its most black point, but if you turn the black down too much, interference on the blue really starts to come back and starts to lose sync etc.

I'm now thinking towards cutting the MHz feed to the TIA and adding in some 33R to see the interference reduces or not...

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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: 2600 Composite mod

Post by PhilC »

Looks pretty cleaar as it is though
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