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-^Cro§Bow^-

UAV - Ultimate Atari Video - Atari 7800

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Are people saving the RF modulators to repair 7800s in the future? I ran into that on a Coleco that needs the RF to work to Mod the video. No RF = no video.

 

Well in the case of the 7800, the RF modulator isn't needed at all for the AV mods that exist for it. Having said that I do usually keep the RF modulators in place and working when I've done AV mods on the 7800 for clients. I've got a few of the 7800 RF modulators saved and on hand from those that didn't want them though on hand. I also save the RF modulators from 5200s when I've been requested to remove those doing AV mods.

 

But you are correct in that the standard composite AV mods for the CV do require the RF modulator to be somewhat functional. I guess only the FA18 mod wouldn't car since that completely replaces the video circuitry in the process.

Edited by -^Cro§Bow^-

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Well in the case of the 7800, the RF modulator isn't needed at all for the AV mods that exist for it. Having said that I do usually keep the RF modulators in place and working when I've done AV mods on the 7800 for clients. I've got a few of the 7800 RF modulators saved and on hand from those that didn't want them though on hand. I also save the RF modulators from 5200s when I've been requested to remove those doing AV mods.

 

But you are correct in that the standard composite AV mods for the CV do require the RF modulator to be somewhat functional. I guess only the FA18 mod wouldn't car since that completely replaces the video circuitry in the process.

 

I wonder if some of the UAV could be used to completely replace the modulator for the CV though? After the analog switch you get Y, Pb, and Pr, which can *almost* be sent directly to the component input on TVs that have it (you just get a bluish hue for everything due to the TMS method of inducing color burst). But if the chip that he uses takes those inputs directly, it could work.

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So here's something:

 

UAV video looks great, except... Some 2600 games have rolling horizontal bars. H.E.R.O. in particular has them really bad, completely distracting. Other 2600 games are completely fine and have no rolling bars.

 

7800 games don't appear to have them at all, and even if I turn the TV's brightness all the way up - they are barely perceptible. - but this same 7800 had no rolling bars when it had a standard two resistor/transistor mod in it. (although it had other distracting interference.

 

What say ye?

 

New Caps? (already changed the 7805 VR) Something wonky in HERO?

 

For an example this is what I'm seeing (not my video but same thing):

 

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Well, it's not an issue with the HERO game or PCB itself - my copy is fine in through my 7800 and UAV:

 

post-30400-0-78558800-1559867589_thumb.jpg

 

post-30400-0-45266200-1559867602_thumb.jpg

 

 

It's possible you have a grounding issue with the TIA color pot, perhaps. Other 2600-specific causes might be bad connections at one or more of the TIA luma pins, or the TIA Color signal into the UAV. If your TIA is socketed you might try removing and reseating it.

 

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Well, it's not an issue with the HERO game or PCB itself - my copy is fine in through my 7800 and UAV:

 

IMG_1617.JPG

 

IMG_1619.JPG

 

 

It's possible you have a grounding issue with the TIA color pot, perhaps. Other 2600-specific causes might be bad connections at one or more of the TIA luma pins, or the TIA Color signal into the UAV. If your TIA is socketed you might try removing and reseating it.

 

heh. Figured it out.

 

Took the whole damn thing apart at work and re-soldered all the joints to the various access points on the motherboard just before the resistor ladder and it looked gorgeous on a spare TV we have laying around the office.

 

Took it home... whomp whomp. Same issue. Then I remembered - it's going through a component video switchbox to the tv because the TV only has one composite input and no S-Video.

 

Plugged it in directly - perfect. So it was my shitty radio shack switcher introducing interference, not the 7800.

 

Funny thing is - my Sega Genesis and Master System both also go through that switchbox, and do not have the rolling bars, but they are also standard spec composite video, not modded - right out of the 6 pin DIN port.

 

Now I have to try to re-situate the switchbox somewhere it won't get interference, or just junk it and deal with swapping cables when I want to switch consoles.

 

Thanks for the help, all!

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