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Two 22nf caps factory added on the RF?


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#1 Shawn OFFLINE  

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Posted Wed Feb 13, 2019 12:36 AM

Hey All,

 

Found something I had not seen before while modding a 7800 tonight. The RF box has 2x 203 caps installed on the outside! I'm 99.9 percent sure I'm the only person who has ever opened up this machine too. They are the same flavor Atari used as well so it seems these where added by Atari. I have no clue why these are on there. The RF jack was loose so it was a no brainer to do an AV mod on this unit but man was I surprised with this find while removing the RF box. I've probably opened up a good 50 different 7800 machines over the years and this is a first. Anyone else ever seen this done? Anyone know what the purpose is? I was playing with the idea of smoothing the voltage but it's got 2 of them and they go from 5V to the channel select and then to ground. Even if it was for power smoothing I would assume a .1uf cap not two 20 nf caps.

 

DSCF8951.JPG

 

 

Shawn



#2 Shawn OFFLINE  

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Posted Thu Feb 14, 2019 10:38 AM

Wanna see what that RF PCB looks like now? It morphed into a composite & simulated Svideo board :P

 

DSCF8961.JPG



#3 John Stamos Mullet OFFLINE  

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Posted Thu Feb 14, 2019 10:54 AM

which serial number series is it? A1, A3, X, or 1984?



#4 -^CrožBow^- OFFLINE  

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Posted Thu Feb 14, 2019 11:32 AM

Wanna see what that RF PCB looks like now? It morphed into a composite & simulated Svideo board :P

Simulated S-vid? 



#5 SmittyB OFFLINE  

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Posted Thu Feb 14, 2019 11:59 AM

Simulated S-vid? 


If you poke yourself in the left eye and close your right it simulates RF. Close your left eye and open your right then ta-da! Simulated S-video.

Combine that with shifting heavy furniture for the full SCART experience.

#6 -^CrožBow^- OFFLINE  

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Posted Thu Feb 14, 2019 1:21 PM

If you poke yourself in the left eye and close your right it simulates RF. Close your left eye and open your right then ta-da! Simulated S-video.

Combine that with shifting heavy furniture for the full SCART experience.

O_0

 

Oh okay..it was a joke and I didn't know it kinda thing...gotcha. I do have a few spare ready made Magic Knight PCBs made up with audio filtering corrected on them now. So he doesn't have to have a "simulated" experience...



#7 SmittyB OFFLINE  

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Posted Thu Feb 14, 2019 1:34 PM

I don't know what simulated S-VIDEO is. I just wrote what I figured it would take to simulate the experience.

#8 Shawn OFFLINE  

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Posted Thu Feb 14, 2019 2:42 PM

Simulated S-vid? 

 

http://www.epanorama...deo2cvideo.html



#9 Shawn OFFLINE  

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Posted Thu Feb 14, 2019 2:42 PM

which serial number series is it? A1, A3, X, or 1984?

 

A1 with expansion connector.



#10 -^CrožBow^- OFFLINE  

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Posted Thu Feb 14, 2019 2:49 PM

 

A1 with expansion connector.

 

So you are doing the opposite and filtering the chroma and luma back out of the composite video? I had an old TG-16 s-video circuit that did the same thing. Produced horrible checkerboarding and still was a tad fuzzy overall on the image. 



#11 Shawn OFFLINE  

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Posted Thu Feb 14, 2019 3:45 PM

 

So you are doing the opposite and filtering the chroma and luma back out of the composite video? I had an old TG-16 s-video circuit that did the same thing. Produced horrible checkerboarding and still was a tad fuzzy overall on the image. 

 

It's decent enough on most TV's I've used it with. Some have had jailbars like on my Sony Bravia others have had a nice picture like on my Plasma JVC. Yes it can be fuzzy but if you have a TV without a composite connection and only Svideo for some reason it's there as an alternative to the composite.

 

 

 

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