Trying to convert a Zenith SR2768S to take RBG,Sync,Ground

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PacManPlus
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Trying to convert a Zenith SR2768S to take RBG,Sync,Ground

Post by PacManPlus »

Hi everyone...

I apologize in advance for this...

Hopefully someone can help me. I have a Zenith SR2768S that I'm trying to convert to RGB use for some arcade boards (Pac-Man mostly), and I'm running into issues.
I've watched the 8-Bit guy's video regarding the Samsung, and I was able to get the 13" TV working like he has it. I use that one for testing boards, as there's so much overscan I can't do anything else with it (I tried all of the adjustments, couldn't alter the horizontal width - but that's a story for another time).

This 27" I'm looking to build a cocktail table around so I'm trying to convert it to RGB only. Don't care about any other input, as it will be dedicated.

This unit has *three* chips on the board that I cannot find any info about:

Sanyo 5LD7 LA76721 ( This is the only chip I found any kind of Datasheet on: https://www.alldatasheet.com/datasheet- ... A7672.html )
- The manual calls this the Video and IF Processor - IC1200
- I am assuming this is the Jungle Chip

Sony CXA1264AS
- The manual calls this the IC MTS Stereo Decoder / Audio - IC1400 (I assume this one isn't needed as I think it's only audio)

ITT G 044322 / 221-00947-01
- The manual calls this the Tuning Micro - IC6000

The manual itself doesn't have a schematic. I'm just looking for the RGB (and blanking) signal to intercept, as I'm using the composite input for sync and ground. The ground from the composite is tied to the ground for R,G,and B.

I tried plugging in sync via composite, and tying RED to pins 15, then 16, then 18, and then 19 on the Sanyo chip (I wasn't sure if I wanted in or out on this chip) - but none gave a good "red only" picture. I could barely make out the image, but it was so... for lack of a better word... LOUD... almost over-driven... So I tried attaching a 2.2K resistor at the end of the wire before trying the pins again (got the idea from another video I watched)... but that didn't seem to help.

I've been researching, watching videos - and of course being that all TVs are different, none of them even came close to what I have.
Please, I really hope someone can help me. The TV is apart in my garage, and I'm not sure where to go from here.

Thank you so much,
Bob
KPackratt2k
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Re: Trying to convert a Zenith SR2768S to take RBG,Sync,Grou

Post by KPackratt2k »

If that datasheet is anything to go by, I'm afraid the jungle chip in this set is Digital RGB only. According to the diagram, there are no clamping capacitors on the RGB line which is one way to tell. The voltages specified for the RGB lines also match up with another Sanyo jungle chip that is confirmed to be digital only. When attempting to inject an Analog RGB signal into a Digital RGB jungle chip, you will get an image with only 8 colors (best case scenario).

If this is indeed the case, then you're best bet would be to leave this TV alone and find a different one that has an Analog RGB input on its jungle chip. Neckboard modding is a possibility, but it's too complicated and risky to the point where it's not worth it in the end.
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PacManPlus
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Location: SW Florida, USA

Re: Trying to convert a Zenith SR2768S to take RBG,Sync,Grou

Post by PacManPlus »

Damn. :(

Ok, thank you so much for replying
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PacManPlus
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Location: SW Florida, USA

Re: Trying to convert a Zenith SR2768S to take RBG,Sync,Grou

Post by PacManPlus »

Just to double-check one last thing (please)...

What if I didn't care about any existing connections; I just want this to be an RGB 'arcade' monitor and nothing else... Does that make a difference?
I see people trying to keep their existing connections, but I won't be doing that here.

(Only asking because I actually *paid* for this TV, not knowing that this mod couldn't be done on some TVs) :(

Pictures of the boards are below:
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