Display issue

Modding and Technical Issues

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srowe
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Re: Display issue

Postby srowe » Wed Jan 17, 2018 2:32 pm

Replacing the VIC resolves the majority of the problems on my CR test rig but the picture quality still seems inferior to my two pin system. Could someone summarize just what the circuit changes were to the CR and why they give a worse picture?

norm8332
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Re: Display issue

Postby norm8332 » Wed Jan 17, 2018 6:51 pm

This won't answer your question but it is clear that on the CR VIC they went over the entire design to reduce the cost by change of physical design, component elimination and using lower cost components. So in regards to the video output circuitry it appears they "downgraded" the video out amplifier from a more refined and accurate design to a simpler less accurate design with a lower part count. They also switched from top-tier component suppliers to lower-tier suppliers or lower model components of the same supplier..In other words cheaper components. This is across the entire board and all components except some of the chips.

I believe their belief at the time was: Get it as cheap as possible to produce as long as it's "good enough".

That said, it may be possible to mod the circuit for a better picture..I don't know if anyone has tried though.

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srowe
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Re: Display issue

Postby srowe » Thu Jan 18, 2018 2:23 pm

Thanks, that does seem to be the case. It's a shame as the VIC display was so much better than many other machines of its time. It was reasonable to stop using sockets and replace 2114s with 2K RAM, I can't imagine they saved that much on a handful of resistors and capacitors in the video circuitry but I guess every cent counted.

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srowe
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Re: Display issue

Postby srowe » Thu Jan 18, 2018 2:25 pm

norm8332 wrote:That said, it may be possible to mod the circuit for a better picture..I don't know if anyone has tried though.


I guess the S-Video mod would greatly improve it, but I don't have a TV with S-Video in.

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tokra
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Re: Display issue

Postby tokra » Thu Jan 18, 2018 3:34 pm

In my experience, doing the S-Video mod and then using a small S-Video -> Composite adapter gives a better picture than the native Composite-signal of the VIC. Or you could look for an S-Video to RGB adapter.


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