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New Coleco RGB board?

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4 hours ago, emmanuelf said:

If you're using this as a way to disagree with me, I will quote from the first paragraph:

"This glassware equals or exceeds the finest crystal in lead content and comes very close to being defect free in both contaminant-induced artifacts and optical properties."

You're citing general info about CRTs used for televisions, which have a different materials construction from monitor tubes (and is shown in the materials used in monochrome CRTs.

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Most color CRT front panel are lead free as you could see in this document and the radiation problem is on the back of the tube which is leaded and coated. But it is nitpick anyway ....

 

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That's the "Hackaday" circuit in this comparison back on page 14. :D

 

The sample-and-hold idea used in TMS-RGB comes from that one.  It had a great, original idea on how to solve the too-much-blue problem.

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1 hour ago, Falonn said:

That's the "Hackaday" circuit in this comparison back on page 14. :D

 

The sample-and-hold idea used in TMS-RGB comes from that one.  It had a great, original idea on how to solve the too-much-blue problem.

Sorry, I suspected you were very aware of this already.

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No need to be sorry.  The more I've investigated, the more I've found these things hiding in the cracks.  I only spotted this attempt from New Zealand a few weeks ago (where they had RGB output for the SC-3000 in mind instead of the Colecovision).  It looks like they went through a lot of the same steps as we did here, only three years ago.  I wouldn't be surprised if there were another half-dozen people that have worked on the same thing over the years.

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21 hours ago, Falonn said:

No need to be sorry.  The more I've investigated, the more I've found these things hiding in the cracks.  I only spotted this attempt from New Zealand a few weeks ago (where they had RGB output for the SC-3000 in mind instead of the Colecovision).  It looks like they went through a lot of the same steps as we did here, only three years ago.  I wouldn't be surprised if there were another half-dozen people that have worked on the same thing over the years.

Yeah, I've seen quite a few others over the years myself.  Many years ago I tried to build a ColecVision to component video mod based loosely on the "TMS9928/29 and TMS9128/29 Interface to Color Monitors" report.  While I got an image, I got the dreaded blue tint all over the screen.  As I didn't have a clue about what I was doing with analogue video signals, other than being handy with a soldering iron, I gave up.  At least I enjoyed the process 😀

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As a footnote: I went back and annotated the "TMS9928/29 and TMS9128/29 Interface to Color Monitors" document, otherwise known as the "TMS Doc" earlier in this thread.

 

This version highlights all (9!) known mistakes, including a new pair I only just discovered in the description of the blue channel conversion.  If we discover more, I'll keep it updated in the same place.

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Is there a difference between TMS9928anl and TMS9928an chips? Looking for a replacement chip and the original is an anl but the ones I’m finding cheap off eBay are only designated AN

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This is just a guess, since TI's suffix designations are a bit of voodoo that can mean anything from performance differences to how they are sold in bulk (tube, box, etc), but I know that the chips can come in either ceramic or plastic packaging.  Maybe the "L" means "pLastic".  Or maybe it means "Lead free", though that may not have been a concern during the chip's manufacturing lifetime.

Anyway, if the chips are cheap enough, it shouldn't be a huge concern to try one.  They all have the same pinout and respond to the same programming.

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