French coleco with SCART

[cdn2a]

Does anyone have a circuit diagram of the french colecovision? I notice it has a SCART output. I'm interested for research purposes.

[cdn2a]

So no one?

[CrazyBoss]

if you want to mod your colecovision to have rgb output I think it might be easier to look what people did on Memotech and MSX, they use same VDP by the way

 

Some people said the TMS9918 dont output RGB, so another kind of ic have to help to convert to RGB. The TMS9928 do have RGB output on the VDP.

 

I just read it somewhere dont know if its right.

 

But maybe its better to go for the HDMI mod ?

[Tursi]

I can't talk to the SCART Coleco, but to CrazyBoss's post, the 9918 outputs composite video, which can't be trivially converted to RGB (and won't look any better anyway). I don't believe ColecoVisions use the 9918 anywhere (just the 9928 and 9929)?

 

The 9928 outputs a form of component video that can be converted by a circuit to RGB, as does the European 9929. Any of those can also be replaced by an F18A which gives VGA out.

 

As for how the SCART is wired internally, though, I'd be curious to see that too.

[cdn2a]

Ok,

 

So I will confirm this for some people.

 

https://en.wikipedia.org/wiki/Texas_Instruments_TMS9918

The NTSC TMS9918 does output composite video.

 

The question no one is asking is HOW.

So let me clarify, it uses pins 35,36,38 to create a composite signal. That is then modulated to become RF out.

The chip outputs what is known as "YUV". And yes, it is actually TRIVIAL to convert to RGB.

 

All it takes is an LM1881 "sync stripper" and a high speed amp.

See here for a schematic. http://www.labguysworld.com/YUV2RGB_Matrix.htm

 

The reason I was interested in the SCART schematic, was I was interested in how the amp in the CBS version was built.

 

As an aside, (I have parts on order to test theory), I believe it might be possible to convert the NTSC Coleco

to HDMI for less that $40. (I know, outrageous claim... but 5-11 already did part of the legwork...)

 

If it works I can post a video on how it works, for those that are interested.

[Tursi]

CDN2A -- the TMS9918A outputs composite video directly from the IC on pin 36. The (US) ColecoVision doesn't use the TMS9918A, it uses the TMS9928A (PAL uses the TMS9929A), which functions as you describe. Datasheet attached.

 

 

9918a28a29a.pdf

[+5-11under]

All it takes is an LM1881 "sync stripper" and a high speed amp.

See here for a schematic. http://www.labguysworld.com/YUV2RGB_Matrix.htm

 

Thanks for the link. It explains the LM1881 quite nicely.

[cdn2a]

Tursi,

 

Sorry, your right, I meant 9928 vs 9929.

 

The long and short of it is, 9929 is RGB, we all know that. Swap the chip, and you have RGB.

The 9928 is YUV.... which is actually the same as... YPbPr the analog version of YCbCr...

 

With the previous work that has been done before, 5-11 built a board, to output YPbPr (component).

 

However with my experiments, I can confirm, the "blue" is very slightly out of phase with the other 2

signals. Which is why there is a blue tinge to the black color in the picture.

 

Using a pot, trim the blue output by about 92ohms and the tinge is gone.

I'm waiting for this....

 

http://www.ebay.com/itm/141913950282?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

Wire pins 35,36,38 and ground and +5, and one should have a very cheap but effective HDMI out....

 

All connections would be direct, (Except for pin 35 to Pb, it would need a 100ohm trim pot)