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New Coleco RGB board?

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5 hours ago, Mister Fab said:

Hi all,

I just found this topic while searching a way to modify my Colecovision.

 

I got the console when it came out it france in 1983. So it is a  PAL RGB / SCART version

 

It was still working on my 2013 Samsung 55" smart TV, as there were a SCART connector on it, but I just replaced my TV for a Philips 65", and no more SCART on it.

 

I bought an OSSC 1.6, which works perfectly with RGB SNES (after I modified the AV cable to use Luma sync )

 

But when I connect the Coleco, I can get sound, the OSSC shows a sync but I can't get an image.

 

It seems the Coleco only has C-sync which is not compatible with OSSC.

 

Has someone already faced that case?

 

 

https://www.retrorgb.com/frenchrgbconsoles.html This might help you out a bit and is what the people on the OSSC board were talking about (I think) in regards to it might not be true RGB out of the console and just composite converted to RGB, which the OSSC does not like

Edited by zaphro72
accuracy

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Doesn't the SECAM version still use the 9929 though?  Its output is analog Y, Pb, and Pr, almost directly compatible with component video output other than a burp at the color burst.  The Citrus board then does the necessary summing to get RGB and sync.  So in theory, since you're getting video before the modulator, the nature of the modulator should be irrelevant.

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image.thumb.png.629e57a68ffaf0071b7c615158416e00.png

 

 

These are the two "official" wirings I have found on Colecovision.dk

 

I checked my working cable (tested on a cathodic TV) with a ohmmeter, and here's what I got:

 

image.png.d50d8e7fbef90947adbe1558c388911c.png

 

Pin 4 and 5 (orange and black wires) are inverted on the DB15 side if I compare to the official wirings, and I can't understand how RGB blue and +12V can be inverted.

 

I tested the voltage on scart pin 8, I get 12V as it should be.

 

When I plug the cable to the OSSC, I get this on the screen, but black screen out:

 

image.png.78f5b528bd3f63c59776df8b6490f66f.png

 

 

 

Edited by Mister Fab

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Here are two hi resolution pics of the motherboard (91209 rev.B)

 

img_2013.jpg

 

 

img_2014.jpg

 

 

Edited by Mister Fab

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Cool, though I was thinking about the situation of using the Citrus3000Psi add-on and going through that.  I had forgotten that they have SCART out (isn't there an old version that actually modulates TV output?)

 

Anyway, I can see from first glance that the board has the YPbPr to RGB summing networks and amplifiers for the signals, but I'll have to map it out to figure out what it does with sync, and where everything goes.  Fun!

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On 1/29/2020 at 5:50 AM, Mister Fab said:

Pin 4 and 5 (orange and black wires) are inverted on the DB15 side if I compare to the official wirings, and I can't understand how RGB blue and +12V can be inverted.

Well, preliminary work shows that there's definitely a power trace going to pin 4 on the PCB.  So either these sites are wrong, or there are different pinouts for different revisions.  Another note is that pins 6, 8, and 14 are connected, possibly to that fat ground trace that burrows underneath from the right.

 

BTW, if you could get a picture on the other side of that trimmer resistor so that I can see the traces there, that would be great.

 

scart.thumb.png.b0ad1d0013d9f1d411b49a09829a56c0.png

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Wow!! you impress me ChildOfCv!!

 

Just to say, I practice electronics, but I have limited knowledge.

But if you need any signal test, I have an oscilloscope, so if you tell me where to test I can give you all the results.

 

I will take very detailed pictures this afternoon

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Here are the pics, I took quarter by quarter of the board. Tell me if you need more details.

 

img_2015.jpg

 

img_2016.jpg

 

img_2017.jpg

 

img_2020.jpg

 

img_2019.jpg

 

img_2018.jpg

 

img_2021.jpg

 

img_2022.jpg

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So, pin 10 is +5V and pin 2 is +5V through a 160-ohm resistor.

 

One thing I need is the part number of those transistors.  Many are MPSA13, but there are others that I can't read, and I'm sure at least some of them are PNP.

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U29 and U30 (the 4066 analog switches), are pins 5, 6, and 13 all connected between the two of them?  (Are any of them?  🙃)

 

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So, here's the probable pinout:

1 - Red

2 - +5V (160 ohms)

3 - Green

4 - +12V

5 - Blue

6 - Gnd

7 - Amplified audio?

8 - Gnd

9 - R-Y component

10 - +5V

11 - B-Y component

12 - unknown (possibly unconnected)

13 - Y component

14 - Gnd

15 - Unamplified audio

 

Here's a rough schematic that probably bears some resemblance to the actual circuit

scart.thumb.png.5f226eee3aaf4d44cce15b819c27221f.png

 

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So you preferably need a sync separator before the OSSC input.

Worth a try. (see the ready to use "syncblaster" which has the proper 75ohm output level).

 

And it would be perfectly coherent for why it work on a "normal" TV but not on the OSSC as a normal TV have the CSYNC imput common with the CVIDEO input.

Edited by emmanuelf
sync blaster

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Is is astounding to see how clean and modern is the design of the console and the PCB for the time being.  And mainly done by one man.

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Hi,

I'll send tomorrow the pcb on both sides, I had some time today to draw it from the board on several layers with paint.net.

Still in progress, but I hope it will help.

 

 

image.thumb.png.54f10a3c01dafddd5d2cd7c6dbe61ad1.png

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Some more interesting info:

On NTSC boards, pins 41 and 42 on the expansion board are unconnected.  Pins 31, 32, and 33 are external audio, external video enable, and external video composite.  The SECAM board changes all of that.

 

Pin 41 is now external audio.  42 is external video enable.  Pins 31, 32, and 33 are the YPbPr signals.  So the SECAM Expansion Module 1, if it exists, apparently has much better video than the NTSC one does.  And likely leagues better than the Atari 2600 SECAM.

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2 hours ago, Mister Fab said:

@ChildOfCv, there's no pnp transistor, only npn.

 

F2N3904

F2N3906

MPSA13

3906 is PNP :)

 

More importantly, impressive work mapping those traces.  Especially underneath the connector and ICs.  I had to do a lot of puzzling, process of elimination, and outright guessing.

 

I see that one of the traces seems to abruptly end underneath the connector though.  Have you just not found its destination?  It may be connecting to one of the two vias that come up underneath.  Here's a closeup of that area with my doodles.  The two red dots are the vias.

scart.thumb.png.34685de329c6bb613bdc99e4fc7e7568.png

Edited by ChildOfCv

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9 hours ago, emmanuelf said:

So you preferably need a sync separator before the OSSC input.

Worth a try. (see the ready to use "syncblaster" which has the proper 75ohm output level).

 

And it would be perfectly coherent for why it work on a "normal" TV but not on the OSSC as a normal TV have the CSYNC imput common with the CVIDEO input.

Well, after reconciling a few things with Mister Fab's awesome efforts, I think even that may not be necessary.  That amp on pin 7 seemed odd, and after reconciling the fact that pin 15 does not mix with it, I'm now convinced that this is the CSYNC generator.  So here's a PDF based on the combined effort.  Pinout is included near the connector.

 

VideoMultiplexer-A-V Multiplexer.pdf

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One more thing:  I have U29 pin 6 and U30 pins 6,5, and 13 connected, but nothing to drive them.  Could you check if they're connected to pin 7, or possibly to Q24 directly?

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10 hours ago, ChildOfCv said:

Some more interesting info:

On NTSC boards, pins 41 and 42 on the expansion board are unconnected.  Pins 31, 32, and 33 are external audio, external video enable, and external video composite.  The SECAM board changes all of that.

 

Pin 41 is now external audio.  42 is external video enable.  Pins 31, 32, and 33 are the YPbPr signals.  So the SECAM Expansion Module 1, if it exists, apparently has much better video than the NTSC one does.  And likely leagues better than the Atari 2600 SECAM.

Ok mysterious difference between the RGB version for the SECAM market and the others are no longer mysterious. The adaptation needed for the super game module is now obvious.

Yes Expansion Module #1 exist and is specific to this model. Beside the same adaptation for external sound, that explain the "no sound/no picture" when PAL or NTSC Expansion Module #1 is plugged into a RGB model.

How things are done in #1 remain to be seen. A YPbPr TIA clone ? I will open one and take pictures.

 

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Hi guys,

 

I continued my work on the other side of the board. I didn't map the full board for now, but I'll continue to finish the full board, hoping it can be usefull to someone in the future.

 

I will shrare the paint.net file when I'll have finished, it is easier to hide each layer when looking for something particular.

 

I made a few modification on the component side to the tracks under the A/V connector, I found some errors while I started to map the back side.

 

Let me know if you see some incoherences so I can correct them.

 

 

front.jpg

back.jpg

Components + tracks.jpg

Components.jpg

Edited by Mister Fab

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I took a picture of each transistor, I think I didn't make a mistake about they're all npn. Aren't collector and base inverted on pnp?

 

image.png.fb81a6a1ad301d39426966b73caf4fe6.png

 

image.png.3c4e3d4b2d7e1dcf1c206deaf77eabac.png

 

image.png.fa18fc183e62c59999703203fd0bb06c.png

Edited by Mister Fab

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