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Mister Fab

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Posts posted by Mister Fab

  1. Posted

    At this point, my skills in electronics are just too low compared to yours, but I'll try to be good at drawing and to be the most accurate I can to finish to copy the circuit without any errors. It will take some time. I have nearly finished the back side. The component side is a bit tricky due to the tracks running under the large ICs.

  3. Posted

    1 hour ago, ChildOfCv said:

    Well, you've partially answered my question anyway :)  C156 and C156A have negative pole connected to pin 4.  Okay, looking at the schematic in progress again, I can see that.

     

    There's a large ground rail that goes in a horseshoe pattern under the PCB which connects several pins.  I thought it might do that and come back up on top at that leftmost pad.

     

    And you confirmed that U29 pin 6 connect to the collector of (omitted transistor) Q26?

     

    So the Y signal controls Q23, which controls the U29 pin 6 net and goes to the sync detector/amplifier.  I think the purpose here is to mute the color signals during sync periods, but would have to see it in action to confirm that.

    Looks like I now have a use for C140 too.

    1 hour ago, ChildOfCv said:

     

     

    And you confirmed that U29 pin 6 connect to the collector of (omitted transistor) Q26?

     

    Yes, I confirm. It should have been Q26

     

  4. Posted · Edited by Mister Fab

    2 hours ago, ChildOfCv said:

    Could you recheck U29 pin 4?  It now shows a connection to ground at the capacitor.  I think that instead, the capacitor connects to the via that horeshoes between the ground points underneath.  This leaves room for U29 pin 4 to reach Q26/Q23.  And I suspect that U29 pin 6 goes to AV pin 7 also.

    I just rechecked pin 4, I don't get any continuity signal with any pin of AV connector.

     

    I get a continuity signal between U29 pin 4 and C156 negative, and on the other side to C147

     

    Sorry, I don't understand the green part I underlined in your comment.

  6. Posted · Edited by Mister Fab

    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

  10. Posted

    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

  12. Posted · Edited by Mister Fab

    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

     

     

     

  14. Posted

    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?

     

     

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