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Thread: Problem with RGB SCART TO YUV - SEGA Genesis

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    Road Rasher Qjimbo's Avatar
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    Default Problem with RGB SCART TO YUV - SEGA Genesis

    I recently purchased a Shinybow SB-2840 RGB SCART TO YUV Converter, so I could play Genesis games on my Sony KV-27FS120 CRT TV in better quality. Other converters I have seen on Amazon apparently have colour shifting problems, and this one outputs the audio which is cool. I tested the TV with 480i component from my Wii and that works.

    However, this is the result when I hook everything up with my SEGA Genesis - a grey picture that slowly wraps around.


    From what I understood this converter is supposed to just take the input and dump out the same resolution/format in YUV. Here it is hooked up (yes I'm using RCA cables for the YPbPr for now, but they do match).


    Any idea whats going on here? I think either the TV doesn't support 240p component, which doesn't make much sense since it works with composite and s-video just fine, or for some reason the box is upscaling it to 480p (the effect on the screen is very similar to when the TV gets a 480p signal), which the CRT doesn't support. But why wouldn't it upscale it to 480i? I know the box does work with 240p signals as there is a video on youtube of someone using one, which is actually why I thought this was a safe bet.

    UPDATE: I took it apart to look at the PCB to see if there was some big scaler chip or something, and there's nothing, don't think there's even a timing crystal. It looks actually as simple as I thought it was. Pictures below:
    http://i332.photobucket.com/albums/m...artyuvpcb1.jpg
    http://i332.photobucket.com/albums/m...artyuvpcb2.jpg
    Any way I can "hack" it to force 240p output, if that is the issue? Any other thoughts?
    Last edited by Qjimbo; 10-07-2014 at 09:03 PM.

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    urusei yatsura Master of Shinobi lumclaw's Avatar
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    It's common for HDTVs to accept 240p composite and s-video (even if they process it as 480i mistakenly), then fail with component.
    Never heard of a non-480p set doing that.

    In any case neither the converter or TV info I've seen mentions 240p.
    http://dutchmen.com/image/data/docum..._TV_Manual.pdf
    http://www.shinybow.eu/eshop/datasheed/SB-2840.pdf

    Does your RGB cable use c-sync or composite video? Might be something to try.

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    WCPO Agent roadkill's Avatar
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    Quote Originally Posted by lumclaw View Post
    It's common for HDTVs to accept 240p composite and s-video (even if they process it as 480i mistakenly), then fail with component.
    Never heard of a non-480p set doing that.
    Same here. I thought all CRT SDTVs that had component inputs accepted 240p signals without any issue. As for HDTVs only accepting 240p for composite and S-Video, and not for component, my 42 inch LCD HDTV is the same way.

    TC, you mentioned you tried your Wii on 480i, but did you try any Virtual Console games (NES/SNES/Genesis/TG16)? They will automatically switch to 240p if your Wii is set to 480i, and if you get a black screen then your TV doesn't accept 240p on component for sure.
    Last edited by roadkill; 10-08-2014 at 05:36 AM.

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    Road Rasher Qjimbo's Avatar
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    Unfortunately the (cheap) component cable I had for my Wii broke, so I'll gave to pick up another one before I can do that test - BUT I did just plug in the composite output into the green and that did show a stable B&W image (not sure why it wasn't green but its the same result as from a DVD player). I just did a test on a 720p LCD TV I had and that didn't read the signal so that is a good sign (its not upscaling) either that or the box is just outputting garbage.

    Not sure what sync the cable uses - I will take a look now.

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    Mastering your Systems Shining Hero TmEE's Avatar
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    Is this a "pure sync" SCART cable ? I think the problem is the sync line being overloaded. The sync line cannot drive a 75ohm load, the composhit signal can however.
    The box is an analog transcoder, it has no upscaling or other things going on, and also has no clue what signal you feed it nor it cares about the signal as long as drive requirements are met.
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    Road Rasher Qjimbo's Avatar
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    I FIXED IT! It *was* the sync!

    Turns out both the RED and SYNC wires had broken off inside my SCART cable.


    I resoldered that grey one to sync and the purple one back to red and now it works great! Not sure what that blue one is for, but haven't seen any issues without it so may just be a spare wire in the cable.

    So for the record, the Shinybow SB-2840 DOES work with 240p - beautifully in fact. I think the SCART cable is missing some capacitors or resistors which is making the image come in a little bright, but I can deal with that, just glad it's not the converter.


    Thanks for your help guys!
    Last edited by Qjimbo; 10-08-2014 at 02:24 PM.

  7. #7
    urusei yatsura Master of Shinobi lumclaw's Avatar
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    Quote Originally Posted by TmEE View Post
    Is this a "pure sync" SCART cable ? I think the problem is the sync line being overloaded. The sync line cannot drive a 75ohm load, the composhit signal can however.
    The box is an analog transcoder, it has no upscaling or other things going on, and also has no clue what signal you feed it nor it cares about the signal as long as drive requirements are met.
    Sounds about right. In theory boxes of this sort should have no issues at 480p or greater, with joined h-sync and v-sync.

    Don't recall it being seriously tested though.

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    Road Rasher Qjimbo's Avatar
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    Yeah I think that would work, in the manual it actually says it supports 480i/480p/720p/1080i/1080p, so the unit appears to be very versatile when it comes to resolution.

    Also as a side note I added some 75ohm resistors into my SCART cable as per the spec, and the image is perfect now (I also love that there's nothing I have to calibrate inside the unit, it just works)

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