Weird color issue

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  • #24175
    Zarper
    Participant

    I’m having some color issues with my new OSSC.
    On the AV1 port the picture looks fine when using RGBS 15 kHz and YPbPr above 15 kHz. But when I use RGsB above 15 kHz I get a yellow tint on the picture and with YPbPr 15kHz I get a blueish tint.
    The OSSC is set to the correct input, so it is not a YUV/RGB mismatch. AV2 works correctly with YPbPr with all resolutions I’ve tested (480i-1080p).
    The sources I’ve been using is a PS2 and a PS3 and they both act the same. However, I only have one SCART RGB cable. But if the cable works correctly with RGBS and YPbPr above 15kHz that shouldn’t be the issue, or could it?

    Is there anything else I can test?

    Any suggestions would be appreciated.

    #24204
    Zarper
    Participant

    I took a few pictures to illustrate the issue. The yellow tint isn’t as noticeable on the test image as in other places, but you can see that white isn’t really white.
    It seems to me as the B/Pb channel isn’t able to go above 50% intensity.

    #24206
    paulb_nl
    Participant

    If there are capacitors in the SCART head then try to remove them. They are only needed with PS1.

    If that does not work then you should try another cable.

    #24207
    Zarper
    Participant

    It’s a PS2 cable and should not have any capacitors. And wouldn’t that mess with all outputs equally?

    #24218
    BuckoA51
    Keymaster

    It does seem unlikely to be the cable but I guess it is possible, it’s not one of the old “boosted sync” cables or anything strange like that is it?

    #24225
    Zarper
    Participant

    It’s a ~6 months old Retro Gaming Cables PlayStation 2 RGB SCART PACKAPUNCH PRO with sync on luma.

    I remembered that I have an old Xbox Advanced SCART cable. I’m going to switch that over to output YPbPr instead. That way I can at least test AV1 YPbPr with another cable. There is a way to make the Xbox output RGsB, but I don’t feel like messing with that if I don’t need to.

    #24229
    BuckoA51
    Keymaster

    Ok great please let me know what you find.

    #24235
    Zarper
    Participant

    So, I tested the converted cable, except for the picture quality being really bad, the colour was fine no matter what resolution I tried.

    I then decided to convert a composite+stereo to SCART adapter into a RGB RCA to SCART adapter and tried on both a Xbox and a Xbox 360. Everything looked great. So unless there’s a difference between Sony’s and Microsoft’s YPbPr signal, it has to be the cable.

    Can’t quite grasp how a straight copper cable can work with some resolutions and encodings and not others. Is there a good way to measure the blue channel to get a definitive reading?

    #24236
    paulb_nl
    Participant

    Maybe a short to ground in the cable is causing this?

    #24237
    Zarper
    Participant

    If it really is nothing but a straight copper wire, I guess that or some damage/bad connection is the only solution. But the picture is completely stable and the issue is consistent. And why on certain resolutions and encodings and not others? If it at least had been the high bandwidth signals.

    #24238
    Steo
    Participant

    I have the exact same cable as you (Packapunch Pro Luma Sync) and my PS2/PS3 don’t have that issue. I did have a similar issue before when I played my Jaguar on a CRT, but the colours were fine on the OSSC. Turns out it was outputting TTL sync levels and it needed a capacitor and resistor on the sync line, after I did this, the colours were correct on the CRT and I wasn’t afraid of breaking my OSSC.

    I know RGsB is different though and we have the same cables, so it is pretty unusual. I was going to say I have a multimeter there if you want me to test mine, but if it’s just copper wire with nothing along it’s path, then there’s nothing that can be different really.

    #24242
    Zarper
    Participant

    I feel a bit stupid now, but I’ve confirmed it’s the cable. There is a short between blue and sync and a slight short (600-800 kOhm) to red.
    When I buy cheap cables from China I usually measure them before usage, but I figured there was no need this time. Also, the symptoms seemed way too complex to be a simple short, still don’t understand how this wouldn’t affect all output more, shows what I know.

    Anyway, thanks for all the help.

    #24244
    Steo
    Participant

    I was the same with my Jaguar, I thought the RGB on the console itself was messed up at first until it was the right colour on the OSSC. I guess we just assume that these things are going to work as expected so it’s not really our fault.

    Anyway, it’s nice that you could figure out the issue. 🙂

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