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Better Picture Quality

MikeWMikeW
edited June 2012 in Hardware
Today I built a PSU and RGB-SCART monitor cable for my +3. However, I'm not too happy with the picture quality. It appears that there's like halos aound everyything. It does the same on my +3 and +2A...

Can anyone suggest what's cauging this:

IMG_0156.JPG
IMG_0157.JPG
IMG_0158.JPG
Post edited by MikeW on

Comments

  • ingoingo
    edited June 2012
    This might be a function of your monitor that enhances the edges of the signal. Maybe it can be reduced a bit by adding small capacitors (33pF to 1nF) from the r, g, and b line of the scart cable.
    I hade a similar effect using a scan converter from CGA to VGA (means RGB to VGA). I added resistors and capacitors, see here:
    https://fotoalbum.web.de/ui/external/p4tTSRKAS-eeSKwvxXo7BQ59303/0

    The special 15 pin plug is not important for you (it is from the converter) but the parts in the rgb lines.
    Maybe this could also help in your case.

    Regards Ingo.
  • bversteebverstee
    edited June 2012
    It looks like composite video, for which I made the document in this topic:
    http://www.worldofspectrum.org/forums/showthread.php?t=37695.
    Distorted composite video is mainly caused by the audio signal that is added to it.

    But the +3 does not have composite video on the RGB socket, so I doubt that is the reason.
    You should have very crips picture.
    But I also see some shadowing. That should really not happen with RGB.
  • MikeWMikeW
    edited June 2012
    I thought it might be my monitor too - I'd expect ghosting to be to the right of the image whereas my problem appears before as well as after the image. So I thought I'd move the +3 downstairs and try it on the 60" plasma:

    IMG_0159.JPG
    IMG_0160.JPG

    Things look a whole lot worse with a 5ft screen...

    Mike
  • bversteebverstee
    edited June 2012
    Looks like problems with the circuit within the SCART cable.
  • ingoingo
    edited June 2012
    You should try to insert the resistors/capacitors I mentioned above maybe also in the sync line.
    Modern TVs have some problems with the non standard spectrum video signal.
    Additionally when they expect PAL sources they await smeared picture with loss at high frequencies. Special calculation is done to "improve" picture quality. Sources with fast edges in signal may irritate that circuitry.

    Greets Ingo.
  • BiNMaNBiNMaN
    edited June 2012
    hmmm I had the exact same problem with my LG lcd, +2a/3 looks like that but toastrack and grey +2 look fine (perhaps because they have a composite signal?) soi bought a panasonic viera plasma set and they all look perfect so in my limited capaciy I think it's your tv. How does it look on a crt?
  • guesserguesser
    edited June 2012
    it has to be something in the TV, there's no way that the speccy is outputting that. I would check that you are getting the correct voltages out of the scart cable for each connection (video, blanking and sync pins).

    The white halo on the first TV makes me think the R,G, and B lines aren't in spec, on the second tv I suspect it's not happy with the sync pulses.
    My rubbish website including the redrawn Amstrad schematics and the Sinclair Wiki.
  • MikeWMikeW
    edited June 2012
    I think the first pics, it's the monitor too now. If I blow up the pics, you can see that the halo is on the preceding and proceding scanlines - it's gotta be some kind of post processing:

    IMG_0161.JPG

    Why it won't work on the big telly, I don't know...
    BiNMaN wrote: »
    hmmm I had the exact same problem with my LG lcd

    Incidently, the 60" is an LG plasma - maybe there's something in LGs firmware that doesn't like the +2A/+3 ?
  • MikeWMikeW
    edited June 2012
    Right, it's definitely some kind of image processing in the TV. It does exactly the same thing on a Commie, using an S-Video cable I just made...

    IMG_0162.JPG

    I'll try the low pass filter on the RGB lines to see if I can trick it a little.
  • BiNMaNBiNMaN
    edited June 2012
    MikeW wrote: »
    I think the first pics, it's the monitor too now. If I blow up the pics, you can see that the halo is on the preceding and proceding scanlines - it's gotta be some kind of post processing:

    IMG_0161.JPG

    Why it won't work on the big telly, I don't know...



    Incidently, the 60" is an LG plasma - maybe there's something in LGs firmware that doesn't like the +2A/+3 ?

    might be as the the +2a/b/3 pump out only rgb (although you could mod it for composite), perhaps the inclusion of the composite on the toastrack/grey+2 makes all the difference, I'm not as tech savvy as say guesser et al but 'I'm definatley' 99% sure it's the tv

    daft thing is the 'halo' effect looks like an rf signal sooo it could be argued that it looks more retro than having a perfect picture
  • ikciikci
    edited June 2012
    deleted and moved here --> http://www.worldofspectrum.org/forums/showthread.php?t=39709
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