› ›

s-video Success

dastephdasteph
edited April 2005 in Sinclair Miscellaneous
Having tried the various composite video fixes for the +3 etc, I was left feeling a little cold at the results, and was about to give up my quest for a decent image. That was until I found this site http://www.nexusuk.org/projects/rgb2svid/notes.php which contains all the details needed to construct an RGB to s-video converter.

Needless to say I went straight to work and constructed the interface (minus the LM1881), and the result is very impressive, not as clear as RGB of course but still 400% on RF video and at least 200% on the composite interfaces I'd built earlier.

You can find the schematic and PCB layout (Eagle CAD) I made here http://www.dasteph.com/svideo.zip The PCB fits comfortably inside my +2a and you should be able to find room in a +3 for it.

Obtain the RGB signals from the base of the Peritel connector.
CYNC should come from below resistor R34. (the signal at the Peritel is to weak)
Ground and +5v can be obtained from 2 VIA's next to the power connector.

The design also allows for a composite signal, just in case you want it.

I'll make some pics available if anybodies interested, once I find my digital camera.

[ This Message was edited by: dasteph on 2004-04-12 17:30 ]

[ This Message was edited by: dasteph on 2004-04-12 18:11 ]
Post edited by dasteph on

Comments

  • dastephdasteph
    edited April 2004
    OK here's a pic taken of the S-Video adaptor in action, http://www.dasteph.com/svid.jpg If you compare the image to those on the Spectrum 128 site you should get a rough idea of the quality http://www.fruitcake.plus.com/Sinclair/Spectrum128/SCARTCable/Spectrum128SCARTCable5.htm

    [ This Message was edited by: dasteph on 2004-04-14 15:18 ]
  • dastephdasteph
    edited January 2005
    Update to the S-video schematic, find new version here
    http://www.dasteph.com/svidschea.jpg

    New design has better filtering, and also works on russian clones. Device still needs to internal, but I'll post an external version latter.
  • AnestisAnestis
    edited January 2005
    I will try to build it as soon as I get back home after the 21 of January. I would like to try it with a VGABOX I have so I could use my +2 and +3 on a vga monitor.

    Cheers,
    Anestis
    As a young boy chasing dragons with my wooden sword so mighty
  • ADJBADJB
    edited January 2005
    Any chance you could do a dxf file of the layout ?

    ADJB
  • dastephdasteph
    edited January 2005
    Can't provide a dxf, but I'll put the full eagle cad (same thing really) file up over the weekend. Just have to make some changes to the layout first, as the current version got moded on the fly. Anyway hopefully by Sunday.
  • dastephdasteph
    edited April 2005
    OK so its a bit late but here is the final version of the s-video adaptor, both the schematic and board layout in the zip file are made in eagle cad.
    http://www.dasteph.com/zx2a/files/

    Some notes
    Follow the same instructions as previously mention above installation.
    C1, C2 and C3 are mains metallised polypropylene capacitors (image is everything), I found these to give the cleanest results. These could be replaced with high quality Green Caps is pushed.
    C19 is the most obvious change in the design, it's there to filter power waves, not so noticeable with the standard +2a wall wort, but if your using a modified old AT supply or similar its a must.

    I have tried to get an external version to work, but I've only had limited success, it all seems to come down to a problem with the csync signal provided at the Peritel connector. So unfortunately it's an inside job only.

    Good Luck to anybody who builds it.

    _________________
    Add a dab of lavender to milk, leave town with an orange and pretend your laughing at it.

    [ This Message was edited by: dasteph on 2005-04-21 14:53 ]
  • guesserguesser
    edited April 2005
    On 2005-04-21 14:52, dasteph wrote:
    I have tried to get an external version to work, but I've only had limited success, it all seems to come down to a problem with the csync signal provided at the Peritel connector.

    Just an Idea, and it's probably been sugested before, but couldn't your interface include some kind of booster/preamp, to bring the Peritel Csync signal up to a higher level for RGB?
    I don't actually know much about how Peritel/RGB work, as I have only so far ever used RF or Composite.

    I have trouble with RF interference from PSUs in my room, so I would be very interested in building this interface, but only as an external interface, as I only have one speccy, and I don't want to blow it up (again!)

    [ This Message was edited by: guesser on 2005-04-21 16:43 ]
    My rubbish website including the redrawn Amstrad schematics and the Sinclair Wiki.
  • dastephdasteph
    edited April 2005
    I've tried boosting the signal with an LM181, but after 5-10 min the signal starts getting wacky. Basically the colour starts to flicker black and white.

    Personally I wouldn't to be afraid to build an internal adapter. None of the signals used go back to the ULA or anything like that, so it would be pretty near impossible to kill your Spectrum, as long as you solder in the right places.
Sign In or Register to comment.