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B&W output only - not sure which pins to use

rja4096rja4096
edited August 2008 in Hardware
Hi, Looks like my PSOne LCD screen needs a composite and not an RF signal, so I'm trying inputting from the RGB to get a composite signal (rather than do the rf to composite hack on the modulator).

I've tried every combination of the pins, I thought pin 1 (composite) and pin 4 (composite sync) would work. All I can get is pin2 GND and any one of the RGB pins (6,7 or 8). Which actually works, but onlt black and white.

Please Please can someone tell me what I'm doing wrong.

This is on grey +2

Thanks, Rick
Post edited by rja4096 on

Comments

  • PhuPhu
    edited August 2008
    Going by this pinout:

    http://pinouts.ru/Video/ZxSpectrum128Rgb_pinout.shtml

    Pin 1 as signal and pin 2 as ground should work fine.

    If not, you may need to tie pin 1 to pin 4 (not sure if the Speccy's CVBS out includes the sync signals).

    If this doesn't work I'd suggest a fault with either the circuit board, or more likely the TEA2000 encoder video.

    The B/W signal you're getting isn't a real B/W signal. Pins 6 7 and 8 are R G and B respectively. And only indicate if a pixel has that particular component. If you use the R line for example, blue and green will appear black.

    There are simple circuits that exist to do a simple RGB+Sync -> B/W video conversion, but I suspect you'd rather have colour. If you can't get composite video to work, there are RGB to Composite convertors but they tend to be pricey.

    Sadly, TEA2000 is the one chip I don't have spares of, and these days they are rarer than rocking horse defecations.

    -- Richard
  • rja4096rja4096
    edited August 2008
    Yippee, This works, pins 1 (composite) & 4 (composite sync) together with pin 2 (ground).

    The display is very poor, I might get another Speccy from Ebay to see if any better - think this one is a bit knackered.

    - Or could it be that I''m not using any shielding.

    Thanks, rick
  • guesserguesser
    edited August 2008
    rja4096 wrote: »
    Yippee, This works, pins 1 (composite) & 4 (composite sync) together with pin 2 (ground).

    The display is very poor, I might get another Speccy from Ebay to see if any better - think this one is a bit knackered.

    - Or could it be that I''m not using any shielding.

    Thanks, rick

    I think it's more that the signals available on that socket are weak and noisy anyway, that's what I read anyway.

    For composite, you really are best taking the signal off the modulator input (and building the little matching amp)
    My rubbish website including the redrawn Amstrad schematics and the Sinclair Wiki.
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