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Adding s-video to crt tvs

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  • Adding s-video to crt tvs

    Hi everyone,
    I'm wanting to see if there's anyone who can point me in the right direction with adding composite and s-video to old crts. I've got a couple of sony trinitrons which have great picture but only have rf on one and rf and composite inputs on the other. They could really do with s-video to get the most out of them.Click image for larger version

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    Last edited by jeffez; 11th November 2019, 07:43 PM.

  • #2
    You'd be better off adding RGB. Paging [MENTION=16024]buttersoft[/MENTION]

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    • #3
      RGB is normally just as easy, and a better option. But in a lot of cases you'd be able to add S-video too, if the pins are present on the jungle. I say that without having attempted it, however.

      That vintage might be tricky either way, though. If those models don't have an On-Screen-Display, and no SCART sockets or partial evidence thereof, they probably don't have RGB inputs on the jungle. One way to tell is if they have a little red 8-segment LED showing the channel and it's not shown on the tube. I had a crack at a Sony like that and didn't get very far.

      [MENTION=8231]jeffez[/MENTION] can you post the model numbers?




      lol, besides, [MENTION=10567]MarkOZLAD[/MENTION] is the guru you want

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      • #4
        Yeah they are a bit older and so i wonder if doing any kind of rgb/s-video is even realistic. The channel numbers are displayed on the screen.

        Smaller one is KV1414AS and has rf input only

        Larger one is KV2184AS and has composite (mono) and rf inputs.

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        • #5
          I cannot find the service manual for either of those sets, but google indicates the larger set uses the GP-1A chassis, and I can find a service manual for some models that are likely very similar.

          https://elektrotanya.com/sony_kv-217.../download.html

          https://elektrotanya.com/sony_gp-1a_.../download.html

          https://www.alldatasheet.com/datashe...CXA1213AS.html

          So, it looks like the micom in these (IC002 / PCA84C64OP or 840P) muxes a single Green output into the Green output of the jungle chip (IC301 / CXA-1213S). Added to which, the closest datasheet i can find for that jungle is missing pages. I don't think that jungle chip has RGB inputs. It does, however, have S-Video inputs as a Y/C jungle. If you look at the first service manual i linked to, page 17 of the PDF, reference D/20 shows an IC labelled YCM301 (YCM103?) for which i can find no information. Coming from this are the Y and C lines which go into pins 46 and 1 of the jungle respectively, the former through Q301 and a divider. I'm not actually sure if a Y/C jungle takes Y/C directly, or in some modified form.

          So, it looks like there's a configuration for S-video that you might try, assuming your set matches the configuration in the top service manual. If it does, you could basically modify it to be like the second set of schematics. I would inject Y into the base of Q301, adding a 4.7k resistor to the 9V line and a 2.2k resistor to ground for a divider network. I would also look at removing R302 and the connection to pin 5 of the YCM301 that feeds to Q301. Chroma can be fed directly into pin 1 of the jungle. (You might also try it without the divider network first, and without removing R302).

          Blech, i hope this steers you in the right direction, but i can make no promise it will work. If it doesn't, you'll need to go through the schematics and compare them to the set in more detail. Do the PAL/NTSC and BW/colour siwtches matter? Is the Y line enough to feed Sync into the jungle or does it need a sync input somewhere else? I can't answer these directly.

          It's also possible that jungle has RGB inputs, pins 34, 35, 36 with pin 33 for blanking, but i think pin 32 (sync) is actually a sync output and you'd need to again feed sync into the Y line as per above. And i can't find any SCART sets using this jungle, and the inputs are only shown using SECAM.
          Last edited by buttersoft; 11th November 2019, 10:26 AM.

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          • #6
            Thanks for looking that up. I think i will need to open one up and look for the jungle and other chips to see what Manuel matches. I haven't worked on crts so i best make sure i know what i am doing with discharging the flyback before poking about.

            The YCM301 does infact look to be providing s-vidoe lines to the jungle chip. I'm happy with s-video if that's the best (easiest?) approach for now. It's allot more common and easy to get s-video cables for old games consoles and the difference between that and composite is massive. Would like to add composite as well to the smaller set which only has an antenna input. Haven't even considered audio just yet.

            You could be onto something with pins 33 to 36 for rgb and yeah 32 looks like it's output as it connects to the base of another transistor Q003. I'm a bit unclear on how its being used but this is where the traces seem lead to ignoring the series capacitors.

            33 > Q003 (base)
            34 > GND
            35 > R - Y
            36 > B - Y

            I'll most likely just do the s-video anyway then later on maybe try out the rgb when i have a better clue on what i am doing.
            Last edited by jeffez; 11th November 2019, 01:03 PM.

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            • #7

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              • #8
                Originally posted by MarkOZLAD View Post
                It would be great if there is a variant of the chassis that has S Video implemented that could be copied.
                That would be the second schematic listed above

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                • #9

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                  • #10
                    I opened up the smaller tv and it does infact look to have the CXA-1213S and a YCM302 next to it.Click image for larger version

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                    • #11
                      I managed to dismantle it and now want to put it back together but the fat flyback wire from the coil to the tube is stubborn and I can't disconnect it at either end. So the tube is teatherd to the pcb. Is there a trick to this, or are some tubes permanently attached to the flyback? [MENTION=16024]buttersoft[/MENTION]

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                      • #12
                        The lead will disconnect from the anode button, but never from the flyback. The shatter hook at the end, under the anode cap (rubber suction-cup looking thingumy) comes in a couple of versions, but essentially it's an upside-down "U" shape with barbs sticking outwards from the tips, and you pinch the tips together to release it. This can be done a few ways, but if you've never done it before - WARNING ** DISCHARGE THE TUBE FIRST - then peel back the cap and take a look. Once you can see one of the metal uprights of the U, slide the flat blade of a screwdriver under the rubber cap, being very careful not to snag it, and push the metal inwards until it can lift free.


                        Note: do not remove the solder lock, this pic is just to show the vague shape of what you're working with. And it might not be flat but could be a single, thick stiff wire. The concept is the same.

                        Click image for larger version

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                        Last edited by buttersoft; 16th November 2019, 05:56 PM.

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                        • #13
                          That worked thanks. Couldn't seem to find a answer with Google. I'll be testing out the s-video circuit tomorrow. After probing the pcb I found it's the same as the first schematic linked except it's a 1k not 1.5k used.

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                          • #14
                            Ok so I have tried with the 4.7k and 2.2k voltage divider and removed the R302 (1K) resistor and it shows up just as a black screen with just the green channel number overlayed. The normal old rf still works if I change it back to the original circuit meaning I at least haven't broken anything. I have both configurations on a breadboard with 6 shielded wires running into the tv so I can easily change things around.


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                            • #15
                              As suggested alternatively i tried without the voltage divider and kept R302 resistor. Basicalky just swaped lines coming from the YCM302 and I finally got something. But it's still not there. The picture is black and white and all messed up and the v position drifts slowly downwards. You can faintly make out the donkey Kong title screen as I am testing with a snes.
                              Does this look familiar and is there anything else I could be doing? [MENTION=16024]buttersoft[/MENTION]Click image for larger version

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