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Adding s-video to crt tvs


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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.20191110_145836.thumb.jpeg.b5cedfdc9619edbb695eee5481992ee4.jpeg

 

Sent from my SM-A520F using Aussie Arcade mobile app

Edited by jeffez
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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.

 

@jeffez can you post the model numbers?

 

 

 

 

lol, besides, @MarkOZLAD is the guru you want :)

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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-2170m3_2193m3_2184mt_2194mt-ch.gp-1a.pdf/download.html

 

https://elektrotanya.com/sony_gp-1a_kv-2965.pdf/download.html

 

https://www.alldatasheet.com/datasheet-pdf/pdf/115335/SONY/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.

Edited by buttersoft
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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.

Edited by jeffez
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I don’t have a lot of spare time to review schematics etc at the moment but from memory these cannot be RGB modded.

 

If I get a chance I’ll try and review S Video options.

 

On later sets you need to change service options to enable the S Video input, fill in the blanks on the chassis and ground a switch so the s video is detected.

 

It would be great if there is a variant of the chassis that has S Video implemented that could be copied.

 

 

Sent from my iPhone using Aussie Arcade

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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? @buttersoft

 

Sent from my SM-A520F using Aussie Arcade mobile app

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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.

 

410.jpg.15222fffa827e0aa1e3dfb8ae0375f2e.jpg

Edited by buttersoft
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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.

 

 

Sent from my SM-A520F using Aussie Arcade mobile app

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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? @buttersoft20191118_174354.thumb.jpeg.43d4627bc665a74d4236fa12b4d61529.jpeg

 

Sent from my SM-A520F using Aussie Arcade mobile app

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Hmmm, if the channel number is stable, and the rest of the picture is crazy, it'll probably be sync related. Or the distortion/stability part of your problem will.

 

Try playing around R302. Add a 1k pot before your Luma signal gets there. Then add it in series with R302 to ground, then same for R303. IF nothing works, put everything back to stock and..

 

Is it possible to input the Luma signal into the RF input and the Chroma signal directly to the jungle somehow? You might need to disconnect the Chroma coming from the RF input though...? Try Luma into the RF port, and then maybe into a few places along the video input line, like into pin3 of the YCM302, or pin 12 of IF201 (is that the tuner block?).

 

I should warn you that at the moment i'm pretty much guessing. I did notice that the missing pages from the jungle datasheet are added at the back, so you might be able to find more info there. It certainly says the chroma line is meant to be input at 2.5V, but whether that's offset or peak-to-peak i didn't look.

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Looking at the jungle datasheet for pin 46 y signal input pin is 6.4v and as you say 2.5v for input 1. I am now wondering if the C and Y coming into the jungle in link 2 schematic is not the same as what comes from the s video port. I noticed in link 2 diagram the C and Y lines connect out to a connector CNI1002 seen at the top of page 5 in link 2 diagram. It shows the physical s-video port (left hand side page 5) and all the circuitry between it and CNI1002, but i find it's really hard trying to follow the C and Y lines from the port to CNI1002. There's series capacitors and parallel resistors and transistors here and there...

 

I think you might be right with it being sync related because there's nothing to say the Luma pin on the jungle is listening for a sync signal.

 

With the R302 and R303 do you mean the voltage divider on diagram 2 resistors R301 and R302? It looks like R303 is the seperate 1k connected in parallel between the emitter on pin 46 of the jungle.

Just want to make sure as it'll mean ill have to dismantle the tv again and cut and reroute another pcb trace.

 

I should make sure you know what i have done. So far i have cut two traces. One at the base of Q301 that feeds into pin 46 and the other at pin 1 of the jungle. This way I can completely replace the C and Y lines with are supposed to come from YCM302. I am able to successfully run it in back in stock rf mode by just running my own wires from YCM302 through a breadboard then back into tv where i cut the 2 traces. So the picture i posted above has no connection to YCM302, it's just C and Y from the s-video port with a 1k resistor to ground on Y going into Q301 and jungle pin 1. After seeing all the complex circuitry on page 5 of link 2 i am fairly sure this is not right and i should have a least a series capacitor of some sort...

 

Is the video signal coming into YCM302 pin 3 effectively a composite signal? Your saying connect luma there and keep the Y connection between YMC301 pin 5 and Q301 but disconnect and pin 1 and run C from the s-video port? I know we are both guessing at this stage, i just want to make sure i follow. I plan to post a final working schematic if i get this working!

@buttersoft

 

Edit - I managed to trace the circuit for just pin C of the S-Video port (link 2 page 5) to the Jungle pin (link 2 page 4).

[s Video Port - C] --> 0.01f --> 0.01f --> 0.01f --> transistor (12v) --> 0.01f --> Jungle Pin 1

I am having trouble tracing what's going on with the S line though, it looks more complex. Maybe i could replicate this circuit? Looks both C and S are being amplified with a transistor before reaching the jungle chip.

Edited by jeffez
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Yes, internally it's probably going to be very similar. At least my brain tells me so? I think that schematic you describe is mostly a series of switches to determine which input is used.

 

At this point you'll just have to start trying stuff. I'm happy to keep trying to advise, but it's not going to be very reliable or knowledgeable advice, i'm afraid.

 

TL;DR we have gone well past the point where an RGB mod on an entirely different, free consumer CRT would have been much less hassle :)

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Thanks matey you have been a great help! Yes this has probably gone beyond what was hopefully going to be a simple mod. Especially if my posts have got too long to read! :lol

If these weren't small trinitrons i probably wouldn't go to this much effort. I'll keep on trying and maybe ask around other places. If i get it working ill post a schematic here. Cheers

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not sure if that would be of any help but I did a svideo mod/restore to a Sony before:

 

Awesome thanks. Incidentally i got it working just last night and plan to post schematic once i have done some more work and testing. I might try the chroma circuit you did just to see if there is any difference. As it happens I have the 25" version of the higher end model you mentioned in the video with the component inputs.

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Here is some diagrams on how it works. There is also this thread which goes into more detail.

As buttersoft mentioned the luma is connected to the video line coming from the tuner block to provide sync. The other thing i needed to do was add a termination resistor and series capacitor on chroma.

 

[ATTACH=CONFIG]156836[/ATTACH]

 

[ATTACH=CONFIG]156837[/ATTACH]

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