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Adding a RGB input on TVs

Started by Gradius, November 29, 2005, 03:25:50 pm

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Gradius

November 29, 2005, 03:25:50 pm Last Edit: November 29, 2005, 03:27:18 pm by Gradius
Hi Folks,

I want to add RGB input to my old TV, its a Sony Triniton 27" from 1998.  My TV have just video compose (RCA) and S-Video (Y/C) inputs.

Where can I found diagrams for this?   Don't need to be exactly the same to my TV model, I'm just looking for some references and infos.

Thanks,
Gradius

mr. newbie

well somebody kinda brought up the same thing in this thread
http://nfg.2y.net/forum/index.php?showtopic=1718. it seems pretty dangerous and fairly complicated.  

viletim

That's especialy true with Sony sets. They make their own jungle ICs, no chance of an RGB input.

dustinh2k

I have added an RGB input to my Toshiba MD13M1 13" TV/DVD Combo.  It was really not that hard.  I traced the RGB signals in reverse from the picture tube until I arrived at the video decoder chip which converts all the composite/s-video/etc. inputs to analog RGB output.

I spliced into these lines, adding a switch to retain original functionality.  Basically you are hijacking the internal RGB signals and replacing them with your own, in my case from a PS2.  I had to pull up the RGB lines from the PS2 with 5V (available on PS2 multi-out) and some resistors, experimentation was required to find a suitable pullup value to get acceptable brightness.  I used a pot to make the brightness adjustable.

For sync I kinda cheated but it works great.  I simply connected the composite video signal from the PS2 to the composite input on the TV, and let the onboard decoder chip do its thing like usual.

Operation is pretty simple.  In the off position, the TV functions like normal.  When I want to use the RGB input, I set the TV to the composite input, flip my switch, turn on the PS2 (set component output to RGB in the settings screen), and we have beautiful RGB.  The only drawback is there is no on-screen display, and the brightness/contrast/etc. controls on the TV have no function.  This is because I tap in after all of these adjustments are made.

I believe this can be done to any somewhat modern TV using this method, but you will have to do your homework.  Finding a datasheet for your TV's video decoder chip is very helpful.  

If anyone is interested I could take pictures or provide more info.

viletim!

dustinh2k,
If I was to modify a TV like that I'd expect to see video distortion whenever there's a picture with lots of white in it. The white will look a lot brighter than it should. Is this the case?

dustinh2k

viletim!,

No there is no distortion or extra whiteness.  I'm curious why you expect that?

viletim!

ah, nevermind... dunno what I was thinking...

btw you'll have problems with such a setup if you connect something different to the input (you'll have to re-adjust everything), esp anything with AC coupled video (that is any video with a capacitor somewhere in the signal path).

though as long as it works...

dustinh2k

Yeah for now I am only using it for the PS2 and it does work pretty good.  About the only thing I have noticed is a slight purple tinge if I have the brightness up too high.  I have been meaning to mod my N64 for RGB and try it on there one of these days, but I agree that everything will probably need to be re-adjusted.

This was more of a prototype that looked so promising I had to solder it onto a pcb and make semi-permanent, and it worked so well I never bothered trying to improve it.  However I would like to make it more universal, so that I could just plug in any console and not have to recalibrate everything.  If you have any suggestions for signal conditioning, etc. it would be much appreciated.

Sure wish I had access to an oscilloscope, this would be much easier!

Guest

The main issue is DC restoration for those AC coupled signals, which shouldn't be a too complex circuit.I also had perfect results with PS1/PS2 signals when trying this but lots of issues with signals from the XBox or Dreamcast.Be careful too, not just for safety's sake as it easy to render a TV useless if you stuff the composite video input or any of the RGB lines.One more reliable option other than buying a RGB monitor, is to  get a chassis from www.8liners.com and swap it into your TV.Its not perfect either since some TV tubes do not work well with the 8liners chassis's (pincusion issues usually) and you lose the abililty to watch normal TV, but at least you can control the screen positioning somewhat and you are guaranteed to get something universally working without a lot of technical knowledge and trial and error.

viletim!

My AC Coupled Video Amplifier might do the trick. Hot off the drawing board.

There's a bit more gain than required but it's easily adjusted - or just add a resistor potiential deviders on the outputs. If you can find a sandcastle pulse in the TV guts somewhere you can do away with the LM1881. Not very likely with the level of integration of a modern TV though... I suppose you could just clamp off a sync pulse though that would get you into trouble if there's any sync on the video signals (and I hear there's some on the PS2's video output). If you want to get really crude, just clamp off a flyback pulse.

ido8bit

Find the datasheet for the jungle IC in your TV.  While this is probably impossible for the Sony many other TVs use Sanyo jungle ICs which DO have RGB inputs as they are designed so the same chassis  can be used in sets for sale in the European market.  

Datasheets can be found on eletroka.pl, datasheetarchive and others (though some of the others do require hefty membership fees).  

dustinh2k

I finally have an update on my project, and its very good news!

I have a datasheet for my TV's jungle IC but it is in japanese...  I got ambitious and used google to translate sections and discovered external RGB input pins with input level 0.7 Vp-p/100 IRE and an enable pin.  This happens to be how the TV's on screen display is piped in, by rapidly switching the enable pin whenever text needs to be displayed.  So, I just connected my 4 pole dual throw switch in a way that intercepts the RGB and enable lines, replacing them with my RGB signals and tieing the enable high.

At first the image was overly saturated and way too bright, but then I realized I forgot to terminate my RGB signals...  A few 75 ohm resistors later and everything looked good.  Still no on screen display while in RGB mode, but I can easily switch back and forth if I need to make adjustments.  I also found a way to adjust RGB settings in the service menu.

I still use the composite video input for sync.  I made a PS2 A/V cable with composite video, audio, and a standard HD-15 VGA connector, and added a VGA cable to the TV.  This makes it easy to connect my 19" Dell Trinitron for games that support 480P (it supports sync on green).

This seems to be the best solution for this TV, and works much better than my first attempt.  Next step: mod my gamecube component cable with an RGB/YPbPr switch and add a VGA connector!

Does anyone else spend more time hacking their consoles than playing them?

viletim!

dustinh2k,
A lot of the shitty turkish/chinese sets use an analog .7Vpp 75 ohm RGB input for the OSD. These sets quite often share a the single RGB input on the jungle IC between the micro (for OSD), the teletext and the SCART RGB input, kind of like an 'video bus'. On these sets it's totaly normal for there to be no OSD when using the SCART RGB input.

However, most TV sets in general have a digital RGB input on the jungle IC dedicated to the OSD (no need for more than 8 colours anyway). This doesn't mean there's not going to be another, analog, RGB input elsewhere on the IC. In the absence of a circuit and data sheet, you can identify an unused analog RGB input by looking for three pins next to each other with 0.1u decoupling caps (usualy ceramics) hanging off them. The RGB enable line (usualy a TTL type input) will likely be on one end of the three video inputs and will be connected to ground.

Most of these analog inputs like a 75 termination resistor and a 0.1u series cap. Some older TVs want 1u (bipolar electro usualy) series caps.

btw. The original idea behind putting an RGB input into TVs was that at the time (early 80s) they believed that future consumer A/V devices would use RGB for the OSD/menus and composite video for the picture content and have the TV combine the two. That's why the rgb status/fast blanking input is a 75 ohm thing like the video and not something like TTL or the other (12v) status line.
QuoteDoes anyone else spend more time hacking their consoles than playing them?

Playing them... now there's an idea!

dustinh2k

I was going to say I wish you would have mentioned the OSD thing earlier, but it was quite exciting to discover all of this myself while poking around with the multimeter.

Interesting backstory on the RGB inputs...  Makes me wonder why the manufacturers were (are?) so afraid of using RGB connections for video instead of composite/s-video/etc.

viletim!

dustinh2k,
You're done really well if all you're using is a multimeter!

I think the reason for the lack of RGB sockets outside of europe in the past is simply because joe public didn't have any use for them. But there's no excuse, with the advent of DVD and video games becoming very popular, for ignoring this well established SCART standard and shitting out this inferior 'component video' thing.

At leas most TV jungle IC makers are on our side :)