Adding RGB inputs to TV, how hard would it be?

[Jack Burton]

Topic for discussion.

As we see the decline of the CRT arcade enthusiasts will need to turn to alternatives to achieve an authentic arcade experience.
 
We are already seeing this with many people using televisions in their cabs in one forum or another in place of an arcade monitor. 

Others take this one step further and perform a tube swap with an arcade monitor to create a device that is close to a new arcade monitor.

In Europe gamers are lucky because they have televisions that accept RGB connections over SCART.

In the US gamers quest after high quality RGB studio monitors.


So, how hard would it be to take apart an NTSC television and add RGB inputs to it?  I know that every TV uses RGB at some level, if only to feed the scanning electron guns used to create the image on the CRT. 

Can the signal to these guns be intercepted somewhere on the television chassis, and we can supply our own signal?

[MonMotha]

In many cases, there is a set of coaxial cables (or, on cheap TVs, just a ribbon cable) running from the main tuner/deflection board up to the neckboard that'll have RGB video on it since the NTSC demod is often done in with the tuner stuff.  Sometimes, this video is YPbPr ("component"), though, and the colorspace is changed on the neckboard.  Depends on the TV.  Signal levels are not always standard, of course, but sometimes they are.

If you can determine the nature of this interface, yes, you can chuck RGB video onto it.  You still need to feed sync to the deflection generation circuitry in a meaningful way.
If you have sync-on-green, you can just hook that green channel up to the composite video input and then splice the three video channels right up into the neckboard in a manner that is suitable (may need an amp, for example), and it should work (OSD may be weird).
If you have TTL level sync, you'll have to either create SoG or figure out if something simpler will work as an input to the deflection generation (may even be able to find a TTL input somewhere).  May need a sync separator if you just have composite sync and of course polarity inversion may also be required.

This is not going to be the type of thing that's guaranteed to work on every television, but it is often possible.  The technique will also only work on analog televisions.  Anything with a digital scaler will probably want to buffer the video digitally, and that will get all the timing out of whack.

Many newer TVs in the USA have YPbPr component inputs.  It's not too hard to convert RGB to YPbPR; it's just a colorspace change.  4 high-speed op-amps and a handfull of passives is sufficient plus some extra stuff to handle sync insertion on luma, or it can be done digitally. This has the advantage that you don't have to mod the TV.  Boxes can be bought that do this for about $75.  S-Video is also an option.  It looks surprisingly good on many TVs when done right.  The crappy S-Video outputs on PC video cards don't do the format justice.

[Hornpipe2]

How funny!  I was just looking up information on the same thing - hoping to upgrade the weak composite hookup on my cab to a full-fledged RGB.

Here's a topic on the subject from 2004: http://forum.arcadecontrols.com/index.php?topic=21565.0
Here's a link to some people who have successfully done it: http://porkrind.org/arcade/tv-hack.html

I suspect it's not really that hard, if you can find the signals... which from what I understand are on one of the sets of wires running from the TV main board to the one on the back of the tube neck.  You still need a way to bring in sync, too, and I guess you need a 15khz tool to run your games at the right rate or you may damage the TV...?

ETA:  In some cases, if you've got an existing composite cable, you can leave it attached and it will continue to provide sync while you actually feed the RGB straight to the guns.

[Jack Burton]

about S-video:

It can look 99% as good as component in the right situation in my experience.  Some console releases of arcade games run in native resolutions, and when connected over S-video the image is almost indistinguishable from an RGB arcade monitor running the same game.

I have run Twin Cobra and Dodonpachi tonight on my Toshiba 36A60 and it just looks really really good.

about RGB:

It appears that there is not going to be a way to create a universal tutorial to do this mod.  However, what televisions would be good to look out for?  

I have an RCA Lyceum TV.  I bet it could be done with it.

How would contrast and brightness adjustment be achieved in this mod?  Will it work the same as always, or do you need to do something with the signal?

This discussion was really a purely theoretical thought I had.  If the mod were particularly easy, such as soldering onto unused pins on the chassis, then that would be very productive.  

Do you think that might even be the case sometimes?  

For practical purposes things like sync converters and colorspace converters do a very good job, and if I were to use a tv in a cabinet I would probably play around with one of these first.