Hacking televisions - Rgb??

[Born A Trumpet]

Down here in Australia we have no SCART, no RGB, and s-video is only just being introduced.
I'm wondering if there's a mod to add RPG inputs to a conventional composite/RF television?
If rgb is the native signal of all televisions (the three cathode guns), surely there is a way to by-pass any converters or decoders?
The scan rate (a crappy 50-60 hz) is right for consoles, is it not?
So why aren't people doing it??

[NFG]

This has been covered before.  

The reason no one does it is 'cause of the ludicrously terrifying voltages present inside a TV, and the fact that no two are alike.  It's a bad idea.

[Born A Trumpet]

Fair point. . . .

However have you thought about paying a repairman to do it?
I'm sure if you went to the local repair shop there'd be a technician willing and able to do it for a reasonable price.  
Do they even have repair shops outside of Australia? <_<
They're getting harder and harder to find. . .
Everyone would rather have a new tv than get their old one fixed  

Thanx for an answer anyway

[NFG]

I've found that TV repairmen are a bunch of frauds who know only how to follow a schematic and want so much for their time (something I can identify with, actually) that repairing a TV costs more than replacing it.  Ditto for asking them to mod it, especially if you want a nice socket and RGB levels adjusted for proper viewing.  You can buy and ship a 14-inch RGB monitor, often capable of 15+31kHz, for less than a hundred US dollars, why pay more for a half-assed job on your lovely TV?

[Zaarin]

Well, it IS possible. RGB is one of the few signals that doesn't get changed inside the TV. What you need to find is the RGB amplifier, sometimes it's an integrated one (one big chip) and sometimes it consists of discrete components. If you solder a connector to the inputs of the amp and then connect that to a console, you should be able to send RGB signals directly into the tube. You also need to input the composite out from the console for sync.
The only problem I can see is removing the picture information from the composite, because this mod will simply add the RGB signal to whatever the TV already sends into the RGB amp.

To do this successfully you probably need the datasheet for the RGB amplifier, and also the schematics for the TV if the circuits aren't marked (or if you don't feel like measuring the circuits with a multimeter for a few hours.

By the way, if you try this out, I'm not responsible  

[Chuplayer]

The reason no one does it is 'cause of the ludicrously terrifying voltages present inside a TV

I was actually going to take apart this crappy TV in my parents' basement just for the hell of it, but they threw it out before I got to it. I was mad at them, but now I guess they did me a favor. Still, I wonder what the "ludicrously terrifying voltages" would've felt like  

I also wondered why nobody cared to hack up a TV and make custom RGB, but now I know why.

[Zaarin]

Well, the only ludicrous high voltage is the one going from the line transformator into the tube. It's a thick, insulated wire with a HUGE plug. You have to be really stupid to get a shock from it
The other semi-high voltages are the amplified RGB signals going into the TV (300-450V), but who touches the circuit board while the TV is plugged in?

[gannon]

Yeah, but I opened up one of my 13" tvs once and it had around 15 huge capacitors all along the board. So unless you actually discharge them they can be very dangerous!

[benzaldehyde]

Yes, those power caps are where the real danger is. They can hold a charge for days and still give you a horrifying shock. It just isn't safe to muck around inside a TV/monitor unless you have a good sense of what everything does.

[Zaarin]

Or you can wear plastic gloves
I've touched capacitors that doesn't discharge into the circuit it's connected to. The current leaves small, white rings on your fingers where your touch it, hehe.

[Darklegion]

Just disharge the caps when you it up...danger gone.Most tvs do that for you anyway if they are not ancient tvs,or arcade monitors for that matter.Its simple to test each time in any case with a high voltage tester...just one of the cheapo lamp ones will do,they will glow when any voltage is present...even without contact although that method is not so reliable.As for the hack itself...it can be very easy or a real pain in the arse depending on the tv and the method you use.I have done 2 tv's in the past,1 was just a standard scart tv without the scart connector so it was very trivial to solder a connector on.....that of course was pure luck,but there is a small chance that you will find something like this on an Australian tv since they are often just built using the same chassis that is used in europe,which tends to use scart for the most part.
The second method I used was to run the rgb signals into the main TV chip which could handle scart signal...this time a chip designed for europe but with less circuitry this time.I had to wire in the fast blanking pin to force it into rgb mode....perhaps I could have even got it to auto-switch to the AV channel,or tried to get it to work manually with a remote,but was not really needed.
Lastly I found a TV that would just not work with external rgb signals properly through the TV chip.SO i tried inserting it at the output stages of the tv chip...the ones that go to the neckboard then are amplified to around a 40V down to 0V I believe...also as a side note I think that the rgb signals are inverted at this stage and have read information confirming that...have also seen it happen myself,as when you ground a particular rgb wire it flares up to full brightness.But thats not really important to this.
Anyway since I  was skipping the pre-amplifier stage,it was too dim for the tv neckboard amps to accept,besides the psx which worked almost perfectly and to a lesser extent the saturn which was too dim but visible...the rest of my console were not visible at all.
I tried 2 different amps and made certain modifications to each of them.1 was one designed for arcade monitors and made by ultimarc.It worked okay for VGA output and for my xbox,but had issues with DC restoration which resulted in a lack of details in black areas...which made playing games like resident evil style games impossible and made the rest look inaccurate.And the dreamcast would flare up on the opening white screens which suggest the same effect.Then I tried the CXA series of sony chips ,which didn't amplify to a level I was happy with and lacked the flexibility that I needed.
I am now going to try a very simple method involving transistors suggested in the arcade controls forums...just need to find some time so I can work on it.

[NFG]

This is exactly the problem - even if you're told to discharge the caps you need to know that not all tubes require this.  If you don't get a massive SNAP during discharge how do you know if you'd done it wrong or if it didn't need doing?  And don't forget you need to do it twice, with 10-20 minutes between 'em, to get the whole charge.  And then if you're clumsy you'll STILL get a nasty jolt, as my friend will attest.

And then you get these other problems - incompatibilities, contrast issues, sync problems, etc etc ad nauseum.  This is exactly why it's a stupid idea.  Buy a monitor, save the hassle.

[Aidan]

Throw in to that mix the fact that some TVs operate their chassis ground at wierd potentials; it starts to look too much hassle unless you know what you're doing!  

[DarthCloud]

I did it today on my NTSC tv. And it work fine with my SNES and N64 but the picture is dark ans very dark on my n64.

If you want to do it first find the service manual or the schematic of your tv and find the rgb in and the pin switching on the rgb encoder chip.

Personnaly I think that was not a stupid mod but yes it's degerous. But with my tv I can access to the rgb encoder chip just by get a part the back panel of my tv without touching the pcb and I have just to solder my four wire. In this way it's not dengerous.

I made a switch in the side of the tv for swiching to rgb and I make my rbg connector like the componant video are with 3 rca jack. I plug my rgb wire + the CV, i put swith on and voila!!

If you want do it go here they have a lot of tv sch�matic and service manual!

http://www.eserviceinfo.com/

And for my dark picture probleme i think it's because I don't have the capasitor that are in the normal Scart cable. Maybe I will add them to the back of the RCA jack.

Exuse my english I'm front Qu�bec!! (Canada)

[Martin]

I was wondering, how long does it take for a TV to discharge itself anyway?
I have a PC monitor, It's been lying unplugged in my atic for 7 weeks, Is it safe to open up? Or do I need to leave the power switch in the ON position for it to discharge?

[NFG]

Sometimes a monitor can hold a charge for months, and why not?  It's not being used, the charge just sits without an outlet.  Many modern monitors (arcade + consumer) auto-discharge, but some don't.  You'll never know which you've got until you try and discharge it, either with the proper tools or with your finger (ouch!).

[Darklegion]

As i said get a $5 high voltage checker and you will always know immediatly.Alternatively build your own disharger/tester with a high wattage 110V/240 V light bulb and wire it some test leads or some screw drivers even if you don't have any test leads.You are correct though,it is risky to do this but certainly worth the risk despite the problems you may come accross.Personally I cannot stand using a rgb monitor simply because of the size..they are just too small....I'd personally use a large composite tv over a commodore monitor,the tv needs to be a certain size or I can't be drawn into the game/movie deep enough.Nonetheless composite doesn't cut it for me,and that is why I do this.And up till the most recent one I have had very good success...just need to sort the problems I'm having out and I should be able to do it on any tv and with all I have learned recently I'l  be able to figure out alternatives quite easily if I run into another 'problem' tv.

[Endymion]

You know there are large RGB monitors out there right? If you can't find one readily outside of ebay or that isn't used just call an arcade distributor. They've got plenty of big ol' honkin' monitors. I think pulling apart a TV is going to be even more niche than using an RGB monitor.

[Darklegion]

I think pulling apart a TV is going to be even more niche than using an RGB monitor.

Yep,you are spot on......and that is the fun of it  
Arcade monitors are too expensive here,90% of the time you'll have to buy the whole cabinet to get hold of one.The 8liners chassis is another alternative but picture quality is often not perfect,depending on the tv......I believe that perfect quality and full control is possible with only cheap parts and a basic circuit.Figuring it out is the hard part...and also the fun part

[Segasonicfan]

Hey does anyone have any idea what the RGB decoder chip might look like?  I'm going to try to find one on a pocket TV which means much less searching  Of course, I can't find the schematic for either of my pocket TV's so I'm gonna have to find it myself.  Does anyone have any idea of the voltage that would run through a chip like that?  Maybe I can find it with y multimeter.  Also, if there's any ideas on how many pins it would have that would be helpful.  There's gotta be some sort of standard to that chip...

-Segasonicfan