Hacking a TV for composite

[SirPeale]

I found a TV on the road today, some POS Symphonic.

It has coax input only.  But it has this chip:

http://pdf1.alldatasheet.com/datasheet-pdf/view/920/MITSUBISHI/M52339.html

I figure I can piggyback the input circuits to get a picture.  I'm looking to hack in a composite interface.  Thought I'd hack in a Jakks game (or anything else that requires composite output).

Suggestions?

[qrz]

the IC has the capability of accepting direct a/v inputs.
u will need to construct the appropriate input/switching circuitry ....

the main concern would be the type power supply . if a linear regulator , an isolation xformer will be needed .
either on the AC or a/v input circuits...

a smps "should" provide enough isolation to not be a problem.....

that said , the big question is WHY was the set tossed ?   DOA , intermit ...

73 y gud luck de qrz

[SirPeale]

that said , the big question is WHY was the set tossed ?   DOA , intermit ...

It works fine.  It was on the curb.  Around here, when you want to get rid of something, but don't want to actually throw it away it goes on the curb.  Someone will usually pick it up.

Likely someone got a new TV and didn't want this one.

[Level42]

If you're going to hack, why not RGB ?

[SirPeale]

Because I'm not going to use this for arcade stuff, I want to use it for a Jakks game.

[qrz]

"It works fine.  It was on the curb.  Around here, when you want to get rid of something, but don't want to actually throw it away it goes on the curb.  Someone will usually pick it up."

good find .. the price is right   

been selling crts like that ( as used - of course !) to a local route operator .
he gets his games up and running cheap , and i make a couple of bucks in the process ... win- win 

qrz

[Level42]

Because I'm not going to use this for arcade stuff, I want to use it for a Jakks game.

Figures

[richms]

I couldnt see anything in that pdf about how to make it switch over to the video in pin rather then the tuner it is controlling.

[SirPeale]

That PDF is just the pinout for the chip.

I have no clue how to get it to switch things over.

Is it possible to tap into the tuner pinouts instead?

[richms]

Possibly, it looks like it has an output from the tuner and then an input back into it, but no idea what level shifting you will need to do to get it looking even half decent.

Realistically, buy a modulator and be done with it, limited resolution shouldnt be a problem with the source, and they are usually not to bad noise-wise when you dont try to have the antenna signal mixed in with it as well.

[SirPeale]

Realistically, buy a modulator and be done with it, limited resolution shouldnt be a problem with the source, and they are usually not to bad noise-wise when you dont try to have the antenna signal mixed in with it as well.

I have a modulator already; but what's the fun in that?

You call yourself a hacker, boy?!?!? 

[richms]

I am someone that realizes that hacking something because you can isnt a good enough reason to do it when there are cheap solutions that let you move onto the more fun parts of the process like building the cab

[SirPeale]

I've got eight cabs already.  The fun is in the hacking.

Moving right along...

Would a photo of the PCB help?

[Level42]

Schematics would be better. I remember that I had a small B/W TV that was hacked for composite video to use as monitor on my Atari 600XL, so it is possible. I didn't do the hack myself then however.....

[ChadTower]

Compromise hack:

Yank the modulator off of a VCR and use that.

[Level42]

You get a terrible picture with a modulator.

Composite->modulate->demodulate->composite video. A waste really.

If you can find (in the schematics) where the TV signal has been de-modulated, that should be the point to insert your signal. In theory.....

[SirPeale]

The input would be that chip, wouldn't it?

[Level42]

The tuner is connected to that chip, so yes it does the decoding. However, since there is also RGB outs on it, I fear that there might be no composite video signal (there is no use for it in a TV set if you already have RGB).

It might be pin 51 though (video out).

[richms]

You get a terrible picture with a modulator.

Composite->modulate->demodulate->composite video. A waste really.

If you can find (in the schematics) where the TV signal has been de-modulated, that should be the point to insert your signal. In theory.....

There may be a way on that chip since it looks to loop the tuner out back into it on the schematic.

A modualtor will give more resolution then an arcade machine has - ntsc is already messing the image up something major the added RF stage will do nothing to it. Modulators are only noisy when you have them mixing into an already polluted RF spectrum, and since  the TV will not be used for TV it can just be left on CH36 or whatever the modulator is set to and the input to the modulator can be shorted out to stop it picking up noise off air and amplifying it.

[SirPeale]

Hm...I'm thinking I could hack RGB into this as well.  It's got the points on the chip where it comes out, should just be a matter of splicing into that, right?

[Level42]

You get a terrible picture with a modulator.

Composite->modulate->demodulate->composite video. A waste really.

If you can find (in the schematics) where the TV signal has been de-modulated, that should be the point to insert your signal. In theory.....

There may be a way on that chip since it looks to loop the tuner out back into it on the schematic.

A modualtor will give more resolution then an arcade machine has - ntsc is already messing the image up something major the added RF stage will do nothing to it. Modulators are only noisy when you have them mixing into an already polluted RF spectrum, and since  the TV will not be used for TV it can just be left on CH36 or whatever the modulator is set to and the input to the modulator can be shorted out to stop it picking up noise off air and amplifying it.

More resolution ? A modulator modulates the existing video, audio and sync signals to an Radio Frequency signal. This was always needed when TV's were just used as TV's. If you now have source putting out composite video (or preferably RGB) the modulation and de-modulation in the TV is reducing the quality of the picture a lot. Wether there is noise from other stations or not, the process itself is reducing quality.

Peale, that sounds the way to go. Check voltage levels though. Also, you need the sync signal somewhere. RGB is by far the best option. Bypasses everything, you're directly steering the guns with that signal.

[SirPeale]

Which would be great for a 13" arcade monitor, but I want it to run a Jakks.  They don't output RGB.

[Level42]

Which would be great for a 13" arcade monitor, but I want it to run a Jakks.  They don't output RGB.

Post 19 and 21 confuse me...do the Jakks have RGB somewhere or not ? Probably not I guess...

[richms]

More resolution ? A modulator modulates the existing video, audio and sync signals to an Radio Frequency signal. This was always needed when TV's were just used as TV's. If you now have source putting out composite video (or preferably RGB) the modulation and de-modulation in the TV is reducing the quality of the picture a lot. Wether there is noise from other stations or not, the process itself is reducing quality.

Peale, that sounds the way to go. Check voltage levels though. Also, you need the sync signal somewhere. RGB is by far the best option. Bypasses everything, you're directly steering the guns with that signal.

yes, more resolution then an arcade machine - they are what - 300x240 on a good day, thats VHS resolution at 300 lines - RF is capable of way more then VHS, especially when you consider that consumer grade modulators dont filter the input down either there should be no worries. the jakks may have a bit more since its showing a vertical game in the middle of a horizontal screen, but I doubt it will make much difference.

When playing a VHS I can see no difference between RF and composite - I can on a digital sat receiver looped thru the VHS deck but thats to be expected. If I connect the antenna in to the VCR then I can see some noise which is coming in via the antenna affecting the picture. I guess I could retune the RF out to a more clean channel but I lack a spectrum analyser to see which one is better, same with the modulator in the sat box, I changed that to ch 34 so I can run it and the VHS to a splitter to more then one tv, at the end of it the picture is still fine, as long as I dont try to mix it with the off air reception.

[SirPeale]

Which would be great for a 13" arcade monitor, but I want it to run a Jakks.  They don't output RGB.

Post 19 and 21 confuse me...do the Jakks have RGB somewhere or not ? Probably not I guess...

Jakks don't output RGB, they're composite only.  AFAIK no way to get them to RGB.  I don't know if you've ever opened one up, but they're very simple devices inside.  One tiny little chip IIRC.

I was saying I could do RGB on this because I noted the RGB outputs on the chip.  Theoretically I could hook an arcade PCB to it.

[Level42]

I see. Yes, I've opened up my Ms.Pac Jakk to see if there was an easy way to get it from NTSC to PAL. No dice.....bought a couple on my last holiday in the US. Too cheap to leave there

Games work ok here, but f.i. red is purple.....

[richms]

I got one locally in NZ and it was ntsc as well.

I solved most of the issues with it looking crap by turning off all the digital stuff on the picture menu of the tv - Digital comb filter was the worst offender, and something to do with the sharpness also made edges look pretty munted. Im guessing they dont but much effort into composite decoding on current tvs since thats hardly used anymore.