I need some help from you guys. Adding RGB inputs to CRT

Hey everyone,
Some of you may have seen this sweet 1984 Mitsubishi console television I came up on in the chat room when I was first showing it off. Anyway, I tore it all down and dusted it out and re-assembled it and now that I've been all up inside of her I feel comfortable to try some modifications. I've been spoiled by my Sony PVM RGB inputs and I would really like to enable RGB inputs on the Mitsubishi. I know it can be done if I tap into the right place on the board. Here's some pics:




The good thing is I have the original service manual with full schematics of the entire TV. Here is a picture showing the IC chip where the RGB signal is being converted to composite then sent out to the CRT board where it gets broken down to RGB again to the tube. I was thinking I could add a switch between the IC chip and the CRT board and feed raw RGB signals to the CRT.



Please take a look at this picture and let me know what you think. If there are any other parts of the schematic you would like to see let me know and I will get pics posted.

Thanks!

 

Dude! That TV is mint!

 

Be careful working on CRTs awesomeNES. They can kill you, send you flying across the room (literally), or both at the same time. It's usually both. Please be careful!

 

http://mikejmoffitt.com/wp/?p=284

I think this technique may be the way to go. If anyone else finds any good posts from the web on this topic please post it up. It would be good if we could come up with a way to make any crt have RGB inputs!

 

I'd follow mbj's advice. Unless you have a discharging probe (which are scarce) I would not suggest fiddiling with that TV. modern crts have a feature to discharge once the power is off but sometimes it doesn't work and may kill you at any moment. Also when you get the probe always use one hand!

 

Seph, I have a high voltage probe for my multimeter. I'm well aware of how to discharge a CRT. There's some basic rules:
When working on a cold chassis, always discharge the CRT before sticking your hands inside.
When working on a hot chassis, always use an isolation transformer (which I also have) and only work with one hand inside the TV.
I really appreciate you caring about me, but don't worry I got it covered and I've already completely taken the TV apart to clean everything and put it back together.
Here she is all taken apart:





I personally don't think CRT is that dangerous as long as you're careful. CRTs were the common standard in television not too long ago and many people worked on them and didn't die.

Lets get this baby displaying RGB!

 

you mean a flat head screwdriver and a thick piece of wire

 

You should see her now after I've used some orange oil and polished up the wood. It got rid of those dry spots and the grain has a nice depth to it now, and it smells nice!

Lol, you don't even need a thick piece of wire. An alligator clip wire connected to ground on one end and the screwdriver is fine, but be prepared for a big arc because there's no resistance in between. The probe makes a hissing sound and slowly discharges, whereas the simpler way just zaps the stored power right out like a stun gun. You can get away without a high voltage probe, but if you wanna take measurements then you need it.

 

Awesome mod if you can pull it off,I want to do the same to my sony trinitron,just haven't got around to it.

Here is some nice info on adding rgb to a standard tv.
http://nfggames.com/forum2/index.php?topic=4159.0

 

I got excited about this project and EVERY SINGLE comment was about discharging the CRT.
Can we move on an talk about where on the board we need to tap in? and if an amp would be needed.

 

I agree. CRTs are not as dangerous as people think, especially if you take the standard precautions.

 

I read page you linked earlier and I could almost understand what he did, but given the fact that TV's are so different, there won't be an easy guide to do this.

 

I'm consulting some other people on 2 different forums dedicated to TV and radios. I will report back here with information I learn from those dudes.

 

Need to see more of the schematic.
Whats the IC No?

 

Did you ever finish this? It's the first time I've heard anyone attempt a hot chassis mod.

 

NO, I haven't yet. I'm currently away at school, but I still own the TV and one day I will get back in there.
Thanks for your interest.

 

I don't think that's a hot chassis design - first of all, it has AV inputs and secondly the transformer looks big enough to run a TV that size without having to directly use line power.

I suspect the biggest hassle is going to be that judging from the part of the schematic that was posted it uses a hybrid drive approach with Y fed into the emitters of the grid drive transistors and color difference signals fed into the bases. I also suspect that the brightness and contrast controls are adjusting the gain and offset on that Y drive signal.