LM1203 for CRT hacking

[segasonicfan1]

Hey folks,
  I had an idea for doing some CRT RGB video conversion...where I live you see CRTs dumped on the street all the time for free, good ones too. So I want to build a circuit that will convert these into RGB monitors.  The LM1203 seems like a great easy way to do this, and it appears to be used in quite a few arcade chassis.  Anyone have experience with these before?  The datasheet seems remarkably straightforward and the part count is low.  My only concern is really getting the back porch timing right and making sure the amplifier stage is on the neck board (it usually is) so I can feed the LM1203's outputs to there. 

For sync, I was thinking I could just feed that into the composite input and onto the jungle IC built into most all CRT's  separate the RGB out from the jungle IC, attach the LM1203 and voila, RGB goodness.

It sounds a little to easy to be true, am I missing anything?  I know you guys really know your stuff here.

-Segasonicfan

[jennifer]

    Your on the right track, But its not that easy.... First the tv in question may have either a high or low ohm resistance horizontal coil, (And trust me) if you change that yoke winding (even if you can) you are in for a long ride to get the convergence right again ( notice I said right, all you eyeballer "super tecs" out there) ... My second concern would be the neck pins not all tubes are the same. so (IMO) at the very least your looking for a specific monitor.

[pbj]

Meh do it anyway. 

[Paradroid]

I had an idea for doing some CRT RGB video conversion...where I live you see CRTs dumped on the street all the time for free, good ones too. So I want to build a circuit that will convert these into RGB monitors.

I've gotten deep into this over the last couple few months and have already converted about 5 standard CRT TVs to dedicated RGB monitors. In fact, I have already gutted two 20 inch Philips TVs (Philips chassis and Panasonic tubes) that fit perfectly into my New Zealand made cabs. The way I wired things, they are completed dedicated to RGB. No need to switch to the AV channel or other hassles. I inserted RGB and Sync directly into the Jungle IC.

To achieve this I spent weeks reading every scrap of information I could find on the subject. It turns out that the process is surprisingly simple if you have a Jungle IC that accepts a standard RGB input (and many do!). The other crucial steps (to achieve good image quality) are the 75 ohm termination and DC coupling.

I'm planning on putting together a guide sometime in the future (with all the relevant links and pieces of information I bookmarked along the way).

In the meantime, you can check out the end result here and here.

I certainly admire your enthusiasm... many people have claimed this kind of mod isn't worth bothering with but, based on my own success, I would say it's totally worth pursuing! However, I'd definitely recommend trying the OSD interception method before trying to design a more complicated circuit.

If you're keen to try, I can try prioritize my write-up in exchange for some proofreading and reporting back on your own results.

[segasonicfan1]

wow, thanks for the super quick replies!

    Your on the right track, But its not that easy.... First the tv in question may have either a high or low ohm resistance horizontal coil, (And trust me) if you change that yoke winding (even if you can) you are in for a long ride to get the convergence right again ( notice I said right, all you eyeballer "super tecs" out there) ... My second concern would be the neck pins not all tubes are the same. so (IMO) at the very least your looking for a specific monitor.

Let me explain this a little better:  I'm not going to be messing with the yoke or anything like that at all....I want to use the stock circuitry for ALL sync stuff.  I'm going to input sync through the stock composite input.  I'm just trying to tap the RGB wires from the neckboard - not the tube neck pins and all that.  I'm going to use the stock high voltage transistor amps that are on the neck board.  Just feeding a preamp RGB level to them from the LM1203. 
From what I understand it seems pretty straight forward.

I've gotten deep into this over the last couple few months and have already converted about 5 standard CRT TVs to dedicated RGB monitors. In fact, I have already gutted two 20 inch Philips TVs (Philips chassis and Panasonic tubes) that fit perfectly into my New Zealand made cabs. The way I wired things, they are completed dedicated to RGB. No need to switch to the AV channel or other hassles. I inserted RGB and Sync directly into the Jungle IC.

To achieve this I spent weeks reading every scrap of information I could find on the subject. It turns out that the process is surprisingly simple if you have a Jungle IC that accepts a standard RGB input (and many do!). The other crucial steps (to achieve good image quality) are the 75 ohm termination and DC coupling.

I'm planning on putting together a guide sometime in the future (with all the relevant links and pieces of information I bookmarked along the way).

Thanks for your post, that sounds terrific!  Actually, I have done the jungle IC hacks before. Here's the 2 I successfully did it on:
http://nfggames.com/forum2/index.php?topic=5471.0
http://nfggames.com/forum2/index.php?topic=2814.0

Thing is, I want to use the LM1203 on the first monitor, the KV-9PT60.  It's a wonderful little 9" CRT but the Jungle IC does NOT take analog RGB easily.  Requires BS I2c programming stuff.  Hoping to bypass it with my own circuit to feed RGB to the guns.

This project might take a bit since I'm going to practice on another CRT first and have another project for a customer.  But I want to do it soon, within the next month   I'd love to proofread your write-up then !

-Segasonicfan

[Paradroid]

Actually, I have done the jungle IC hacks before.

Awesome! I hadn't seen your posts before now but I'm looking forward to reading them in detail. I'll link to them in my guide.

Very keen to see how your idea works out... definitely keep us updated!

[nitrogen_widget]

Even though I went to school for electronics in another life, high voltage CRT TV's scare the crap out of me.
Projection CRT TV's only slightly less scare me.

And while just about all the terminology in this thread went over my head i'm like a highly trained monkey that can follow technical instructions rather well

At this point a VGA to S video adapter box off ebay for $15 is actually good enough for me but if I can get a better picture without too much hassle or cost i'd definitely be interested in hearing more since CRT TV's go from free to $50 for the 36" monsters at the thrift stores.