S-video 32X

**Lum** · 03-20-2012

Either should be a great improvement. Not that that's saying much. We all know about the negative reputation Genesis style composite has...

Keep in mind external RGB to s-video encoder boxes are scarce and expensive.

It actually costs less to get an RGB to component one, assuming one's setup can handle that. Despite component having more quality potential.

**Druid II** · 03-20-2012

The CXA1145 in the Megadrive can do s-video and it's fairly trivial to add an output for it.

The 32x uses a custom Sega chip that mixes together the Megadrive video and the 32x video. Apparently it DOES have s-video output pins, but something fishy is going on there, it's looped back to form composite, or some such crap (no idea). If there's absolutely no way to grab a working s-video signal from it (which I doubt), it's still possible to add another video encoder that grabs the final RGB picture and generates s-video from it. But like it was mentioned before, space inside that plastic mushroom could be a problem.

I'd check the output pins on the video encoder first, to see if it does or does not encode proper y/c signal to use.

**APE** · 03-20-2012

I'll be getting a 32x shortly here so I can at least play around with S-Video on my CRT to see how it looks compared to composite. The difference is readily apparent on a 32" display.

Wish I had an oscilloscope to check it out.

**veganx** · 03-20-2012

APE,

Since you have far more knowledge then me, if you can work an s-video out of it, can you post some kind of tutorial?
Maybe some pictures during the process to show where to cut and where to solder.

**APE** · 03-20-2012

Originally Posted by Druid II

The CXA1145 in the Megadrive can do s-video and it's fairly trivial to add an output for it.

The 32x uses a custom Sega chip that mixes together the Megadrive video and the 32x video. Apparently it DOES have s-video output pins, but something fishy is going on there, it's looped back to form composite, or some such crap (no idea). If there's absolutely no way to grab a working s-video signal from it (which I doubt), it's still possible to add another video encoder that grabs the final RGB picture and generates s-video from it. But like it was mentioned before, space inside that plastic mushroom could be a problem.

Out of the 2-5 S-Video circuits I've built and used on the CXA1145 I've not found one that works universally without trouble on every TV tested on. Have had trouble with a JVC X'EYE specifically; found a 6th I need to test out. Seems using a transistor+resistor to amplify luma just isn't enough for some displays.

I'm not too sure I follow what you mean about being looped back to form composite. I don't have intimate knowledge of the internals of the 32x mind you but from that thread above it looks like luma and chroma are being pulled out and amplified with a PNP transistor and a 100ohm resistor. Having a bit of trouble interpreting the images available in that thread as well but that'll clear up as soon as I have this 32x in pieces. Thing is every circuit I've seen for amplifying S-Video has used a NPN transistor.

And so long as you're getting luma and chroma seperated I'm not too sure how it wouldn't be 'proper' luma/chroma either. Personally I'd find it a PITA to install a CXA1645 or equivalent to take the RGB and output it as S-Video. Probably enough room if you used surface mounted components but it'd be a bit pricy.

Originally Posted by veggav

APE,

Since you have far more knowledge then me, if you can work an s-video out of it, can you post some kind of tutorial?
Maybe some pictures during the process to show where to cut and where to solder.

If it works I could. I tend to make things ugly for testing purposes and pretty them up before I put everything together which makes me hesitant to put tutorials together. I can make an exception.

**Druid II** · 03-20-2012

Out of the 2-5 S-Video circuits I've built and used on the CXA1145 I've not found one that works universally without trouble on every TV tested on. Have had trouble with a JVC X'EYE specifically; found a 6th I need to test out. Seems using a transistor+resistor to amplify luma just isn't enough for some displays.

Yeah, but the 32x does not use a cxa1145, it has its own video encoder. Apparently. I don't know. Looking at the pcb and some pinouts I found, the audio goes straight from the MD input to 32x output, while the RGB, composite, and c-sync are led down to a custom sega chip.

Originally Posted by APE

I'm not too sure I follow what you mean about being looped back to form composite.

I was just mentioning what I saw discussed on some of the sega-16 threads. I don't have a 32x so I've no clue what's going on inside the thing, and I don't care that much to construct theories based on online PCB shots. If I had a 32x, I probably would've tried soldering s-video on it already.