32X S-Video Mod

[villahed94]

This: http://www.jrok.com/hardware/RGB.html

I know it cost a lot, but it works as is and even has POTs to adjust the color balance to make sure everything comes out right. I have never had a complaint with this adapter.

Have you disassembled the unit to see if the chip that board uses has a part #?

[evildragon]

All part numbers have been scratched off. Unreadable.

[villahed94]

You could take a picture of it. A good enough picture might be enough to guess.

[evildragon]

Ok. Ill get it tomorrow.

[OGHUGO]

Hey,

I'm not sure if this is well known info, but I couldn't find any info on it, and found lots of contradicting and false info various places (and maybe my searching just sucks). I certainly don't claim to be a Genesis expert... I just figured I'd post some info and pics of what I did in case it helps anyone. This place seems to the be the place to discuss all things Genesis.

Anyway, I finally picked up a Sega CD, and the proper cables for a 32X, so I decided to get it properly set up in my entertainment center. I was testing a few Genesis systems, trying to hear differences between different versions. But while doing that, I noticed on one of them that the video quality sucked (surprise... opened it and saw the KA2195D)... but when I connected it through the 32X, it looked much better. I also had a bad 32X cable, which caused lack of red. From these observations, I determined that the 32X must have a video encoder (not just overlay), bringing RGB from the Genesis (not composite).

Then I got thinking about S-Video, so last night I probed around a little bit with the scope and saw seperate Y and C. Y is output on pin 22, C on pin 17, on IC12, though those are unfiltered, and look bad if used directly (ghosting, etc). They're actually filtered externally and fed back in on pins 21 and 19 (respectively), which is then mixed in the chip and output as a composite signal. Those are the pins you want to use (well, more convenient points on those nets).

Like most of these ICs, you can't use the Y/C signals directly... you need to amplify them. I used the simple emitter follower amps... an NPN (2N3904) and resistor (+5V to both Collectors, Y to one Base, C to the other, and output resistors from the Emitters). I found a value of 100 ohms on the output made the S-Video look similar in brightness/color to the composite (though I didn't do extensive tweaking), and the signal levels looked good on the scope.

To mount it, I took the two transistors, soldered the collectors together, clipped and bent the legs to the proper length/shape, then epoxied them to the top of IC12. Then I soldered them to the proper points (Y to the back lead of the unpopulated R46, C to the front lead of C77, +5V to the front lead of C80).

Anyway, the picture looks great, and it's really easy to do. You can continue to use the existing composite off the A/V cable with this mod, and that cable is still used for audio. I haven't decided how I want to mount the connector (I'd really like to make a Neptune-like system if I get the time), so for now, the video is just connected with jumper wires.

Attached are some pics of the install, and a couple screenshots. Unfortunately, it's really tough to get good pictures of the TV w/ my camera (bad moire). But you can see clarity vs. lack of clarity between the pictures, and I'm sure you all know the difference in quality between composite and S-Video. The TV also has a 3-line comb filter on the composite input, which already improves the image over a normal TV. I only posted one comparison pic, but of course it also works similarly for the Sega CD and 32X.

I don't know how good this encoder is compared to an external one driven from RGB, but this one is already there and easy/cheap to use. It's clearly MUCH better than the KA2195D. If anyone does, or has done this mod as well as an external encoder, I'd be interested in seeing the difference.

Here's the points to connect to:
Attachment 2803

Epoxy and heatshrink:
Attachment 2804

Hooked up and running:
Attachment 2802

Screenshot of composite through 32x:
Attachment 2805

Screenshot of S-Video through 32x:
Attachment 2806

DogP

Hey guys I followed this guide however it looks kinda dark and too many jailbars.. any way to fix this.? My svideo coming out of my genesis looks way better than this. Should i remove the NPN (2N3904) from the chroma? i have 2 NPN (2N3904) each going to a 75Ohm resistor to the s-video jack.
Please let me know thanks
Here is what my 32x looks like I added a/v jacks and svideo to the back.
http://www.oghugo.com/ebay/32x/32x.JPG

[villahed94]

There is an improved circuit that makes it look even better, mostly because it bypasses some capacitors and resistors.

[Drakon]

Hey guys I followed this guide however it looks kinda dark and too many jailbars.. any way to fix this.? My svideo coming out of my genesis looks way better than this. Should i remove the NPN (2N3904) from the chroma? i have 2 NPN (2N3904) each going to a 75Ohm resistor to the s-video jack.
Please let me know thanks
Here is what my 32x looks like I added a/v jacks and svideo to the back.
http://www.oghugo.com/ebay/32x/32x.JPG

Composite video still wired up means you did it wrong. Don't know how you managed to get jailbars. I use 50 ohms on luma.

[OGHUGO]

Composite video still wired up means you did it wrong. Don't know how you managed to get jailbars. I use 50 ohms on luma.

So the chroma should i remove everything and just have it straight to the jack and change the 75 ohm to a 50 ohm resistor on the luma?
I did not disabled the composite since someone on this tread said it didnt need to be removed.
Let me know. Also is it possible to get a pic of the inside of your 32x so i can see what you are talking about?
Don't really know how to read schematics so i can follow a picture more than I can do that.
Thanks in advance !
--OGHUGO

[OGHUGO]

I have connected the croma directly to the jack, removed the 75 ohm resistor and replaced it with 1 33 and 1 22 to = 55 ohm, i didnt have a 50. still doesn't look as sharp vs my modded svideo genesis

I took some pictures here.
This one is svideo coming from the 32x
http://www.oghugo.com/ebay/32x/32x-svideo.JPG
this one is svideo coming from my modded genesis
http://www.oghugo.com/ebay/32x/gen-svideo.JPG

as you can see the 32x is a bit blurry..
let me know if there is anything I can do thanks.
--OGHUGO

[evildragon]

Oh jesus, an HDTV CRT with upscaling to 540p.

I'm sorry, I just noticed what kind of TV we are dealing with. I had one of these, and found the only way to get them to look good, was with Component video.

Now that just may have been mine, but I never got good S-Video out of mine.

[OGHUGO]

Oh jesus, an HDTV CRT with upscaling to 540p.

I'm sorry, I just noticed what kind of TV we are dealing with. I had one of these, and found the only way to get them to look good, was with Component video.

Now that just may have been mine, but I never got good S-Video out of mine.

Its a Sony KV-32HS420 720P crt.
Everything looks great on it even my first gen svideo modded genesis.
I recently got all RGB cables and scart rgb to componet upscaler they look really good. Just trying to mod this 32x for my friend.\
I have my own with RGB cable no other way to play i tell ya.
This tv also has hdmi connector in the back i just wished my receiver would accept 240 signal so it can upscale it to 720.
But any how let me know what you think and see if there is anything I can do.
Thanks

[OGHUGO]

I have connected the croma directly to the jack, removed the 75 ohm resistor and replaced it with 1 33 and 1 22 to = 55 ohm, i didnt have a 50. still doesn't look as sharp vs my modded svideo genesis

I took some pictures here.
This one is svideo coming from the 32x
http://www.oghugo.com/ebay/32x/32x-svideo.JPG
this one is svideo coming from my modded genesis
http://www.oghugo.com/ebay/32x/gen-svideo.JPG

as you can see the 32x is a bit blurry..
let me know if there is anything I can do thanks.
--OGHUGO

No responses.. I was also thinking of doing the same thing i did with the genesis model 1, using the damomonster.com walk through will this work? Need help guys..
please let me know thanks.

[Drakon]

So the chroma should i remove everything and just have it straight to the jack and change the 75 ohm to a 50 ohm resistor on the luma?
I did not disabled the composite since someone on this tread said it didnt need to be removed.
Let me know. Also is it possible to get a pic of the inside of your 32x so i can see what you are talking about?
Don't really know how to read schematics so i can follow a picture more than I can do that.
Thanks in advance !
--OGHUGO

Learn to read a schematic. The image is blurry because you didn't disconnect luma from the filter circuit which removes composite video but fixes the sharpness.

Here's the image with luma connected to the circuit generating composite video, as well as filtering the luma into a blurry mess:



Here's the same image after you disconnect luma from that stupid circuit:



Here's how it looks on a tv when done right:





I posted the schematic in a number of different places. If you don't want to learn how to read my very easy to read schematics then you're pretty much saying you don't want to learn how to do this right. For learning how to read a schematic just do what I did, ask google, or you can hire someone.

If you want to believe every post you read in a thread including "leaving the composite circuit connected is fine" then you're going to have a difficult time. For example my sega genesis can shoot laser beams by adding a resistor on the audio circuit. I posted it, therefore it must be true.

[OGHUGO]

Learn to read a schematic. The image is blurry because you didn't disconnect luma from the filter circuit which removes composite video but fixes the sharpness.

Here's the image with luma connected to the circuit generating composite video, as well as filtering the luma into a blurry mess:



Here's the same image after you disconnect luma from that stupid circuit:



Here's how it looks on a tv when done right:





I posted the schematic in a number of different places. If you don't want to learn how to read my very easy to read schematics then you're pretty much saying you don't want to learn how to do this right. For learning how to read a schematic just do what I did, ask google, or you can hire someone.

If you want to believe every post you read in a thread including "leaving the composite circuit connected is fine" then you're going to have a difficult time. For example my sega genesis can shoot laser beams by adding a resistor on the audio circuit. I posted it, therefore it must be true.

Hey thanks for the reply I got it working. I followed your own suggestion in a different post. You could have easily have pointed to this to avoid all confusion.
Anyways here is your post with the actual picture. It even says "Also many thanks to tiido for making that very helpful 32x encoder schematic that nobody seems to be able to read." nobody including me then i saw your picture.
http://www.sega-16.com/forum/showthr...l=1#post491827