Sega 32x perfect s-video mod

[Drakon]

I won't bore anyone with all the little details.

 

 

Video of the super sharp s-video modded 32x in action

 

[Hatta]

Please bore me with all the little details. Does this pick something chroma/luma like off the chip, and convert it into proper chroma luma, or are you converting RGB to YC? What's that bunch of capacitors with an inductor in the middle do?

[the.golden.ax]

Please bore me with all the little details. Does this pick something chroma/luma like off the chip, and convert it into proper chroma luma, or are you converting RGB to YC? What's that bunch of capacitors with an inductor in the middle do?

 

Seconded.

[Rex Dart]

Lay those sweet boring details on me, man. From what I'd read before, the video chip in the 32x doesn't put out separate chroma & luma signals.

[atarifanboy1980]

Yea I want details on it too .

[Hatta]

Oh I clicked through to Drakon's site, and found the thread where he discusses it. Chroma/luma is available right off the chip but luma needs to be amplified or it won't work. The amp is just a transistor.

 

If I understand correctly, the penciled in stuff is already on the Genesis PCB. All the mod really is is disconnecting one pin, sending it through the amp, and hooking that and another pin up to an svideo port. Click to the thread and read Drakon's excellent step by step. I'm going to try this one.

Edited June 13, 2012 by Hatta

[Rex Dart]

Oh I clicked through to Drakon's site, and found the thread where he discusses it. Chroma/luma is available right off the chip but luma needs to be amplified or it won't work. The amp is just a transistor.

 

If I understand correctly, the penciled in stuff is already on the Genesis PCB. All the mod really is is disconnecting one pin, sending it through the amp, and hooking that and another pin up to an svideo port. Click to the thread and read Drakon's excellent step by step. I'm going to try this one.

 

Huh, that's pretty much exactly the same as the standard Genesis mod, then. I wonder why I'd been reading that it was so much more complicated to s-video mod a 32x.

[Hatta]

I think no one knew just what a 315-5788 chip was, until that guy on Sega-16 did some checking with an oscilloscope. Someone concluded that the lack of knowledge meant it couldn't be done, and that was the prevailing wisdom until someone actually looked.

[Rex Dart]

Ah, I bet you're exactly right.

[Drakon]

*necrobump*

 

Sorry I didn't check this forum very often. Yes luma and chroma come straight off the chip. Whoever discovered there being luma and chroma coming from the chip found it out quite a long while ago, but the guy didn't design the circuit properly resulting in a very blurry picture that wasn't much better than composite video. Tiido took the time to draw a diagram of the circuit of the video chip in the 32x and after studying tiido's diagram I decided to disconnect the luma from the existing circuit because and blur would be caused by the luma line not chroma. Sure enough disconnecting luma from the on board circuit made the picture go crystal clear, most likely the blur was caused by the luma line having a capacitor connecting to ground but I disconnected the entire circuit just for the heck of it. According to tiido the video encoder chip in the 32x is a custom rohm encoder that was only used in the 32x so no documentation for that video encoder seems to exists. Nobody seems to have actually messed with the 32x video encoder chip very much. When my first 32x arrived in the mail within 2 hours I went from believing that you can't s-video mod the 32x to coming up with a perfect s-video circuit for it. I was fully prepared to take the rgb from the system and externally encode that into s-video. However after doing a little google digging I discovered that someone had found out that the built in chip already has luma and chroma and the guy just didn't know how to wire up the circuit properly.

 

The 32x actually outputs s-video quality that's superior to the s-video mod in a genesis, even with just genesis games. The "penciled stuff" is the video encoder chip found in the 32x, tiido likes to draw things in pencil for some reason. The method is easy, disconnect a zero ohm resistor on the luma line from the chip, connect the luma and chroma pins, build your 1 transistor amp for luma, wire them into a s-video jack.

 

Who knows, maybe the encoder in the 32x is nothing special and having an inductorn and / or capacitor connected to ground on the chroma line is what makes the s-video look so great.

Edited September 28, 2012 by Drakon

[driph]

*Rise from your grave*

 

 

 

Has anyone done this mod yet? What were your results?

[iesposta]

I did it recently. Very happy with the S-Video output. There is, however, slight jailbars (vertical lines), but the composite cable was unplayable before.

Mine is this first Genesis model, with the desirable "no DRM" (Non-TMSS something), with the "undesirable" non-Motorola chip, but had 100% success.

There are images in my gallery:

http://www.atariage....a-genesis-mods/

I was going to make a detailed how-to post, but just didn't get to it.

I also added an overclock chip with "select overclock / select original clock switch" to reduce slowdowns, and changed the LED color. I have since changed the blue LED to a bright orange.

 

EDIT: I have in my gallery, the circuit for the easier to find 2N 3904 Transistor.

Note: The capacitor can be wired either way, I know it is polarized, but there are designs showing connection both ways and in my tests there is no difference. The jailbars may be reduced by different values of resistors, but I used what I found in my scrap and it doesn't bother me.

 

EDIT EDIT: Oh, duh, this is the 32x Mod.

I did that too. With the same parts 2N3904 (probably a bit different resistor values, but close). I don't have pictures of that, it was a bit harder to solder the wires to the tiny points of the surface mount chips of the 32X, and removing that zero ohm resistor jumper. Actually the picture out of this mod is even nicer than the Genesis S-video mod, I would guess because the parts are newer and the design is newer (not like the first run original Genesis hardware).

Edited December 3, 2012 by iesposta

[Drakon]

Uhm, those are pictures of the genesis s-video circuit not the superior 32x one discussed and posted in this thread.

 

Oh I see you edited that info in after haha.

Edited December 5, 2012 by Drakon

[driph]

This would be a good project for a walkthrough, s-video on a Genesis at all is great, but the 32X deserves to shine as much as possible (especially given the somewhat lackluster library). :]

[Drakon]

This would be a good project for a walkthrough, s-video on a Genesis at all is great, but the 32X deserves to shine as much as possible (especially given the somewhat lackluster library). :]

 

What's a walkthrough?

[the.golden.ax]

Step by step Lego style tutorial on how to do it yourself.

[Drakon]

Step by step Lego style tutorial on how to do it yourself.

 

I can provide text instructions but I'll need someone else to take pictures and circle the parts I'm talking about.

[driph]

Replied to your PM, I'll help ya put something together.

[Drakon]

Okay here's my rough instructions.

 

Step 1: open the 32x

Step 2: remove the screws that will allow you to take off the rf shielding, put these screws someplace you won't lose them

Step 3: Locate the video chip labelled "sega 315-5788"

Step 4: Desolder the 0 ohm surface mount resistor that connects to the video chip pin which is located on the top row six pins from the right. To desolder a small surface mount resistor just add enough solder to connect both sides at once and then it should just come right off.

 

Step 5: Once the 0 ohm resistor is removed solder a wire to the solder pad left from where the resistor used to be. There will be two solder pads left, one pad connects to the video chip and this's the pad you want to solder your wire to. Make sure that where the 0 ohm resistor used to connect remains disconnected otherwise you'll get a very blurry image.

 

Step 6: On the top row of pins third from the right follow the trace connecting to that pin and solder a wire to the first surace mount capacitor that connects to this trace. I recommend soldering onto the side of the capacitor that connects to the video chip

 

Step 7: Find a place to solder both +5v and ground to. Ground should be easy to find, 5v I soldered a wire to the multi av connector which required me to pull out the 32x pcb entirely and remove the rf shielding underneath. If you wire 5v to the multi av connector you can also wire ground to the connector by downloading the pinout and figuring out which pins are the ones you want. Once you find your 5v and ground location solder separate wires to each location.

 

Step 8: Get your hands on a npn general purpose amplifier transistor, for this project I used the 2n3904. The 2n3904 is very common and easy to buy.

 

Step 9: Find the datasheet for your transistor and locate the base, collector, and emitter pins.

Step 10: Once you've figured out the pibout of your transistor stick the legs through a small piece of breadboard, solder the legs in and clip the extra leg length to make the transistor as small as possible.

 

Step 11: Solder +5v into the collector pin of your transistor, solder the wire connecting to where you removed the 0 ohm resistor to the base pin of your transistor, and solder another wire to the emitter pin of your transistor

 

Step 12: Buy a s-video female jack, choose a place to install this jack into your 32x.

Step 13: Solder the emitter wire from the transistor into the luma pin of your s-video jack

Step 14: Solder the wire connected to the other pin on the video chip to the chroma pin of your s-video jack

Step 15: Solder all the ground pins of your s-video jack together (there should be 3 of them) and solder your ground wire to all the grounds.

 

Step 16: Install your s-video jack somewhere, you can drill a hole somewhere and install the jack or you can do what I did and desolder the multi av output port and glue the s-video jack into that location.

 

Once everything is working I recommend you hot glue down your wires so you don't short the console. Covering the exposed metal of the 5v wire is the most important.

Edited December 7, 2012 by Drakon

[Smoke Monster]

Nice work Dracon, and thanks for the writeup.

 

How does the quality of the s-video output from your mod compare to scart RGB output?

[iesposta]

The picture drawing has gone.

It was similar to this.

Chroma can be direct, no cap or resistor from the 32X.

[Uzumaki]

Mind you if you remove one resistor from 32x to get clean S-Video, you'll lose composite video. Just a heads up as some newer TV doesn't offer S-Video as it wasn't well supported in USA. These day it's composite, component, or HDMI.

[iesposta]

Mind you if you remove one resistor from 32x to get clean S-Video, you'll lose composite video. Just a heads up as some newer TV doesn't offer S-Video as it wasn't well supported in USA. These day it's composite, component, or HDMI.

All my gear has S-Video. That's 2 CRT TV's, a 47" LCD, and Acer DLP Projector.

I wouldn't say "not well supported" but I would say "not used much by the masses."

RF or Composite was good enough for most people, even if they could hook up with S-Video, few bothered to do it.

 

I know that S-Video has been pretty much dropped.

Until someone designs circuits for HDMI output, the S-Video is so nice that I'll probably get better results changing S-Video to Composite with an adapter. (Need to try this sometime.)

Have you ever seen the composite on Sega Genesis model 1 High Definition Graphics? It is so bad I thought it was a broken system!

 

Also my experience with Atari 7800 RF, even going direct to a good tuner, was so bad I had to "mod upgrade" their outputs.

(Conversely, the RF from Atari 2600 Heavy Sixers, and RF from Bally Astrocade is so good, it looks like I'm using S-Video!)

[+-^CrossBow^-]

So I've a question on this...

 

I recently started to find all my wires and such for my 32x and was thinking about hooking it back up to leave attached once and for all. But, here are my questions...

 

My model 1 HDG Genesis is already s-video modded. I cut the RF modulator out but left the original AV out on the back. I assume leaving my original S-video circuit is okay since the AV out would be used to get video to the 32x. So, I need to build another genesis s-video circuit minus the resistor and cap on the chroma and wire that into the 32x. Then I'm reading you can remove the AV out on the 32x and replace with your s-video output there.

 

that much I got, now here is my question and I'm not sure anyone can answer this...

 

I also added RCA left and right audio outputs on my genesis 1. However, I didn't tap them off the headphone section. I tapped the audio directly off the yamaha chip to bypass all the filtering and get the cleanest sound. Since the 32x passes the audio from it into the genesis and the genesis is outputting all the audio, I'm going to guess that I can't use my RCA outs from the yamaha since I don't believe anything else other then direct left and right synthesis is coming out from that chip? In other words, the 32x audio channels aren't going through the yamaha synthesis. Therefore I'm guessing I wouldn't hear the additional sound channels from the 32x from my current RCA outputs?

 

Ideas?

[Rex Dart]

Are you sure it was the Yamaha chip and not the CXA1034 you tapped? Weren't there other chips capable of producing audio on that board that would need to be combined before sent out to speakers?

Anyways, sounds like you have practically everything needed to test it. Let us know what you find out.