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  • Joined: 11 Jan 2009
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Help with svideo mod in Master System III
Post Posted: Wed Jan 14, 2009 2:45 pm
Hello, this is my first post here, but I've been a reader of the site/forums for years.

Last weekend, I decided to try modding my Tec Toy Master System III (the first model, with Alex Kidd bult-in). I sucessfully did the region changing and the composite/audio ones, which gave me a superior image in comparsion with the RF, but I couldn't get the s-video mod - the one I wanted the most - to work properly. Since I read here that using the 200uf cap/75ohm resistor methode for the luma signal (like I did for composite and chroma signal) could get me some strangeness in a few games - like the AKMW title screen, etc - so I tried to mount the sonicsegafan circuit. I can get no s-video image with it, however. Every connection seems to be right, the chroma, ground and +5v volts included,tried a continuity test, the chip is the same (CXA-1145P), I soldered everything to the right pins, etc. I even took away the composite wires and tried the luma signal with the 220uf/75ohm connection, and it worked fine with cartidges - Phantasy Star is simply beautiful with s-video - but the title screen of Alex Kidd is indeed messy, and there was also in the water stages some kind of interference and lack/"blink" of colors (it could be some interference of the RF, because it got weird too when tested while the s-video is connected).

I could go with this connection, but in addition of not getting a fully working AKMW, I also want to mod a Genesis next, and since it uses two of the segasonicfan's circuit according to the source I want to follow, I came here to ask you guys help in learning how to properly build it. I know next to nothing of electronics and this kind of stuff, but I can follow directions. Are there any wrong connections in the circuit, or even wrong components?

Thanks in advance!
mdmiii1.jpg (102.13 KB)
Please ignore the wire mess in the background...
mdmiii1.jpg
mdmiii2.jpg (97.21 KB)
Any wrong components?
mdmiii2.jpg
mdmiii3.jpg (85.05 KB)
Upper vision...
mdmiii3.jpg
mdmiii5.jpg (91.95 KB)
... with the connections
mdmiii5.jpg
mdmiii4.jpg (98.49 KB)
The soldering work is ugly, but nothing is shorted
mdmiii4.jpg

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Post Posted: Sun Jan 18, 2009 11:46 pm
Anyone?
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Post Posted: Mon Jan 19, 2009 5:51 am
My guess is you have the transistor in the segasonicfan circuit oriented incorrectly. Different transistors have the collector/emitter/base legs in different positions, so you should always look up a datasheet before you solder it in.
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Post Posted: Tue Jan 20, 2009 7:16 am
The best thing to do is pull modification out and throw it in the bin, where it belongs.

Build another pair of amplifiers from this circuit instead.


.           | +5v
.           |
.           |
.video   | / c 
.in   ---|<
.        | \ e
.      NPN  |   27   video
.           +--RRR--- out


NPN transistor type isn't too important, you can probably just use the ones you've got. I usually choose the BC548.

Only two components, as you can see. It's far more suitable than the other garbage one. Pin 15 is chroma out, 16 is luma out, and this circuit is only good for the CXA1145.
 
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Post Posted: Tue Jan 20, 2009 10:25 am
Two little components and it works better than that other one?! I bought the parts to redo my own SMS s-video mod the other day and would have put it together today if not for the heat. Good thing I checked here.
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Post Posted: Tue Jan 20, 2009 12:43 pm
That's right. The original amplifier circuit is a travesty. I could tell just by looking at it that both 110k resistors and the 0.1µ cap were 100% superfluous (try cutting them out and see for youself). The capacitive coupling seemed unnecessary as well and I verified this today. This new circuit is basicaly the same as the old one with all the useless crap removed.
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Post Posted: Tue Jan 20, 2009 1:07 pm
Does this only apply for the s-video outputs, or can that amp circuit be used for an RGB mod?
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Post Posted: Tue Jan 20, 2009 2:13 pm
albino_vulpix wrote
My guess is you have the transistor in the segasonicfan circuit oriented incorrectly. Different transistors have the collector/emitter/base legs in different positions, so you should always look up a datasheet before you solder it in.


Yeah, it was in the wrong orientation indeed... I put it in the right way and it solved (half) of the problem. When I power the console on, I got the SEGA screen and, for a second, the title screen of the game, then everything just phase out, leaving me only with sound. I tried it with the built-in game and several cartridges, and it was all the same. In one of my TVs, even the SEGA logo began to phase out. Thinking it could be something wrong I did when I desoldered the transistor, I even build a brand new circuit from new parts, but the result was the same. Anyway, thanks for the help, Albino! :-)

Viletim, thanks a lot, I'll try your circuit, just need to buy the 27r resistors. Does it matter the W value (1/3 W, 1 W, 3 W, etc) or can I buy any one of them? And since it can be used on the CXA1145, can it also be used on the Genesis mod?
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Post Posted: Tue Jan 20, 2009 11:05 pm
Corredor X wrote


Viletim, thanks a lot, I'll try your circuit, just need to buy the 27r resistors. Does it matter the W value (1/3 W, 1 W, 3 W, etc) or can I buy any one of them? And since it can be used on the CXA1145, can it also be used on the Genesis mod?


Any power rating you like is fine. Should be fine to use anywhere there's a CXA1145.


DMEnduro wrote

Does this only apply for the s-video outputs, or can that amp circuit be used for an RGB mod?


RGB requires a 220µ cap and 75 ohm resistor in series with each R,G,B output pin from the CXA1145, no amplifier as such.
 
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Post Posted: Wed Jan 21, 2009 6:04 am
Just tried the circuit on my SMSII. Even with a rather crude setup with crocodile clips, I'm happy to say that it works just as promised (and yes I tried the troublesome Alex.) Good work viletim!
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Post Posted: Thu Jan 22, 2009 1:15 pm
The new circuit worked like a charm, thanks again!
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Post Posted: Sat Jan 31, 2009 7:21 pm
Last edited by dhau on Mon Feb 02, 2009 4:02 pm; edited 9 times in total
Thank you, viletim. I did this mod using 2N3904 transistors and 33 Ohm resistors (the closest thing I had on hand). It works, but colors are wrong, especially white. I think the circuit output is a bit low on voltage. I'll probably end up buying variable resistors and see if I can get a better output.

Standard composite output

S-Video

Update: fixed S-Video with BC548B transistors (see posts below)
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Post Posted: Sun Feb 01, 2009 6:59 am
2N3904s like to do things backwards. Check the leg orientation. I also used the 3904s and they work great.
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Post Posted: Sun Feb 01, 2009 6:31 pm
I plan to replace 33Ohm resistors with series of 22Ohm + variable 10Ohm, and see if this helps.

If it won't help, I'll use different NPN general purpose transistors. I can salvage some BC547 from a junk PCBs I have.
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Post Posted: Sun Feb 01, 2009 8:23 pm
The first pics are all correct... maybe a bit too bright (a 47 to 75ohm resistor will fix it).
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Post Posted: Mon Feb 02, 2009 12:27 pm
dhau,

Those s-video pictures awful, something's wrong...

Watch out, different manufactuers of american (2N...) transistors have different pin configurations for the same transistor.
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Post Posted: Mon Feb 02, 2009 2:09 pm
viletim wrote
Watch out, different manufactuers of american (2N...) transistors have different pin configurations for the same transistor.


Thanks, I was thinking about resistors, but you are right. I inverted 2N3904, but it didn't change the quality of output, so I guess they where busted. I replaced 2N3904 with BC548B, and it worked properly. I'll update my previous post with photos to show new fixed S-Video output.

Here is how viletim's S-Video amp modification looks on my SMS (click for large pictures)



The switch is unrelated to S-Video part, it turns viletim's FM unit on or off.
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OT but still SEGA :)
Post Posted: Thu Feb 05, 2009 4:54 pm
As viletim says, this works on CXA1145M based JVC X'eye and CXA1145 based Sony MSX2 HB-F1XD

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Post Posted: Fri Feb 06, 2009 8:21 pm
Oh yeah, forgot to say: tried it on my Tec Toy Mega Drive I and it worked fine too, the image quality is amazing.
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Post Posted: Fri Feb 06, 2009 10:08 pm
Does anyone else have issues with faint vertical lines appearing when the screen has a light background? It is kind of like the ghosting you get with old NES-101 composite video mod.

If I'm not the only one getting faint vertical lines, then may be a more complex circuit would prevent those?

I own a Panasonic FS-A1GT, and it uses CXA1145 and outputs perfect S-Video, but it's output circuit is a lot more complicated. The service manual for it is available at MSX Info Pages.

viletim, could you please take a look at attached schematics and see why it doesn't have faint vertical lines? Thanks!

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Post Posted: Mon Feb 09, 2009 10:47 am
Sorry to hijack the thread but I've got a query of my own and couldn't find in searches if it had been asked before.

Is it possible to extract (or build) Y Pr Pb component video signals from the encoder chip? Since that is the format we use in Aus rather than RGB.
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Post Posted: Mon Feb 09, 2009 11:09 am
There is a Silicon Chip/Jaycar kit for converting RGB to YPbPr component. I have built one, and there seems to be a rather small amount of circuitry involved. It may be possible to recreate in system on a much smaller board. Just ask if you need more details.
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Post Posted: Mon Feb 09, 2009 11:29 am
Did a search/look around on their site but could not find such a kit.

However after reading the technical details of YPbPr it doesn't seem overly complicated, and the required signals are all present (Luma, R, G, B). I just need to work out what components are needed to do B - Luma & R - Luma or alternately split them out of the Chroma signal I geuss.
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Post Posted: Mon Feb 09, 2009 3:54 pm
dhau wrote
Does anyone else have issues with faint vertical lines appearing when the screen has a light background? It is kind of like the ghosting you get with old NES-101 composite video mod.

If I'm not the only one getting faint vertical lines, then may be a more complex circuit would prevent those?

I own a Panasonic FS-A1GT, and it uses CXA1145 and outputs perfect S-Video, but it's output circuit is a lot more complicated. The service manual for it is available at MSX Info Pages.

viletim, could you please take a look at attached schematics and see why it doesn't have faint vertical lines? Thanks!


Got those lines here too, in both Master System and Mega Drive. They're barely noticiable most of the time, but if you pay attention they are there. The blue sky of Sonic 2 opening is where you can see them the most. A small price for such a gorgeous image, I think :)
svdsmssg 065.jpg (620.25 KB)
svdsmssg 065.jpg

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Post Posted: Tue Feb 10, 2009 4:26 am
Just the NTSC (or PAL 60?) people see those lines then? Must be something related to the lines on the NTSC Mega Drive.

DMEnduro,
That Silicon Chip converter was designed with only Foxtel boxes in mind, it's not so good for general video game use.
 
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Post Posted: Tue Feb 10, 2009 6:13 am
viletim! wrote
DMEnduro,
That Silicon Chip converter was designed with only Foxtel boxes in mind, it's not so good for general video game use.


The reason for this is there is no sync input, right? There is some additional notes for the circuit involving an LM1881, but I can't easily get hold of one.
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Post Posted: Wed Feb 11, 2009 1:19 pm
DMEnduro wrote
viletim! wrote
DMEnduro,
That Silicon Chip converter was designed with only Foxtel boxes in mind, it's not so good for general video game use.


The reason for this is there is no sync input, right? There is some additional notes for the circuit involving an LM1881, but I can't easily get hold of one.


Nah, it's mainly because there's no DC restoration. Most game consoles output video with no DC component (capacitively coupled).
 
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Post Posted: Thu Feb 12, 2009 3:18 pm
viletim! wrote
Just the NTSC (or PAL 60?) people see those lines then? Must be something related to the lines on the NTSC Mega Drive.


Did the s-video mod on my PAL SMS2 and the lines are there also. They seem to be most visible in large blocks colour (especially darker ones as it helps contrast the lighter lines I geuss).
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Post Posted: Fri Feb 13, 2009 12:31 am
Just thought I'd add, I get lines on my PAL SMSII. I had them with the resistor/cap circuit, the segasonicfan circuit and this one. I suppose that's the CXA's way of saying "I don't actually support s-video suckers."
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Post Posted: Fri Feb 13, 2009 12:38 am
Dear viletim, sorry to bug you so much about S-Video and CXA chips, but can you please look at datasheets for CXA1145 and CXA1645 and tell if it is possible to solder CXA1645 instead CXA1145? I know that one is surface mount and the other is DIP package, but it's doable, however I'm not sure if circuitry around CXA1145 will work with CXA1645.

If this works, then we can have perfect S-Video.
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Post Posted: Fri Feb 13, 2009 1:54 am
An user at AtariAge forums - Longhorn Engineer - made a new version of his 2600 s-video mod that made these same lines that were in the old versions disappear, changing his circuit a little. Maybe something from the thread could help, here it is:

http://www.atariage.com/forums/index.php?showtopic=126434
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Post Posted: Wed Feb 18, 2009 5:28 pm
Wow, I dunno guys. I guess it's fun to hack your systems and all, but from the initial pics, it looks like the svideo did give a somewhat sharper image, but the colours look washed out. I ran into the same thing when I bought a combined cable for my ps1/gamecube it has both composite and svideo outputs. And while the svideo gives a sharper image on my LCD tv, the colours look bad. I think some 'blurriness' is necessary on old consoles to give richer colour, as they were designed for CRT SD tv's. I also visited a website where a guy did an svideo mod for his turbografx 16, and in the comparison shots between rf/composite/svideo, I do have to say that the composite ones looked best for colour, even if they are slightly blurred for Bomberman :P
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Post Posted: Thu Feb 19, 2009 10:17 am
I don't find mine are washed out at all. The only difference between s-video & composite is a sharper image and no bleeding (which after viewing on my HD LCD I now think there may be an issue with my AV mod as the ghosting/bleeding is quite extreme).

I did also use the exact same resistor value as suggested by viletim so possibly that makes some difference to washing out etc.
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Post Posted: Wed Apr 22, 2009 10:54 am
viletim! wrote
The best thing to do is pull modification out and throw it in the bin, where it belongs.

Build another pair of amplifiers from this circuit instead.


.           | +5v
.           |
.           |
.video   | / c 
.in   ---|<
.        | \ e
.      NPN  |   27   video
.           +--RRR--- out


NPN transistor type isn't too important, you can probably just use the ones you've got. I usually choose the BC548.

Only two components, as you can see. It's far more suitable than the other garbage one. Pin 15 is chroma out, 16 is luma out, and this circuit is only good for the CXA1145.

I modded my SMS2 (alex kid) and had a problem with the screen flicking or blinking. When first powered up in Alex Kid everything is fine but when its in the demo thats when the problem starts, can anyone help ?
Im using a pal SMS2 on a plasma. Oh and it seems to work better in 60hz mode and gets worse in 50hz mode. Do I need to remove the rf box ?
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Post Posted: Wed Apr 22, 2009 1:44 pm
My composite output modded SMS2 has a strange output on my plasma at 60hz also. I have taken the RF box out, so I don't think that is the issue. I'll have to look into this further.
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Post Posted: Thu Apr 23, 2009 6:41 am
Dano wrote

I modded my SMS2 (alex kid) and had a problem with the screen flicking or blinking. When first powered up in Alex Kid everything is fine but when its in the demo thats when the problem starts, can anyone help ?
Im using a pal SMS2 on a plasma. Oh and it seems to work better in 60hz mode and gets worse in 50hz mode. Do I need to remove the rf box ?


Does the screen seem to flash green and pink? Have the colours gone completely wrong and stuck that way?
If you have Sonic The Hedgehog, try that out.
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Post Posted: Thu Apr 23, 2009 8:40 am
Yes its doing excactly what you are saying even with sonic its the same, Ive tested on 3 different T.V sets (plasma, Rear projection & old 68 T.V) and all do the same thing.
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Post Posted: Thu Apr 23, 2009 11:26 am
Is it particularly bad with sonic? If it is, I've seen this problem before. Unfortunately I'm not sure what exactly the problem is.
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Post Posted: Thu Apr 23, 2009 11:41 am
no its the same with Alex Kid, it all looks good when I 1st start the console but when it goes to demo mode and also when playing the game its all up the creek.
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Post Posted: Thu Apr 23, 2009 2:06 pm
What about a game that isn't predominantly blue?
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Post Posted: Sat Apr 25, 2009 4:09 am
Ok ive tested a few games -

Alex Kidd - Flickers in demo and when playing the game
The Ninja - Flickers in demo and when playing the game
Mortal Kombat - Flickers in one of the title screens
Sonic 1 - Flickers in demo and when playing the game
Alex Kidd - Flickers in one of the title screens
Hangon - Flickers in demo and when playing the game
Wonder boy - Works perfect
Star Wars - Works perfect
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Post Posted: Sat Apr 25, 2009 5:15 pm
Mach-X wrote
Wow, I dunno guys. I guess it's fun to hack your systems and all, but from the initial pics, it looks like the svideo did give a somewhat sharper image, but the colours look washed out. I ran into the same thing when I bought a combined cable for my ps1/gamecube it has both composite and svideo outputs. And while the svideo gives a sharper image on my LCD tv, the colours look bad. I think some 'blurriness' is necessary on old consoles to give richer colour, as they were designed for CRT SD tv's. I also visited a website where a guy did an svideo mod for his turbografx 16, and in the comparison shots between rf/composite/svideo, I do have to say that the composite ones looked best for colour, even if they are slightly blurred for Bomberman :P


GameCube can do 480p, and there's a Y'CbCr to VGA (RGB/HV) cable: http://gamechoiceclub.com/navigateProduct.asp?product_id=209

If you're in the US, then I guess that S-Video is a good choice for SDTVs, but if you want something better, I would recommend something like this for your HDTV:
http://shop.ebay.com/items/?_nkw=hdmi+scart+converter - Note that I've not tested this thing yet, so buy at your own risk.
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Post Posted: Tue May 26, 2009 8:08 am
hey guys, awesome thread with great information. a while ago i tried to do the genesis s video mod from the circut orginally posted as being crappy, now that i see its possible with a much easier 2 component board, i was wondering if you guys could help me. i bought the old transistors and resistors from digikey but i cant find any BC548 on there. if i order these two things will i be set?

http://www.talonix.com/shop/item.aspx?itemid=7879

http://www.talonix.com/shop/search.aspx?sortby=name&search=BC548&sfield=keywords

thanks again!
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Post Posted: Wed May 27, 2009 4:17 am
spshortman wrote
hey guys, awesome thread with great information. a while ago i tried to do the genesis s video mod from the circut orginally posted as being crappy, now that i see its possible with a much easier 2 component board, i was wondering if you guys could help me. i bought the old transistors and resistors from digikey but i cant find any BC548 on there. if i order these two things will i be set?

thanks again!


Americans should use a 2N3904 transistor. BC/BD transistors are mostly used in Europe.
 
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Post Posted: Wed May 27, 2009 9:11 am
thanks for the tip viletim, i was able to do the genesis 1 stereo composite mod easily, but the s video stuff proved to be more confusing for me. im gonna give it another go thanks to your simpler circuit. im gonna order some new parts, if i get it to work ill post some pics!!! thanks again!

edit- can anyone tell me if the resistor i posted would work properly? i cant find any 27 ohms on digikey but the talon website has the 2N3904 and those resistors i posted, i just want to make sure before i order them. thank you very much
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Post Posted: Wed May 27, 2009 9:35 am
They're a little chunky being 1 watt rather than 1/4 watt.. but in terms of suitability it makes no difference at all.
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Any updates?
Post Posted: Mon Jul 27, 2009 5:14 am
Hello, this is a great mod for s-video but I also have faint vertical lines for my NTSC 27" Sharp CRT TV.

I used 27ohm 1/2 watt resistors and 2SC3311 NPN transistors and the colors are great but find in vertical bars in the luminance on all games (like the others are complaining about). Any way to use a capacitor or something to smooth out the bars. Thanks!
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Post Posted: Tue Aug 11, 2009 4:26 am
Just an update for all.

I rebuilt the circuit on a bread board using 2SC3311A's (first time was all soldered and heatshrinked), this time with some 1k Ohm trimmer potentiometers from radioshack (PN#271-0342 or 271-342 (same thing except packaging)).

Adjusting the trimmer on the chroma (C) to 485 ohm looks great, the very slightest hint if you look intensely now on Sonic 2. Now adjusting Luminance (Y) down to 6 ohms makes the picture brighter but I'm leaving it at 27ohms on Y for great clarity of the picture. As for color, its not affected and all colors look great still.

Using the Trimmer, for the RS 1K ohm I tied legs 1 and 2 together and used it as video out to the S-Video Jack, and leg 3 ties to the NPN transistor as described by viletim! If anyone uses the 2SC3311A NPN transistor, looking at the part number on front of the Transistor pinout goes. Emitter | Collector | Base (this is still the same as the 3904, just easier for me to acquire )

I must say thanks viletim! great mod!

So far I've played Comix Zone/Sonic 1/ Sonic 2/ Robocop Vs. Terminator and picture is super sharp and vibrant.


I'm using a 27" Sharp CRT TV/ NTSC (USA) Model 2 Genesis w/ CXA1145m IC

Hopefully this can help others with the Jailbar effect.
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Post Posted: Wed Sep 02, 2009 9:49 pm
Hello SMS Power. First time poster here. I was wondering if anyone could help me.

I've been thinking of doing the S-Video mod on my Sega. I have a genesis model 1 (the one with the frontal headphone jack). While searching the web I found a circuit in a page called "Sega Genesis Hardware Mods" and later found this thread discussion with a simpler design (but apparently meant for Master Systems).

Which circuit should I use? Thank you for your attention.


viletim! wrote
The best thing to do is pull modification out and throw it in the bin, where it belongs.

Build another pair of amplifiers from this circuit instead.


.           | +5v
.           |
.           |
.video   | / c 
.in   ---|<
.        | \ e
.      NPN  |   27   video
.           +--RRR--- out


NPN transistor type isn't too important, you can probably just use the ones you've got. I usually choose the BC548.

Only two components, as you can see. It's far more suitable than the other garbage one. Pin 15 is chroma out, 16 is luma out, and this circuit is only good for the CXA1145.
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Post Posted: Thu Sep 03, 2009 2:01 am
Use the simpler one. It's designed for any system using the CXA1145p and its variants, including the one found in most Mega Drive systems.
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