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View topic - Quick and dirty S-video mod for PAL SC-3000

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  • Joined: 31 Oct 2007
  • Posts: 835
  • Location: Estonia, Rapla city
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Quick and dirty S-video mod for PAL SC-3000
Post Posted: Fri Jun 14, 2013 6:18 am
What you need :

*some wire
*soldering skill
*25...33ohm resistor
*one 2SC945 or equivalent transistor (optional).

On the modulator board you have to disconnect J107. This makes the Composhit output become chroma alone.

For luma you have 2 options :
1) Solder wire with series resistor on the blue wire from VDP to your connector.
2) Have a source follower on the blue wire first. Blue to base of the transistor, collector to +5V and emitter to the resistor and that to your connector.

Drawback here is that there is no more composhit output, so RF modulator will be ineffective.
I used custom pinout on the AV out connector so I can reuse my general purpose AV cable.
SC3000-jumper.jpg (343.08 KB)
SC3000-jumper.jpg
SC3000-Svid.jpg (293.48 KB)
SC3000-Svid.jpg

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  • Joined: 05 Jun 2010
  • Posts: 693
  • Location: Pennsylvania, USA
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Post Posted: Sun Jun 16, 2013 1:28 am
Cool stuff, but I see a trace completely missing in the first picture. :S

Also, where did you get the Luma from? I don't have one of these myself, but someone else will probably want a more idiot-proof guide.
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  • Joined: 31 Oct 2007
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  • Location: Estonia, Rapla city
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Post Posted: Sun Jun 16, 2013 8:56 am
That ripped trace is unrelated, and result of whoever repaired this thing before I got it.

Luma is grabbed from the Y output pin of the TMS and then buffered.
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Post Posted: Sun Jun 16, 2013 5:23 pm
Just like the other S-Video mods out there, using any generic NPN and a ~33ohm resistor (give or take some to adjust for your brightness taste)?
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  • Joined: 03 Oct 2011
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  • Location: New Zealand
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Post Posted: Sun Jun 16, 2013 6:02 pm
Very cool :) Nice job.

I'll give that a try and see how it compares to the Component Video output mod I've been working on and the Yeno SC-3000 RGB output (which is kind of the gold standard so far).

If the value of the resistor is up to personal taste (and if you need different boost levels for different TVs), then I would suggest sticking a 25K Ohm resistor in series with a 10K Ohm trimpot or similar to make it easy to adjust brightness, but giving you a minimum value that you can't go below. Or maybe a 20KOhm resistor in series with a 20K Ohm trimpot. Something like that anyway.

Note - I still need to try replacing the capacitors on the 4095 daughterboard on one of my SC-3000s to see if that fixes the colour fade / washed out red problem. (You mentioned that in an earlier thread). I assume that will also be required to get good output from this mod.

Cheers
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  • Joined: 31 Oct 2007
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  • Location: Estonia, Rapla city
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Post Posted: Sun Jun 16, 2013 6:52 pm
The resistor is in ohms not Kohms :P

I used 33ohm resistor, it gave me nice enough image. 25 would have brighter image which some people may like. 47 and higher will have too dark image.
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  • Joined: 03 Oct 2011
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Post Posted: Sun Jun 16, 2013 9:19 pm
TmEE wrote
The resistor is in ohms not Kohms :P


Oops. Sorry, my youngest daughter has been getting up at 5am every day and I've been getting up with her. I obviously wasn't at my sharpest when I read that. :)
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