Interference on S-video when using third party Power. SMS

[Mamejay]

Hi guys,

I have been doing heaps of S-video mods for SMS's now but have come across a weird issue.
I have recently updated my S-video mod to use the circuit attached.
This works perfectly when using a decent power pack such as a genuine Sega one but when i use some cheap third party ones I get a lot of static on black screens.

Composite video works perfectly and my old mods that use the 220uf cap and 75ohm resistor never had this issue.

Composite still works fine its just S-video with the new circuit.
Is there way to clean the power up by creating some sort of a filter?

[ApolloBoy]

You might want to add the 220 uF caps to add some filtering. What are the specs of the power supplies you used?

[omp]

You might want to add the 220 uF caps to add some filtering. What are the specs of the power supplies you used?

+1 Are they transformer type or switchmode? Interested to know this myself, as I have also done the same amp for the S-video but never thought to try it with a newer switchmode power supplies that I use.

Edit Also are you selling these on ebay? Ebay Australia has a had a big crack down on any modified consoles sold on their site. If you are just modifying for AV and S-video you would be ok, but anything further and they will pull it.

[Mamejay]

I am using 9V 1Amp Power supplies.
http://cgi.ebay.com.au/ws/eBayISAPI....m=190464937136
When you say add the 22uF cap, where would I put this?

[omp]

I believe it would be the same as you would on the old circuit, inline.

Also that power supply you have indicated is ass about, negative needs to be centre, positive outside. That power supply may not be a regulated type, which may cause issues if it is not a "smooth" DC output.

Good find on a cheap power supply though, I thought I was doing well on the ones I get, $10AU 9VDC 1.3amp regulated.

[Mamejay]

Thanks for that OMP.
I know about the polarity and of course I have reversed it.
So for the inline would I use a 220uf cap 1 each for luma and Chroma before the circuit or at the output? Also what would be the polarity for the cap? Negative pointing to luma and chroma out?