Sega Genesis Model 1 S-Video Mod Problem

[AlphaDangerDen]

This may be off topic, but does anybody have experience with recapping VA2 HDG Model 1 systems? If so, how effective is it at reducing or eliminating the rainbow banding?

[evildragon]

To be honest, it's not really going to reduce rainbow banding.. They did this when new. It's just how it is.

Now go RGB and you won't have to deal with it.

[MaxWar]

Well recapping my VA3 did help with the rainbow banding.

[evildragon]

Huh, didn't for me.. That's one of the few times I could safely say it didn't..

And I have a VA3 also.

[t0nito]

I think the rainbow banding dissapears if you replace it's internal clock to the video decoder with a crystal oscillator, I've done the 60Hz mod on my PAL Megadrive and used a 3.58 MHz crystal and I can't see any banding on composite NTSC mode or jailbars when using RGB.

[DemVil12]

PAL MDs uses a bit different video curcuitry also... DL lines and such... Just because PAL is a more strictly standart, and requres a more complex curcuitry ( yes, in reference variants ).
That's explains why PAL units ( especially MD2s ), often have a noticeably better video quality in standard NTSC 3/58 than native - NTSC variants...

And a little advice, or "how i get rid of rainbow banding on a CXA1645 NTSC MD2s"
Connect a 28pf ceramic capacitor and a 68uH unductor in series between leg 17 and a GND point.
Personally i used a 22pf cap, as i haven't found a 28pf variant.
Or you can use a 8-30pf or any other variable capacitor.
After this, rainbow banding on a VA4 NTSC MD2 was ~3x time less than before ( yes it's still there but not as harsh a it was )

Also, Ace mentioned that external 3.58 mhz crystal do reduces awful edge pixellation on most ( if not any ) NTSC MD2's.

[douglie007]

Bring up this topic again, I have an issue with a wavy lines on after the Svideo mod, I removed my RF and the Serial ports, I took the 5v from the pin that the RF left and used the side for grounding, would on of them cause the issue I am seeing? and

[Xalphenos]

Bring up this topic again, I have an issue with a wavy lines on after the Svideo mod, I removed my RF and the Serial ports, I took the 5v from the pin that the RF left and used the side for grounding, would on of them cause the issue I am seeing?

I have had exactly this happen under the same circumstances. Removed RF modulator, drew +5v from where the Modulator was and this happened. Moving the wire to a different +5v source fixed it. I'm not sure why; I never investigated further. I had no problem drawing +5v from the same spot when the modulator was still in.

[goombakid]

I usually take +5V from the 7805 voltage regulator itself (rightmost leg). You can also try using a NTE85 instead of a 2N3904 as your luma transistor.

[graffias79]

If it helps, I recently did a successful S-Video mod to my Genesis model 1 with a CXA1145 chip. Here is what I did:

I took pin 15 from the CXA1145 chip into the base of a Radio Shack 2N4401 transistor, the collector to pin 19 to gather +5v and the emitter into an NTE 75 ohm resistor then into the S-Video jack.

I took pin 16 from the CXA1145 chip into the positive side of a Radio Shack radial 220uF electrolytic capacitor, then the negative side to an NTE 27 ohm resistor then into the S-Video jack.

I pulled ground from the edge of the motherboard.

I got the nice S-Video jack from Console 5.

Beautiful sharp clear image.

[douglie007]

Ill try moving the power first, and if it still doesn't ill try a different transistor

[douglie007]

so the power was the issue, I moved it and the pic is awesome, I checked with my meter and I was getting 4.85v from the RF port, and 4.92v off the 7805, but that wouldnt make the wavy look. I wonder if the voltage is carrying some signal on that line that would make for a poor pic.

[Xalphenos]

Glad that worked for you. Perhaps putting a capacitor on that line would solve the problem. It did work fine from the exact same spot while the RF modulator was still there for me.

[douglie007]

A few years later, I'm trying to get the svideo off the va7 board. And I'm getting nothing. Is the video chip different on the va7?