Where can I tap a sync signal for s-video?

[thesteve]

you really want the grounds tied as close to the chip as possible, as you can see in this pic i have them jumpered across the chip.


BTW that chip outputs composite and S-Video

[lastcallhall]

No raster signal when the output is applied directly to the composite out - it still flickers.

I even pulled the video signal from A23 on the EXP port and fed it straight to the composite out - no change.

[thesteve]

i just pulled S-vid strait off the huc6260.
i needed to amp the Y output and filter C out of composite

[grahf]

No raster signal when the output is applied directly to the composite out - it still flickers.

I even pulled the video signal from A23 on the EXP port and fed it straight to the composite out - no change.

lastcallhall, your descriptions of what you have going to each pin looks good. I compared it with the CXA1645 datasheet, and everything is right. The only possibility is that one of your chips is fried, which isn't that likely, or you mixed up a wire somewhere.
You said you were getting composite video signal off of pin A23 on the expansion port. That's the wrong pin. Composite video is on pin A22. See this for the pinout:
http://www.gamesx.com/misctech/pcebp.php

[thesteve]

ya could go simple, and just pull S-Video right off the huc6260

the cap is 0.001uf
the transistor i tested with is an S9013
40 is pin 40 of the huc6260
comp is anywhere you can get composite video (I tapped the vid pin on the RF modulator)

[lastcallhall]

No raster signal when the output is applied directly to the composite out - it still flickers.

I even pulled the video signal from A23 on the EXP port and fed it straight to the composite out - no change.

lastcallhall, your descriptions of what you have going to each pin looks good. I compared it with the CXA1645 datasheet, and everything is right. The only possibility is that one of your chips is fried, which isn't that likely, or you mixed up a wire somewhere.
You said you were getting composite video signal off of pin A23 on the expansion port. That's the wrong pin. Composite video is on pin A22. See this for the pinout:
http://www.gamesx.com/misctech/pcebp.php

Oh, crap.

Someone on the Sega-16 forums said that something was probably overlooked. I'm tapping into the wrong signal from the EXP port...

I'll play with it now and see what I can do.

[lastcallhall]

OK, it still doesn't work, but I have it narrowed down to the chip...

From another member on Sega-16, I constructed this circuit prior to running the composite signal into the LM1881:

Connect them in series and wire them like this:

Code: [Select]

Gnd --|===|--#--|===|--- CSync
       680   |   10k
             |
             |---||---» LM1881 CVideo input
                .1uF

LOL @ ASCII schematic :V

Take care, I edited this message like 4 times :p

[/FONT]

I purposely left the leg on the 10k resistor connected to composite uncut and when I connected it directly to the composite out, it stabilizes the picture, but the colors are all out of wack. I tried to take a picture and video, but it doesn't come out the way I see it in person. Anyway, I'm fairly sure that the CXA chip is the culprit, as I can get a solid sync signal from the EXP port, the C6260, and from the composite out on the EXP port, as well. So, what I'm going to do is I'm going to order a new CXA1645 from a stateside dealer and just redo the entire circuit. This may take some time, so I'll check back in once I get that done.

[thesteve]

skip it, you dont need an encoder, as the TG16 outputs S-Vid almost native.
you will need a driver amp for the Y (luminance) and an isolation cap for the C (chroma)
see simple schematic above

[lastcallhall]

What the hell, I'll give it a shot.

[ApolloBoy]

What the hell, I'll give it a shot.

Let me know how it goes, I'd love to give that mod a shot if it works!

[thesteve]

i just tested it before posting

[lastcallhall]

What the hell, I'll give it a shot.

Let me know how it goes, I'd love to give that mod a shot if it works!

Will do. Looks like I'm going to have to order the S9013 - All I have are 2SC945 and 2N3904 transistors lying around (unless one of those will work, but I'm guessing not).

Off to Digikey...

Also, @ TheSteve: which pin did you tap into on the RF modulator for video? I took my modulator off to make room for the other mods. Thanks!

[ApolloBoy]

Looks like I'm going to have to order the S9013 - All I have are 2SC945 and 2N3904 transistors lying around (unless one of those will work, but I'm guessing not).

You could try a 2N3904, it's an NPN transistor like the S9013 is and it usually comes up as an S9013 substitute.

[thesteve]

any npn should work fine
rf mod pin2

[lastcallhall]

You could try a 2N3904, it's an NPN transistor like the S9013 is and it usually comes up as an S9013 substitute.

any npn should work fine
rf mod pin2

You're both awesome.

It works! None of that fancy encoder stuff, you can pull it right off of the chip! As soon as I find my video capture card, I'll toss up some comparison pics. However, I can't tell if the chroma signal looks slightly washed out, or if that's just the way the games are meant to be seen. Either way, I'm sure there's a method to adjust it.

Thank you all so much!