S-Video Modded TG-16 not syncing - Anyone want to help me take a stab at this?

[Lastcallhall]

Yep! Just tell me what to measure!

[Jorge Nuno]

The CSync DC and AC voltage against GND

Also read my previous edit please.

[Lastcallhall]

OK.

Ohh so you do have a CSync source onboard. This makes things easier :P Do you have a multimeter and 2 resistors around the thousands of Ohms?

I never looked into this system so I'm gonna ask some simple questions:

Where does it's video come from? Is it directly from the VDP? Does it work fine?

The RGB and sync signals come from the C6260, and are mixed along the way to a standard RF out. If you use a turbobooster, you can connect that to the TG-16 for composite out and stereo sound. Last I checked, it worked fine (I removed the RF box to make way for the other connections, and I also verified it worked with the turbobooster). I'll measure those values now and get back with you in a bit. Thanks!

[Lastcallhall]

I get 4.5v across on DC Voltage. I couldn't measure AC - my meter starts at 200VAC so it didn't register. I can take it to class tomorrow and get a reading if you need it.

[Jorge Nuno]

So the RGB is encoded into CVideo using discrete stuff, or does it has an encoder IC?

Ok, that value looks correct for a negative sync pulse: Now grab a 10-12K resistor and a 680-1K Ohm one :P

[Lastcallhall]

It's discrete encoding - there's not an actual IC that I can see that generates the video signal.

Resistors found and ready.

[Jorge Nuno]

Connect them in series and wire them like this:

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

LOL @ ASCII schematic :V

Take care, I edited this message like 4 times

[Lastcallhall]

No worries, I will try this shortly - I have to get my son ready for bed then I'll have time to get this wired up. :O) Thanks for your help!

[Lastcallhall]

no dice. 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. So now I'm thinking it's not the chip (or at least that's not the only cause).

[Jorge Nuno]

And the circuit?

[Lastcallhall]

Nothing from the circuit either.

[Chilly Willy]

My suggestion is to take the circuit as you have it, and sketch out the circuit AS YOU MADE IT (verifying with a VOM as needed). Then go back and compare it to what you were trying to make. I'm willing to bet you have something connected wrong. Making boards like this can be just like programming - you don't see the error because you are comparing it to how you THINK you put it together rather than how you ACTUALLY put it together. Programmers do that all the time - reading the code the way they MEANT to write it rather than how it's actually typed in.

[TmEE]

I do exact same thing... I just draw out rthe schematic of what I created and then check it against original. I am always finding some swapped wire or component value

[Jorge Nuno]

If you have access to a scope, it would be great to see some pictures of the sync signal at various points

[Lastcallhall]

If you have access to a scope, it would be great to see some pictures of the sync signal at various points

I'll take it to class tonight and see if my instructor and I can't get some pics snapped of the signal. That said, I'm ready to tear it apart and start over again - the CXA1645 I bought came used from a supplier in Hong Kong, so part of me suspects the chip is damaged somehow. There's a supplier here in the US that sells them, but they're 15 bucks each, so while that's a possibility, it's also factoring into my cost vs profit situation. I don't want to sell a unit that cost me 125.00 in parts and repair for 100 bucks, you know?

Anyway, I'll see what I can find on the o-scope tonight.