Sony cxa1645m trouble

[unstablewarpfield]

Hey all.
I've been experimenting a bit with a console that uses a sony cxa1645m.

According to the datasheet a 220uF cap and a 75 ohms resistor is required on the rgb lines. The thing is... i get no image on my test tv as well as my main gaming tv through a framemeister. (Once I saw a little bit of an image fading to black)

When I scope out my signals I get a clear csync signal. My test tv recognizes it as ntsc, so sync is fine. The rgb lines however display no signal on my scope, except for when I boot up the console. They fade away within a second or two.

When I measure voltages on rgb, straight from the chip I get 0.6V on either r, g or b which sounds good to me. After the 75 ohms resistor I also get .6V, but as soon as I measure after the 220 uF capacitors I get absolutely nothing. 0V. I tried checking up on the caps, tried measuring them, swapping them... did everything. Why is this happening? Anyone has any idea?

[Syntax]

Fading to black would indicate your cable has no ground.

Your amp sounds fine, using a multimeter there should be 0v on the other side of the cap.

[unstablewarpfield]

Thanks for the reply. Upon further investigation I found signals on all lines up until I plugged in my scart connector. Wobbling it around and plugging it halfway got me an output again on my scope. I think in some way my scart head got damaged. Soldering up a new cable and will see if that helps

[unstablewarpfield]

Hmm... I rebuild a scart cable from scratch. Individually shielded... metal scart head... gold plated... everything... still I see it fading to black in a second or so through my framemeister. Other tv without framemeister is showing "ntsc" but no image... it's weird to me because I have everything hooked up as de 1645m datasheet dictates...

[Ryoandr]

What is the console ? Cause on like MD or Saturn, you can't use the sync pin as is, you need a capacitor and a resistor. PAL Saturn also has 12v on the pin instead !

If the console doesn't have a sync pin, like Playstation, you can use composite or luma as sync (I think they already have the components needed inside).

[unstablewarpfield]

Yes... sync I pulled down to 75 ohms level with a 470ohms resistor and a cap. To be honost... sync is about the only thing that checks out on my scope. I tapped into the legs of the ic directly for rgb (sending it to an 8 pin mini din) because the stock console only outputs composite.

[Syntax]

Connect all grounds and the shield in the scart head.

[unstablewarpfield]

Connect all grounds and the shield in the scart head.

Check! I confirmed the cable works on another console with no problems. Image and sound.
I also reconfirmed that the console works on it's composite output. Working fine.

Still the console is only showing me a flash second of screen before fading to black. I also see this on my scope. I get a signal on r, g or b, which quickly falls to nothing when I connect the scart head. Pretty puzzled about this one...

[unstablewarpfield]

Solved!!

I was using "csync in" from the1645m as my sync signal. Without sync connected I had 3 clear rgb signals on my scope. With that sync connected I had nothing but sync on scope.

I used composite video out from the chip qnd it works now. I'll have to add an lm1881 to my mod but I guess my Casio Loopy is going rgb soon