CXA2075 Problem with Scrambled Output

Hi everyone. I've been reading the forums for a long time, but have really only posted once or twice.

i searched for an answer to this on several different forums, but i haven't seen a resolution.

i am making the basic NTSC application circuit from the datasheet to use for arcade boards. but for some reason the Composite and S-video output is garbled, in a way that looks like a sync issue to me.

• I put an LM1881 on the sync line, but it doesn't change anything.
• I moved onto the Y-Trap, and it doesn't make any difference if i have the 3.32k resistor on it or not, it doesn't change the image, so...
• I thought maybe this was a bad chip, so i swapped it for another new one, but no change.
• I swapped the 3.58 oscillator, no change.
• i've tried pots on the RGB lines and it makes no difference to the garbled part of the image, just changes the colors slightly.

The weird thing is that when the input image fades in or out, the picture looks totally fine. that's what led me to look at the Y-Trap.

has anyone got this circuit to work? Has anyone had this problem and resolved it? Thanks

S-video Pics:
http://imgur.com/8UTHM6P
http://imgur.com/FKEbAn1

when the screen fades:
http://imgur.com/X1g1kCK

 

Do you get this problem when using RGB SCART/JP-21 cables with a compatible converter/TV?

 

Not sure what you mean. I am taking the RGBS output from the arcade JAMMA connector into the chip with the appropriate 0.1uf caps on the RGB lines. The output is through an SVideo connector, and a Composite RCA connector. Composite, Luma, and Chroma all have 75ohm resistors and 220uf polarized caps as per the datasheet.

edit: composite actually has two resistors of different values instead of the 75ohm.

 

I meant take the RGBS output and connect it directly to an XRGB mini via RGB JP-21 cables or to a generic RGB SCART to Component/HDMI converter via RGB SCART cables. This is MUCH better quality than composite video/S-Video.

 

I do not have an xrgb mini. I already have component video working with another chip, this is for me to use additional output types as needed. I could use some help with the problems i'm having.

Edit: i am aware of jrok and neobitz boards. I am trying to make the same thing for myself, which is a lot cheaper and more fun.

 

The voltage level on the R, G and B lines are too high. It has to be around 1vpp.

 

Thanks so much for the reply i sent you a PM asking for a little guidance on this.

 

So the solution was extremely simple. Oliveira suggested i just drop the voltage with a simple voltage divider. I just mimicked the resistor values that worked on my component chip, and voila, svideo and composite video now look perfect!

i used two 1k resistors on each R G B input line.

thanks a million for the solution Oliveira!

Pics:
http://imgur.com/UQQLqJU
http://imgur.com/IDXP78h