Hi guys,
I made a simple video circuit that I prototyped externally, like a mod board - to install in older consoles and improve RGBs video output. I have this board specifically attenuated now to one console.
The issue with my protoype was the green channel wasn't balanced with red and blue. They should all be totally equal outputs. Green seemed to have a mind of its own while red and blue were perfectly balanced. Tested using a full white screen to saturate screen with maximum R/G/B levels.
I ignored the issues with the protoype and made a PCB - I've now put 2 together and I am having an issue now with the BLUE output being stronger than red and green!
The R/G/B signals are all attenuated with the exact same components
5v: [5k6 pullup] ----> [R/G/B SIGNALS FROM CONSOLE] ---> [2k ohm resistor] [to LT6557 input] --->1k3 pull down
Then signals are AC coupled into the LT6557 RGB input pins off the end of the 2k resistor.
I have checked with my scope and everything's balanced on the inputs, but the output is around .3-.4 VPP stronger on blue. (the issue on prototype was similar but with green)
I'm not sure what's going on here!
I have used 10nf capacitor on each power pin as per data sheet - but the main power line filter I used a 220uf as this is what I had on hand protoyping. I didn't really find a difference with or without the additional 10nf per power pin.
Any help would be much appreciated! this is driving me crazy - i have quadrouple checked my proto and my PCB
