Hello,
I have a Philips 25PS40 CRT TV from around year 2001, it only has 1 AV Composite input. Few days ago I took it apart (my first ever CRT TV disassembly) and I found that it uses a TDA9587H IC chip, not much inofrmation on internet about it, but on the IC I found that it has spare RGB lines and (C)hroma line!



I soldered RGB cables to pins 51,52,53 and S-video cable to pins 44 and 45.

The TV's circuit board is highly integrated, besides 2 ICs there's almost nothing there, not the easiest TV to work. Stuff like OSD and teletext features are right inside of the TDA9587H IC itself. I have spent last few days reading about other people's mods, from people hijacking OSD RGB signals to people injecting signal just before the CRT gun on the neck board, at this point I'm not keen on getting RGB input working since I don't have any device that can output RGB (but I'm planning to mod my Sega Genesis Model 2 soon to RGB), but I have been very interested in getting S-Video to work. So far I'm stumped as to
how signal should be
grounded or
filtered. I see recurring pattern of incoming signal getting
pulled to ground with 75 ohm resistor and then going
through 0.1uF ceramic cap before it reaches the Jungle IC. Like this:

Well I tried 80 ohm resistor (I don't have 75) and 104 ceramic cap, and this is what I get on my XBOX via S-Video:

When I disconnected the Chroma line image stops jiggling but of course goes to black white. When Chroma cable is connected the colors are very dim and seem to bleed at some points. When I run Chrome straight from my XBOX to the TV without any other components the TV partially shuts of (the Tube goes off but 5V electronics in TV seem to be still on, I have to power cycle the TV to get it back on).
So I'm asking eevblog folks for help, what is the science behind Chroma signal? How should the signal be handled before it reaches TV's video chip? How can I troubleshoot this issue with oscilloscope, what to look for? As a hobbyist I have never worked with NTSC signal so I don't know what to look for, but I have looked at Composite signal in the past and I was blown away, there's so much happening, I only have Tektronix 2225 scope and I'm not even sure how to set it up (the coupling, trigger, etc) for NTSC troubleshooting.
Thanks.