Sony CRT KV-27FS12 has no video only on composite but has OSD and sound

[plantedcorpsemika]

I have a Sony KV-27FS12 that on all of the composite inputs (front and back of the tv) outputs no video, but outputs sound. The component inputs work perfectly fine though, but I haven't tested S video to see if that works either. I prefer to use composite inputs just so then I can have all my consoles hooked up to them. The component inputs on the board have been reflowed, so the input jacks don't have cold joints. Any help on how to fix this or at the very least where to look to troubleshoot this problem?

[KPackratt2k]

Does the RF input display static (or a picture if you have a device hooked up to it)? If not, then it's likely that the comb filter chip (IC302) has failed. Since I happen to have a spare salvaged from a damaged KV-13FM12 (which uses the same chip), I can send you a replacement if you're having trouble finding one, though it would be worth a shot to check any of the components in its circuit to make sure none of the supporting components (e.g. capacitors, resistors, and inductors) are bad before resorting to replacing the chip itself.

Otherwise, check to make sure the ESD protection zener diodes (D203 and D208) aren't shorted. If they are, replace them with 10V 500mW zener diodes.

[plantedcorpsemika]

No static when hooking up composite cables in. I guess I'll probe around voltages on IC302 to see if it's getting sufficient voltages and go from there. Will update eventually

[plantedcorpsemika]

Whoops, just realized you said RF and meant the coaxial cable, not the composite cables. I'll test that later when I get time

[plantedcorpsemika]

update: it was the comb ic, thanks !