Harsh S's in sound using satellite box - CTC-5

[frenchy]

If it was the set's fault, I wonder why it wouldn't do it on every satellite channel, or on antenna or other sources either. Even seems to vary by the content of a given channel (show vs. commercials etc.)
I've tried tweaking the AGC, the 'sound reject', and the fine tuning, none had any effect on the scratchy, loud S's.
Today I also tried unplugging one of the L/R channels (since it sends stereo from the sat box to the RCA/rf box)... noticeable reduction in volume, but no real difference in the harshness on the channels that are doing it.

Would be cool if I could wire up an RCA socket to the right place in the speaker amp section so that the RCA sound output from the sat. box went directly to there, so that tuning and RF could be taken out of the equation if I wanted... but I would be worried about the chassis being 'hot' and all the high voltages. Would there be a safe place to attach an RCA socket for this, and where the volume control on the set would still work?