Home Theater Questions? Ask a Technician for Answers ASAP
To accommodate the HD upgrade there will be a realignment of Nine Network channel numbers. 9HD will be available through Channel 90, while the SD broadcast will be on Channel 91 (and 9).Read more at http://www.9news.com.au/entertainment/2015/10/28/22/50/nine-to-launch-new-lifestyle-channel-and-broadcast-in-hd#uIiWwOiyZf6IhZ48.99
That may be the reason you lose your picture...Your TV stopped processing SD - standard definition signal.
You should try channel 90 to see if that works, then try 9 and 91 to see if the picture disappears. If it does, then that TV stopped processing the older SD signal. Yet you lose the tuner SD while your disc player uses SD via the RCA cables. I think your TV's formatter from the tuner has failed.
That makes sense now.