What is the cable going into the back of my tube?

Hi, I'm trying to remove the back of my Philips 36pt71b so I can inspect the boards and take it to a shop. There is a cable going into the c=back of the tube near the top. Where it enters there is a rubber grommet that appears to be there to keep the duct out. There is some sort of metallic thing at the end where it enters and this can be turned with a scraping sound. However it does not want to easily pull out. I can't remove the back of the tv without disconnecting this cord so am asking for help. Thanks!