You have a husband problems, not a ss problem. Since your husband can not properly address it, you go tell the child to turn it down or off - his choice. 

Noting cutting the plug off of the end of the power cord won't fix.

Make sure to unplug it first.

TVs until they were preteens and we have always had a "volume" house rule. Five kids (four were teens at the same time) plus a variety of bonus kids (friends, kids who needed a place to stay for a few days, etc) and we were in desperate need of a volume rule lol! Make it a house rule and post it somewhere. If the kid breaks the house rule then you remove the TV from the room for X amount of time. If it continues then you remove it all together. I have never had to get to step two in 24 years of parenting. 

I post every rule. I have a white board in the hall with the calendar and the basic rules. We are down to one kid here full time and one almost adult who spends most of her time at my oldest daughter's as it is closer to school. The rules remain even though the kid at home doesn't need them and the adult kids still follow them when they are here. 

If you've given your husband an opportunity to fix the problem and he has chosen not to, fix it yourself. Next time the volume is turned up after SS is told to turn it down, march into his room and remove the tv. I don't consider that "punishing" SS; it's just facilitating a good night's sleep for you, an adult in the home. If your husband doesn't back you up, you have a significant problem with your marriage that will need to be addressed.

I don't know if this is possible in your house, but I can shut off all the sockets or lights in a room from the main fuse box ...

If normal sleep hours, kid need to turn it off. He needs sleep too.  If you go to bed early (say 6 PM), for whatever reason (shif work, etc, does not matter), kid needs to use headphones

If the kid's dad won't do anything, you take matters into your own hands. Is the TV too big to toss out of the window? That might get your husband's attention.

I was against the TV being on at bedtime before I met SO. The thing is the kids really are used to it. I personally don't agree with it but it's not worth the fight. However I do have say in how loud it is and I will take the TV cord if it's a problem. I'd focus on that. Good luck.

"scolds" you for taking away the precious TV from skid's room or gets another one then you KNOW you have a DuH problem.

You have a DH problem as he will not parent his children.

However, it is your house too and everyone needs sleep.  I, personally, would give one warning about leaving the volume low at night.  One.  Then, when he has the tv on too loud, I'd take it for a few nights.  After the third incident, I'd sell the tv/smash it/throw it out the window.

And make my "D"H sleep on the dang sofa until he decided that his wife is more important than his little pwecious and his cursed tv...

Change the Netflix password.

Take tv and put it in shed. 

I had a similiar problem when my DH would let YSS sleep in the living room. This kid was in the living room 24/7 when he came to our house. The TV would be on all night as well. I finally told DH that he needed to deal with it or I would. The kid even asked me to be more quiet when I was leaving for work one day because I woke him up. Nothing surprises with my DH's feral kids though. I don't put up with their crap. OP please do not let this kid run the roost of your household. Your DH needs to deal with this kid and if that doesn't work then take the TV out of the skid's room until he can learn to be respectful.