Facing TV Problems? Ask a TV Technician.
Hello, Sorry you're having problems. I will address what you've asked in order here:
1) Offhand these symptoms (the TV not showing a power light at all, and then the set tuning ON, but with no control at all over the Volume to turn it down) directly points to a faulty/failing Mainboard in the TV. The Mainboard contains the EEPROM (processor) that controls the turn on/off function, as well as processes ALL volume, and the remote commands.
2) It is indeed fixable, but requires replacement of the Mainboard. This is roughly a $100 part on the used/pulled market (new parts are almost non-existent as all are pulled from sets with broken screens). Or closer to $250 parts and labor to have a TV repair shop perform the repair.
3) It is ONLY worth repairing if you are a DIY type and comfortable removing the back of the TV and replacing the Mainboard yourself. To help in this decision, the board is "plug and play" (meaning no soldering or special tools are needed to replace it). However if this is not something you're comfortable with, given the cost at a shop it does not make sense to put $250 into this set since it can be replaced for just a few more dollars.
Is this something that you were looking to repair yourself? If so, let me know and I will search for the Mainboard for you.
I just checked and that board is showing as "out of stock" at the link below (as well as other online vendors):
That said, it may make more sense to put that same money towards replacement of the set unfortunately, or keep searching to see if a site eventually has one in stock.
Other than that I'm sorry for the bad news here and wish there were a quick fix.
Let me know if you need further help. Also, please do click a 3-5 STAR rating for my efforts before you go. That is how I am credited for my efforts by the site.
Do you need further assistance with this please?