When I switch the TV on it just makes a continual clicking sound but never actually comes on.

it may have an internal shout somewhere causing the speaker protection relays to kick out..

the motor break assembly is going bad, if not replaced soon it will quickly draw down your batteries. [email protected]

could be just a few bad capacitors on the power supply, if you want you can do a visual of the power board caps will appear swollen on top and are easy to solder in cost about $1 each
value is 1000mf at 16volts usually replace four of them

I’m happy to help further over the phone at https://www.6ya.com/expert/eric_ab7c09ec01841771

probably a power supply problem,modern tvs use switching power supplies. these power supplies sometimes fail after a long period of use due to the constant charging and discharging of the capacitors

replace CP150 and CP114 you can get them at the following link they also have the ITC222 service manual which is listed under Thomson as Thomson makes your TV for RCA. The Capacitors are listed under the RCA parts and they do send instructions with pictures of where the capacitors are located as well as how to remove the board.
http://servicemanuals.vstore.ca/

I had the same problem with my tv, same make and model. I first continuously turn on and off my tv manually until I could get some kind of picture. This procedure took maybe five minutes. I was able to get a fine picture and sound, as if it was brand new! Other things to keep in mind, try to eliminate dust build up as much as possible.. Hope this helps out...

The clicking noise is caused by the relays on the power supply board trying to power up the system. Your TV has detected a problem that's causing the power supply to shutdown. Someone knowledgeable in electronics can track down the problem. The SOURCE of the problem could be another board other the power supply.

Clicking sound is power relay engaging. If all systems are not functioning properly, unit will shut down to prevent further damage and/or fire hazard

I noticed you wanted to chat at one point actually my first chance and sorry you had to go. Does this tv make any clicks when the power button is pressed?