Boneless

Hi everyone, I have an Atari 2600 "Light Sixer" with a mysterious problem (see video below). Once turned on and configured with the correct video rate, the console emits interference and a beep but shows nothing (with or without cartridge). However it is definitely not the game as I tried it on another Atari and it works fine. I cleaned all the motherboard contacts, including the various chips (TIA, CPU and RIOT), I cleaned the cartridge reader pins and also the six switches, but the problem persists. I also tried to adjust the trimmer of the RF modulator but nothing changes, obviously I first checked with the multimeter if the RF cable had continuity and it works. What do you think could be the problem? Probably the RIOT damaged? Or the RF modulator? What could I check with the multimeter? Thanks! :] The video problem Front view without plastic shell Motherboard front view If you need more photos let me know:]