Tv shuts itself off

Sharp smart tv shut down by itself after 5 minutes if it rest a long time. Then shut down after some seconds.

Tv used to shut down by itself after 30min when I bought it as used and i opened big holes on tv cover on behind. then the time delayed up to 3 hours.
But now it shut down after 2 seconds if tv rest 10 hours the time is initially 5 min then 1-5 seconds.
I changed 7 pieces capacitors but nothing changed. The power card number is HLL-4255WJ
And it has 12v and 16v output, 12v is always constant. On 16v output, there is 19v when tv standby, when the tv is working it drop to 17volt.
What is the problem? Sharp smart tv shut down by itself after 5 minutes if it rest a long time. Then shut down after some seconds. Tv used to shut down by itself after 30min when I bought it as used and i opened big holes on tv cover on behind. then the time delayed up to 3 hours. But now it shut down after 2 seconds if tv rest 10 hours the time is initially 5 min then 1-5 seconds. I changed 7 pieces capacitors but nothing changed. The power card number is HLL-4255WJ And it has 12v and 16v output, 12v is always constant. On 16v output, there is 19v when tv standby, when the tv is working it drop to 17volt. What is the problem?

Failing components especially aging capacitors becoming thermo sensative can cause this. You would need the proper setup and tools to service this. Failing components especially aging capacitors becoming thermo sensative can cause this. You would need the proper setup and tools to service this.