Turn on an hour and then turn off and you have to disconnect from the power to turn on again

check the power supply (if technical), possible false contacts (cold welds) or filters in poor condition.

test cooling the microprocessor with an external fan, if it does not turn off, adapt a fan, using a 12v swiching voltage.

Hello David, good afternoon, the sony are diagnosed by LED flashing sequence, when it goes off is the standby LED flashing? if it does not blink it is possible that the source is turning off, if so indicate me the code of the source plate I leave you the diagram https://elektrotanya.com/sony_kdl-32ex340_kdl-42ex440_kdl-42ex441_chassis_az3fk.pdf/download.html under the image of the diagram it says processing, in one minute it changes to get manual, there downloads successes