The 55" TV that I repaired by replacing a couple of dozen bad electrolytic capacitors failed again about 4 months ago, after working for more than a year. I first described the repair
here and
here.
Last time it was used, it turned itself off after displaying a message about possibly overheating due to restrictive airflow. So, I unplugged it, and it has been sitting since. We do not watch much TV, and even the smaller 32" set in our bedroom has not been turned on for several months. But lacking of things to do inside the home as I try to stay out of the heat, I pulled it out trying to see whether I should fix it or to throw it away.
Now, the thing would not turn on.
When plugged in, this set will go through a boot procedure, not unlike a PC booting. It takes about 1 min, and a green LED on the front panel flashes during the procedure. After the light blinked about 11 times, the internal processor apparently crashed, and the LED turned off. After a second or two, the process started all over again.
Suspecting a power supply problem, I put a voltmeter on the main 15V rail, and watched it sagged right about the time the boot was aborted. How in the world am I going to isolate the culprit component among the thousand parts in this TV?
To make the story shorter, it suffices to say that researching the Web led me to a tiny 10uF capacitor that sits on the Vcc pin of the main switching regulator IC. What happened was that when the processor powered up the main signal boards during the boot process, the power demand surged, and the weak capacitor prevented the regulator IC from doing its job to increase the power to keep up with the demand. The voltage sagged, causing the processor to crash. The whole thing repeated every 10 seconds.
So, after removing the board, unsoldering the 10uF bad cap and seeing that its value being now only 2uF as measured with a capacitance meter, I replaced it with a new one. The thing is working like new now.
See photo of the set sitting on a pair of work stands. This time, I only had to take out the power supply, and not the more gory processor boards and their zillions of interconnect cables.