Skyworth LCD TV 32E55HM power failure repair example - Appliances

MOS power IC full range

Filter 18.432M

At 7 o'clock tonight, a customer drove a Skyworth LCD TV 32E55HM to repair, the model is as shown below. Power on the test machine, the red light is on, and it flashes. It cannot be started by remote control or by pressing the standby button. When the customer comes, he asks how much it costs to repair. I heard the lowest after the hearing: red and black, the customer still wants to counter-offer, I finally did not agree, or left the phone to let me fix it.
Uncovering detection: Power-on measurement power supply filter capacitor voltage is 350V, normal. (This model does not have a PFC circuit.) The power chip is TEA1733P. The voltage of the 1 pin is 20 V, and the 5 pin is only 2.3 V. I don't know if it is normal, and my heart is not at all. Re-measure the output voltage: 24V is only 15V; 12v is only 6V; 5VSB is only 3.5V, and it does not stop. The reason why the indicator light flashes is caused by the instability of the 5V voltage. This is obviously caused by the low output voltage and the boot can not start!
Because there is no drawing data, it is not easy to judge whether the power supply part or the main board is short-circuited. I had to unplug the connection to the motherboard and use the light bulb to make a judgment. Connect the 24V, 12V bulb load, and force the power on, the bulb is not red! I only heard the power supply part "beep". At this time, I have a few in my heart: the power chip may have a problem. Power off and let go of the power loss of the power supply filter capacitor, and deliberately remove the TEA1733P and replace it. Turn it on again, the light bulb is all on! Then the circuit is restored, and then the power is turned on, the indicator light does not flash, and then the green light is seen. At this point, the backlight is also on, only the sound of the splash screen is heard! On the signal line, the sound map is normal.
After repairing, I also downloaded the power supply drawing of this TV online, and shared it with everyone.

Skyworth 168P- P32EXM-00 power supply schematic.rar