Maintenance Hisense LCD TV TLM2619 boot without backlight, with sound, apparently high voltage board or 24V power supply problem.
Open the cover, observe and measure, and soon found that the power supply board does not have 24V output, remove the power supply board for separate maintenance, and found that the power supply board's 24V power supply block W5667's absorption circuit in the absorption circuit CE023 2N2 burned, haha, saving money Just find a 1N8 and turn it on. The measured 24V voltage output swings around 10V, and occasionally reaches 24V, but there is no load capacity.
At 10V or so, the voltage regulator optocoupler is measured. The voltage of the 2 pin is almost no. It indicates that the fault should be on the W5667 circuit. The components are checked on the line. There is no abnormality. Only the W5667 can be suspected to be damaged.
Purchased two W5667, replaced, the fault remains, you can rule out the reason for W5667.
Now only careful and comprehensive inspection, the PFC measured at fault is 379V, is normal, W6667 power supply 6 feet is 13V, is not normal, 7 feet for 0.05V swing is not normal, W5667 7 feet for voltage regulator 24V The higher the voltage, the lower the 24V. It is reasonable to say that the 24V voltage should be high now. In the occasional output of 24V, the voltage of the 7-pin is 1.2V, the maintenance is in a desperate situation, and the tester supplies 22V external power at 6 feet, and the fault remains.
Continue to check and repair, in order to facilitate the online replacement of components to remove the W5667 heat sink, changed to a small heat sink anyway, W5667 has no power output, and then turn on the live measurement, unexpectedly, W5667 has a burnt smell in the measurement, Is the test leads causing a short circuit in the measurement? With the suspicious removal of the W5667, I suddenly found that the small heat sink of the W5667 is very hot, haha, now I understand the cause of the fault. . .
The reason is very simple, the W5667 is overloaded, and the culprit of the overload is the 24V transformer. So I can't wait for the W5667 and the resistance of 0.33 ohms, boot, W5667 immediately burst, this time burned a lot of components, fill the burnt components, boot, 24V power restored to the original 10V no-load state, in order to verify the 24V transformer The fault, power on for five minutes, the transformer has a slightly hot temperature, the heat sink of the W5667 is hot. . .
The transformer is not a universal part and can only be re-wound for repair. . . .
After the machine returns to normal, the voltage of the 6 pin of the W5667 is 23V, and the voltage of the 7 pin is 1.57V. .
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