TPD.NT72563.PB771 Power Board Dead Reasons

This is a TCL L32S65 Power Supply Repair Guide. It does not have a 12-volt power supply. It uses PWM IC number LD5760 in its power supply section. The power supply of this set was also sometimes turned on. When this set came to me, it would turn on frequently. Such faults are confusing. I opened its back cover, turned it on, and put it on testing so that as soon as it turned off, I could get to the cause of the fault. This has been performing perfectly for quite a long time. I turned off the switch and turned it on again and realized the fault was that it wasn’t generating 12 volts. Next, we will show you step-by-step how this fault was diagnosed and what was done to resolve it.

Symptoms of the Fault

Its power supply section was covered with a MOSFET heat sink. First, I carefully separated it from the circuit board. Now below, I see its PWM IC LD5760. The main function of this IC is power management. It is called a green mode power-saving IC. It consists of 7 pins. I tested the voltage on its main VCC pin number 6. There were 5 volts here; this voltage was low. Every IC has a voltage threshold. If the voltage is less than this, it does not work. The voltage on its pin 6 comes from the primary winding of the chopper transformer; a 10-ohm resistor is placed in series, then it is converted to DC using a diode, and then through another three-pin diode, this voltage is applied to this pin. 

Main Causes of Failure

Now I had to investigate pin number 6 to find out why the voltage is low here. To trace the reason, I checked this pin with a multimeter by selecting the diode scale and found a leakage reading at this location. This means that the VCC pin of this IC, LD5760, was showing reverse leakage. I will also show you the picture below. Well, my diagnosis was that this IC is faulty and will have to be replaced. I couldn’t find a new IC, so I found this IC from an old motherboard and replaced it. I also tested the related resistances very carefully, especially the current sense resistor pin number 3 of the IC, which is the current sense pin. A 680-ohm resistor is placed here. See the pictures. 

Dead Fault Successfully Fixed

In such a fault, it is a normal condition for the IC LD5760 to fail because, after all, the IC has its own life. Here you have seen how we diagnosed and solved this. The whole thing is still pending. I first cleaned the entire circuit and then replaced the IC and fitted the MOSFET circuit board. Now the next step was to switch on the power supply. I turned on the set and checked 12 volts with a multimeter, and it was present. I checked the 12-volt reading very carefully to see if it was too low or too high. It was exactly the right value, which meant that the circuit was in perfect working order. Now I released the set from standby, and it has great picture and sound performance. My dead fault has been fixed. 

• Power supply dead fault.
• IC LD5760 With VCC pin leakage With ground. 
• It was an internal fault of the IC. 
• We replaced this IC and our power supply fault was fixed.

Essential resistors marking

The images below have marked the necessary test points and resistances, and the current sense resistor is also shown, along with its value. 

Final Testing & Results

Since this fault was such that its final testing was extremely necessary, I ran this set for 6 to 7 hours, turning it on and off repeatedly. This was also necessary because this set would turn on occasionally before, so I did a very hard test of it. I tested it on a cable channel and tested it thoroughly by giving a signal to its HDMI port. As soon as I had my own satisfactory testing done, I then informed the customer that his TV had been repaired. Sony LED TV Repair Center Lahore never compromises in its work, and we then publish these case studies on our website so that technicians around the world can benefit from them.

My experience with such cases

In cases of power supply faults, I would say that first you should have a complete understanding of the theory of the circuit, what topology is used in it, and which IC it is, and get information about that IC. Then there can be no difficulty for you. Today, the resistance value in the circuit board is not fixed. The need for experience and fresh knowledge has increased a lot to work at the chip level. Only if you keep yourself updated can you get a quality level of work done; otherwise, it is easy to replace the entire main board, but I don’t call them technicians; these daily wage earners are, in my opinion, just day laborers. They should be avoided. 

Conclusion 

TCL L32S65 Power Supply Repair Guide This LED TV annoyed me a lot because its fault was something like this: an intermediate type, sometimes on and sometimes off, meaning it would generate 12 volts of power supply as per its own wishes. Above, you saw how we did it. Diagnosed this fault and resolved it. Actually, its main power supply was intermediate, and its VCC pin was showing leakage with ground. This may have happened due to excessive use of the set. It is often seen that people keep their led tv plugged in all the time and turn it on and off using the remote. This behavior is wrong and needs a change.

FAQ

Q: 1 My TCL L32S65 TV won’t turn on at all, no light, what is the problem.

A: 1 This could be a fault in the main power supply. You should check the 12 volts. 

Q: 2  Where can I find a TCL L32S65 power board (TPD.NT72563.PB771) or how much does it cost.

A: 2 I don’t know about its cost, you can search this board on Google and you will get an idea. 

Q: 3  My TCL 32-inch TV powers on but the screen stays black, what should I do.

A: 3 A black screen usually indicates a backlight failure, and in this model the backlight circuit may also be faulty. 

Q: 4  Can the TCL L32S65 power board be fixed at home by myself.

A: 4 If you are not a technician, you should not try to fix it yourself. Contact a qualified person. 

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