Root Cause: 1.2V Core Voltage Drop

klv-40W652D dead fault let’s learn how to solve this fault. The symptom was that the TV was not turning on, and the red standby light was not showing either. The core voltage of its MediaTek system IC was generating a very low value—0.987 volts—whereas the correct value here should be 1.2 volts. According to my experience, this can be the reason why this set is not turning on. In this model, a 6-pin SMD IC in the core-voltage regulator section, along with an inductor coil, performs this function. There are many other reasons why this specific Sony series may not turn on, but in this article we will focus on the 1.2 V voltage drop. This issue will be explained step by step.

Finding the Fault: Voltage Tests

I opened the back cover of this set and examined the main board, then cleaned it. After that, I tested its main 19-volt power supply, which was present. According to the sequence, the next step was to test the 5-volt line, and it was also present. Then I tested the 3.3-volt regulators. These are two small SMD ICs whose input comes from 5 volts and whose output is 3.3 volts, and here too the voltage value was correct. The next test was for the core voltages of 1.5 and 1.2 volts. Out of these, the 1.5-volt line was providing an accurate value, but the 1.2-volt line was very low. My multimeter was reading 0.987 volts at this point, which was the reason why this set was not turning on. Now I had to find the cause of this voltage drop.

1.2V Regulator: Feedback Network Analysis

Here we will analyze this 1.2-volt regulator circuit. This supply is rated at about one to one and a half amps, and its input is 3.3 V. It is designed as a buck converter and provides a constant 1.2 V supply to the system IC. It does not allow even the slightest increase or decrease in voltage; otherwise, the system will not function properly. This circuit consists of a 6-pin SMD IC, an inductor coil, and a few resistors. The most sensitive part of this circuit is its feedback section. A voltage-divider resistor network is used on the feedback pin of the IC. It consists of three resistors: one resistor is connected to ground, while the other two are connected to the output of this circuit. Even a slight change in the value of any of these three resistors directly affects the output voltage.

Repair Steps: Testing & IC Replacement

Above, I explained the structure of this circuit. Now I had to find the cause of this voltage drop and resolve it. First, I tested the feedback section of this circuit. I carefully removed its three resistors from the PCB and checked their values, and all of them were perfect. I have written these values down, so I am speaking with confidence. After that, I checked for any short circuit at the output of this circuit, and that also appeared normal. At this point, only the IC remained as a possible fault. I decided to replace it and observe the result. The original IC was not available, so I removed a similar IC from a Chinese board. The IC was the same, only its power rating was different. I installed this IC on my board and, after cleaning the area thoroughly, it was time to test whether the 1.2 volts were correct or not.

Success! TV Fully Repaired & Working

I cleaned the main board thoroughly and fitted it to the TV in the area where I had worked. After making all the connections, I provided the main board with a 19 volt supply from the adapter. First, I turned on my multimeter.I tested it by applying it to the output of 1.2 voltage, so the circuit started producing its full and accurate 1.2 volts here. I saw the red standby light turn on, confirming the first sign of life. Now the next step is to put the set in standby Mood I turned on the set with the remote and looked at the screen with the backlight on. The display was also on there. I gave it a signal on the HDMI port so that its screen could be tested. This klv-40W652D dead fault fixed. 

Final Verification & Stability Test

The nature of this fault was such that it required thorough testing. My first test was to monitor the 1.2-volt output with my multimeter for an extended period to confirm whether the voltage remained stable or fluctuated. Since the IC used in this circuit was not original, I decided that it would be better to replace it with a genuine one. The next day, I completed the job by installing the original IC and placed the set on a rest run. For two days, the TV continued to perform perfectly with absolutely accurate operation. After being fully satisfied with the results, I informed the customer that his Sony TV had been repaired. You can find more troubleshooting articles from this series on the Sony LED TV Repair Center Lahore website.

Fault Summary & Repair Steps

• klv-40W652D dead fault
• Symptom: TV completely dead, no standby red light.
• Diagnosis: All mainboard voltages normal except the 1.2V core rail, which measured only 0.987V.
• Testing Performed.
•   All components in the 1.2V circuit tested.
•   Feedback resistors measured correct values.
•   No short circuit found on the 1.2V output.
• Root Cause: Faulty 6-pin SMD buck converter IC in the 1.2V regulator circuit.
• Solution: Replaced the faulty 6-pin SMD IC with a genuine part.
• Result: 1.2V restored perfectly, standby light ON, TV fully functional.

Expert Advice for Sony TV Repairs

The specific thing about Sony LED TVs is that they have many common faults, and for this, you should always take the help of a senior and experienced technician. I say this because when certain faults repeatedly occur in a particular model, they are classified as common faults. Trainee mechanics often make these faults even more complicated, and as a result, the TV can become unfixable. In such cases, the only option left is to replace the entire motherboard, which is far more expensive than chip-level repair. My advice is to insist that your TV be repaired at the original board level by an experienced technician. If someone suggests installing another board instead, then either he lacks proper expertise or he is not a professional.

Conclusion 

KLV-40W652D Dead Fault you saw how we diagnosed the dead fault of this Sony LED TV. The standby red light of the set was off, indicating that it was completely dead. The main board of this TV had a 1.2-volt drop, and we solved this problem by tracing it step by step. This is a chip-level repair guide. Its 1.2-volt regulator circuit was faulty, and the 6-pin SMD regulator IC was not working properly. Initially, the fault was fixed by replacing it with a Chinese IC, and later, it was replaced with the original and genuine IC because I was concerned that the Chinese IC might cause problems again. Sony LED TV Repair Center Lahore always provides quality work.

If you want to read about the fault “How to fix Sony KLV-40W652D not turning on”, click here.

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