KLV-46BX450 startup logo then blank screen

KLV-46BX450 startup logo then blank screen – CCFL Tube Holder fix

Introducing

The KLV-46BX450 startup logo and then a blank screen were brought to my workshop for repair. The customer said that we were watching a program and suddenly this happened. I turned it on and saw that it showed the set logo, and then the screen went completely blank. Surprisingly, it was not showing the protection show, although usually a six-blink fault show occurs in such a fault, but this was a unique case in that it showed the logo and the screen went blank, and after that its green LED remained on and sound was also heard. I took time from the customer and told him that it was okay; you leave it alone. I will diagnose the fault and then tell you what the cost will be, and after asking you, I will fix it.

KLV-46BX450 inverter board test

I opened this set in my workshop lab and first cleaned it because there was a lot of dust inside it. Now I connected it to AC power and examined it. Its backlight would light up for a while and then turn off. Since this model is quite old, CCFL tubes are used in it. I checked the voltage of its CCFL inverter. It was 24 volts. Three points, three volts, were coming on its enable pin. There is a cover on it. I took it apart and saw that the PCB was fine. To check this inverter, I put a neon lamp on its high-voltage coils and saw that the coil was producing high voltage. This meant that the inverter was working. At the same time, I felt some strange smell, like something was burning. I immediately decided to open its screen.

Sony KLV-46BX450 CCFL Tube Holder Fault – How to Identify & Fix

To open the screen, first I opened its plastic front cover, then after opening it, I separated the screen and also separated the diffuser sheet, and then I saw the fault. This model had twelve CCFL tubes installed; both sides of them were covered with plastic. I separated the master side cover, and then I saw the holders of its CCFL tubes were faulty. These holders were affected by electrochemical corrosion. Each holder was creating chemical corrosion with the body. I took out these holders with great care. After taking them out, I cleaned their chemical corrosion, and after that I sprayed on them so that they would not be affected again. After that, I fitted these holders in the body with great care, and then I fitted the screen.

• Opened the plastic front cover to access the screen.
• Carefully separated the screen and diffuser sheets.
• Found the fault after full disassembly.
• Removed the master side plastic cover to inspect tube holders.
• Found CCFL tube holders damaged due to electrochemical corrosion.
• Each holder was chemically reacting with the metallic frame.
• Carefully removed the corroded holders.
• After cleaning all the CCFL holders, the fault was completely resolved.

CCFL Inverter Board Replacement in Sony KLV-46BX450 – Quick Fix Guide

After that, I installed its inverter board. My set was properly turned on, but I felt that its light was low. So I started looking for the reason. I inspected the inverter board very carefully. I found that one of the coils was different. It has three large coils and one small coil. There was a difference in one of the three large coils. I checked its continuity with a meter. There was a clear difference. I thought that maybe a technician had changed this coil. This coil was actually a 40-inch set, which is different from the 46-inch set coil. That’s why the light was low. So I had to change the entire inverter board. When I changed it, its brightness became perfect, and my fault was fixed.

Conclusion

So you saw how we repaired an old model Sony. It had a backlight fault. But this fault was in two places. First, its holders were damaged. We repaired them. Second, its inverter was damaged. We replaced the inverter. The reason for this was that someone had installed a 40-inch coil in it, due to which the high voltage was getting low and the light was low. And when we installed the second inverter board, the brightness was complete. And thus we had a very long job. This and the sensor were also there. The sensor is because it has CCFL rods installed in it. Or you can call them rods or tubes. They are very delicate. You have to handle them with great care.

Q1: Arcing Corrosion What happens and how is it created?

A: When high voltage creates an electrical arc (spark), it produces heat and gases that oxidize (rust) the surface of the metal. This rust is usually a black or blue smoky substance.

A2: When electric current interacts with moisture and metal, a chemical reaction occurs that takes the form of rust or corrosion. This is often seen at connectors, pins, or soldering points.

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