Sony TV standby LED blinking 6 times solved
A customer requested me to repair his Sony TV model: 46BX450 with panel defects. He commented that somebody had quoted him the price of a new panel is so expensive that it is not worthwhile to change it.
When I turned on the set I observed that the standby LED blink six times with the Sony Logo appeared briefly on the screen before it shut down indicating that the backlight was working. According to the Sony service manual the fault lies with the panel assembly and recommended to change it.. The term “panel assembly” on the service manual include the backlight inverter board, CCFL lamps and the LCD screen.
Since the inverter backlight board is easily accessible , so I proceed to check it first. On analyzing the inverter board I notice the connector pin 11 (ERR_OUT) of CN101 has an error feedback voltage to the main board (photo 1). Photo 2 showed the measured error voltage of 3.6v which is high and it is supposed to be near zero volt
The 3.6V feedback error voltage confirmed that either or both the inverter board and front LCD panel were faulty. The main board protection mode will be activated and will shut down the TV upon receiving this error voltage ERR_OUT. On the inverter backlight board there are 3 high voltage transformers (part no:34018AD) which are prone to failure i.e T100,T200 and T300 (Photo 3). Testing these high voltage transformers are complicated but the inductance measurement will be able to tell whether it is faulty. Since the 3 transformers are identical with the same part no. , we can compare the differences in the inductance measurement.
Part no: SSI460_12F01
T100 has very low inductance probably with shorted turns as compare with T200 and T300. The protection circuit of the inverter must have sense the abnormal drives to the defective transformer or unbalance load on the CCFL lamps and caused it to generate an error voltage to trigger the main board to shutdown. I wanted to change the inverter backlight board or transformer but unfortunately either part is out of stock in the market.
Finally, I found a supplier in China who can offer me an alternative board which can work with this model. Physically it does not looks compatible with the original Sony but the supplier insist that it can work. The price is attractively low so I give it a try. Photo 4 show the replacement board from China with magnetic feet for the screw holes since it dimensionally different and with plug-in pcbs & wires to the appropriate high voltage brackets of the CCFL lamps.
I would expect the TV to work after replacing the backlight inverter board but disappointed that the fault remain as before. I suspect there are more than one faults responsible for the shutdown.
Next, I removed the front LCD panel screen to check on the CCFL lamps. Since I do not have CCFL tester to verify each individual lamp working characteristic, I have to rely on common sense and visual judgement. Some of the lamps have excessively large area of black ring on one end, I guessed these were faulty or leakage lamps (Photo 5).
I changed a few of the CCFL lamps which are with excessive dark ring. The panel were re-assembled back and power on with China backlight inverter board. I make the correct judgment, the video was able to turn on now and the shutdown does not reoccurred. The error voltage ERR_OUT measured is 0.036V with the China backlight inverter board as shown in Photo 6
I want to re-confirm the original backlight inverter board which I suspect was faulty, so I replaced the China board with the original Sony backlight inverter board. When power was turned on, the shutdown fault re-occurred. Now I can confidently conclude that the original sony inverter backlight board and those CCFL lamps with excessive large black rings were defective.
In my personal opinion, a better solution will be to change the high voltage transformer rather than changing to another version of the backlight inverter board. In this case I have no other option unless I am able to salvage the require part from another defective TV. I have also tried interchanging T100 and T300, by chance I was able to switch on the TV without shutdown fault. The error voltage measured on the Sony backlight inverter board is 0.04V only (Photo 7). The only problem was the backlight was not evenly lighted up and a faint dark horizontal band can be seen on the screen with high contrast video.
The customer was very happy to see the TV working again and the repair cost is very much cheaper than the price of a new panel.
I hope this article will be useful for those who encounter similar problems with Sony LCD TV. It may not be the best solution but it provide an alternative solution rather than throwing it into the waste dump .
This article was prepared for you by SK Wong from Malaysia and he graduated from London with a degree in Electronics and Electrical Engineering. He has more than 40 years of experience in the consumer product manufacturing. With the passion to repair electronic products from young , he has been doing it part time until now.
Currently, he can provide turnkey solutions for consumer products including services from idea or concept to design , prototyping , finished products (including electronic,mechanical and plastic parts) and manufacturing.
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