A Quick Tips on How to Bypass 4X LED Blinking Error for Sony KDL-55W900A Smart LED TV

Today my friend brings in a Sony KDL-55W900A Smart LED TV with complaint TV not working with front red LED light blinking 4 times then stop about 3 seconds, and then continue to blinking 4 times again and non-stop. Since this TV is urgent need to use now, so my friend asked me is it possible to solve this TV problem within 30 minutes?!

Refer to the Sony KDL-55W900A service manual “Standby LED Error Display” and found this 4x LED light blinking/flashing error is a LED Driver error (LD_ERR) or Panel Module/LED Screen error.

For us, as a TV repairer, know that it could be the LED driver circuit/section (power supply board) especially their feedback circuit abnormal, connection (or cable/s) in between the PSU board to Panel LED strips abnormal or the LED strip/s itself abnormal. This Sony KDL-55W900A Smart LED TV is using the APS344 (CH) or 1-888-119-11 or 1-474-484-11 power supply board with built-in LED driver circuit.

Unfortunately, this part number of PSU board the stock is temporary not available now. So just told to the friend and ask him to give me 30 minutes try to troubleshooting & repair it. 

First, use the LED TV Backlight Tester to test this TV backlight unit, and it is looking good and the backlight is lit normally. Second, check the PSU board and find all the output voltages looks good. Also check the LED driver circuit and no any shorted components there. I suspect their LED driver feedback circuit component/s or etc abnormal. I think to use the Bypass method to check or confirm it is their LED driver circuit feedback abnormal. Third step is to connect a wire from CN6401 connector pin-3 (BL-ERR) to Ground (GND) is to bypass their error protection. 

After connected the wire to bypass their backlight error protection, power on the TV, the TV can display a perfect display and problem solved now. So, this is to be confirmed that the PSU board LED Driver feedback circuit was abnormal and cause this problem to occur. Since it is an urgent case, my friend is very happy to bring the Sony KDL-55W900A Smart LED TV back with this temporary solution. I highly recommend him when he is free to bring back the TV to solve their feedback circuit or replace a new/working PSU board for safety purpose. 

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