Sony KDL-60NX720 Failed after 1 1/2 years! 4 LED Blinks

Hi,
I've got the KDL-60NX720 that has now failed. When I power up, the screen comes on, led goes green, then after about 3-4 seconds the screen shuts down and I get 4 red led blinks. The "helpful" tech at Sony support says I need to bring it to a repair facility because the code is a failed board or screen problem. (Wow, that was helpful). Searching around I've found some sites say the 4 blinks is related to the backlight.

I am fully capable of fixing this myself once I find the problem (even to the extent of replacing hi-density SMD's). If anyone can provide any information as to the real failure and the fix, that would be appreciated. I'm sure I'm not the only one with this issue.

I've searched the net for a service manual but cannot find one for this set. If anyone knows of a source for the service manual, please post.

Thank you!!
Bob

Hi, thank you for your reply. I've see a number of different code tables for Sony's. Do you know if that one is specifically for my Bravia set? Also, is the "balancer" the name for the inverter board for the LED's?
Edited by firemanbob - 1/12/13 at 10:33am

Hi,
I a little confused by the terminology regarding the boards. So far we've got the balancer, main board and power supply.
When I open the set back, I see a main power supply on the left. I checked the marked voltages coming from this board and they all appear to be correct (standby 3.3, 12 and operational 12).
This board feeds another power supply board (what I'll call the LED power supply) in the upper center of the back that appears to be the LED power supply judging by the silkscreen for the connector pins (LED Vcc, LED Gnd on multiple connector pins). Looks like this board takes AC from the main power supply, has an on-board switcher with dual planar transformers that feed an output section that has a good number of power resistors and electrolytic caps in parallel. The output from what appears to be the + and - rails on this board go to a connector with multiple shared pins labelled LED Vcc and LED Gnd, along with LED Err. That connector feeds another board (which I'll call the LED driver) in the center of the back that has 5 small ribbon cables going into the LED array. There's another ribbon cable going to another board just below it..
What I've done so far, in addition to checking the voltages coming out of the main board is:
1) Monitored the LED Vcc and LED Gnd while powering up on the LED power supply board. This voltage goes up to about 35vdc then drops when the screen shuts down.(Chicken or the egg?)
2) Disconnected the LED array from the LED Driver board and monitored the LED Vcc and LED Gnd on the LED power supply. With the panel disconnected, I get about 55vdc before it shuts down.
3) Disconnected the LED Driver board completely. Get the same result on LED Vcc as above in 2 on the LED power supply.
4) Connect each LED ribbon cable on the LED Driver board one by one and monitor the LED Vcc. In each case the voltage comes up to about 35vdc before the set shuts down.
5) I've taken the LED power supply and LED driver out and inspected for burnt/open/shorts/damage. They both look fine. The fuses on both boards are ok.
There's no marking on the LED driver board or 2nd power supply as to what the voltage should be. I can't isolate to either the power supply or the driver board since without the driver the supply gets to 55vdc. With the driver board connected, all the LED's come on for a few seconds.
I guess I would have expected the set to stay on if I removed the board that was causing the problem.
So what exactly is the "balancer" board?
Any ideas would be helpful. Thank you.
Edited by firemanbob - 1/12/13 at 6:24pm

Ok, so moving right along here, I've been able to get the set up and running by disabling the BL_ERROR signal from the main ps to the controller. I now get a picture but what I see is a dark area in the lower right of the screen. I guess the LED edge/backlight is indeed bad and not the electronics.

HOW THE HELL CAN SONY SELL THIS CRAP! 1 1/2 year old set and the LED backlight is bad and warranty is expired! WTF!

The general belief in the industry is newer is better so since LED's are new, they must be better. What a bunch of crap! I have an LG LCD with ccfl that's 5-7 years old and running strong. Since this set is no longer under warranty, Sony can go to hell. But here in the USA, if they were to even mention that they were going anywhere, I'm sure the hand-out administration would fork over a few hundred million to "bail" them out. Guess this is their way of getting us back for the bombs.

I tried swapping the ribbon cables from the LED driver (G7) (there's 5 identical cables that go to the screen) to see if the dark area followed the board or stayed in the same place. When I moved the cables, I was not able to get the backlight to come on at all. Without the schematic for this board, I'm shooting in the dark. I would like to try and isolate the problem to find out if it is indeed the G7 board. That would be an easy fix. Not sure if it's possible to fix it if it's the LED array in the screen. I took a look last night at removing the trim around the screen and the screen assembly appears to be one unit encased in a metal frame. I was hoping I could get to the offending LED section and do something to test it.
Do you know how this edge LED array is assembled in the screen and if it's possible to just remove that part of it? Also, any ideas on trying to isolate between the G7 and the LED array?
Thank you.

Ok, thanks. I'll have a look. Hopefully I can find another set that uses the G6 and G7 boards for LED drivers.

I got my registration from the test for that site. Correction on the boards, it's the YL board that I think is bad (ST4055YL-S01).
I could not find the schematic with the chassis for this set.