Sony KDL-55BX520 powers on to green light but no boot

[keysal]

I have not been able to find a service manual for this TV anywhere on the internet, neither free sites or for pay. It just doesnt seem to exist.

I came across this video from Coppell TV that shows how to diagnose and repair the power supply APS-311 1-885-143-11.

https://www.youtube.com/watch?v=1ziLm_yPUQI&t=5s

I checked the pin voltages and they seem fine. STDBY was 3.5 and the 13V pins were 12.8. I didnt read the 400V capacitor yet because I wasnt sure the proper procedure. Whether between the capacitor legs or from the positive of capacitor to some hot side ground?? avoiding sparks is ideal.

The main board uses a MediaTek MT5388 SOC in a BGA package that gets hot as a pistol when plugged in and on. It seems to turn on automatically If I disconnect the keypad and I have been able to get the back light to come on and once it even showed a "no signal on HDMI 2" on the screen but without the keypad attached and no remote control I wasnt able to test other connectors like the tuner etc.

I wanted to see if I could get a video signal to the screen I turned off the tv and hooked up a video camera to that hdmi port but I couldnt get the TV to turn on again with the cable hooked up.

I noticed Shop jimmy is out of stock of the main board but does have a repair kit for the power supply that involves a fair number of components to replace.

I'm wondering if there is a way to stress test the power supply to make sure if I need that kit or not.

I have found other main boards and I figure I should probably go ahead and get one but would like to make sure the power supply won't kill it.

When I pushed down on the mediatek chip with pliers and added power it turned on back light and it seemed like the chip took longer to get hot which so far has gotten to 80 Celsius range. After power is off it seems to cool off quickly enough. Im tempted to flood BGA with liquid flux and try to reflow to see if maybe some whiskers had formed between solder balls causing a short. I noticed a lot of reballing kits and stencils for this chip type.

Awesome Girl Friend got me a hot air solder station for birthday and I sure would like to get this TV working to give her in Time for Game of Thrones.

Any ideas?

[attainteddragon]

Re: Sony KDL-55BX520 powers on to green light but no boot

The main board uses a MediaTek MT5388 SOC in a BGA package that gets hot as a pistol when plugged in and on. It seems to turn on automatically If I disconnect the keypad and I have been able to get the back light to come on and once it even showed a "no signal on HDMI 2" on the screen but without the keypad attached and no remote control I wasnt able to test other connectors like the tuner etc.




When I pushed down on the mediatek chip with pliers and added power it turned on back light and it seemed like the chip took longer to get hot which so far has gotten to 80 Celsius range. After power is off it seems to cool off quickly enough. Im tempted to flood BGA with liquid flux and try to reflow to see if maybe some whiskers had formed between solder balls causing a short. I noticed a lot of reballing kits and stencils for this chip type.



Any ideas?

i think that you have answered your own question.

either reflow or reball the bga, or replace the main board and you should be all good.