Samsung led tv #UA32C4000PA with no backlight

[playstation1200]

hello badcapians!
I have a samsung led tv model#UA32C4000PA with a power board model#BN44-00349A which I'm trying to repair.
the tv starts normally. passed flashlite test for picture. sound ok. only issue is theres no backlight from the tv. overall visual inspection found nothing fried or burnt. all capacitors and other components look good.
I tried to first check the power output from LED driver pins thats marked +led1. it shows a measurement of +85-89v while the -led pins shows 0. I tried to open the entire panel for checking the led's on the strip. all LED's seem to be fine. checked all the led's individually. the led strip is divided into 2 halves each containing 50leds,total 100.althought almost few led's towards the end of the strips look a bit darker than others but they do glow individually when 3v power is supplied to them through a battery. while diagnosting I found a small chip(possibly caled the pwm IC)with thermal protection over it was making a very suble noise like those which u hear from a laptop harddisk which is tring to access data(kirkirkirkirkirirkri!!!). i pressed the heatsink 3-4 times and suddenly the power on the +led pin bumped to 321v...after i connected the led's it immediately started the backlight and I got my backlight on again. but once i switched off the tv and tried to restart the same problem started again. now even after pressing that IC nothing is happening...the voltage is same 85-87v(both when led's r connected as well as when the led strips r disconnected). can someone throw some light on which part of the board could have gone defective. how to identify and troubleshoot the root cause.
I've Attached an original reference pic of my powerboard. I'll try to upload the entire original pic of the powerboard and main board too.

[Andrew F. Ali]

Re: Samsung led tv #UA32C4000PA with no backlight

Try soldering the pins on the IC. If that doesn't work look for cracks/break on the circuit board near the IC, and if that doesn't work direct replace the IC.

[budm]

Re: Samsung led tv #UA32C4000PA with no backlight

This board is also known for bad solder joints, especially the legs of the transformers and power devices that have through hole rivets.
The 85~87 V is the feeding Voltage to the Voltage boost converter circuits for driving the LED strings, it comes on when BL-ON is present, if it detect open circuit in the LED output or over current condition then the Boost converter will go into shutdown so the output at the LED+ will drop back down to 85V.

[playstation1200]

Re: Samsung led tv #UA32C4000PA with no backlight

Try soldering the pins on the IC. If that doesn't work look for cracks/break on the circuit board near the IC, and if that doesn't work direct replace the IC.

i tried to check the voltage on that ic. the voltage on pin 1 starts at (+-)190-200v and drops down to 0...the rest of the pins stays at 0.9v. I've attached an image of the actual board with real voltage output mentioned on some of the pins. plz have a look.

[playstation1200]

Re: Samsung led tv #UA32C4000PA with no backlight

This board is also known for bad solder joints, especially the legs of the transformers and power devices that have through hole rivets.
The 85~87 V is the feeding Voltage to the Voltage boost converter circuits for driving the LED strings, it comes on when BL-ON is present, if it detect open circuit in the LED output or over current condition then the Boost converter will go into shutdown so the output at the LED+ will drop back down to 85V.

so exactly which part should i start checking from voltages or the circuit. coz i've checked all the leds in the string and all are ok.check the above post.i've attached a pic of the powerboard mentioning all the voltages im getting from the circuit.see if u can find anything. and why theres no voltage power from 2 of the resistors(i've marked them with thr zero voltages.checked the resistance of the pins,seems to be ok with 0.6ohm resitance)