Samsung powersupplyboard PD46B2-BDY clicking

[Tony.T]

UE40N7005 TV.

When powering it on. The relay starts clicking after 10 seconds.  Disconnecting the PS:on from motherboard makes it stop and i see that my testlamp is glowing 20%. The mainboard is running and consumes some current.

But as soon PS:on is connected the mainboard shuts down the powersupply.   if i connect 5V....12V and 63V to the diodes after the transformers from external powersupplies.  And of course disconnect the board from mains...everything works.  The TV turns on. picture present.    So something is not working correcty when it produces its own power.

But the confusion that i have now.  Is that when connected to mains.  Everything is silent...no clicking at all.  BUT...  The 12V is present....the 85V is present even if the boosting to 135 is not activated for the leds.

That DISPITE me doing nothing with PS_ON.  When i measure PS_ON it is 3,5V.       As soon i ground PS_on....the relay clicks and turns off the mains.  in my world..this board should only produce 5V via a smaller transformer...with it does.  But no 12V and no 85V swithing.   As soon as ps_on is grounded...the switching should start.  That would be the normal...RIGHT???  OR???

If only 5V was present...and no 12V and no 85V....and if i ground the PS_on and THEN the relay was clicking to turn everything off...then of course it would be exlplainable that something is shorted etc.  But now almost all voltages are present...except for the boost part for the leds...from 85V to 135..when doing nothing to ps_on.

Can someone explain anything around this? Am i thinking wrong?  Any ideas what it could be?

Thanks in advance.


ohh---in the attached picture.  I have marked with red where the tracks go from PS_on.  One part goes to a transistor that runs the relay...and also to other part of the card where the optocoupler for 12V is.

When external powersupply is used ...i got 1.1V over the optocpupler on the led side..... on all three places....

[Tony.T]

Well...wrong by me.

PS_ON is set to high automatically.  To turn tv on.  if i pit ps_on = low ...then the board is silent and only 5V present. As soon  iturn on tv with remote ...ps_on is set HIGH and board starts SWITCHING.

That if i run on external supplies.    But as soon i try powerboard against mains then it start clicking.   The conclusion is that something is drawing to much current probably and turns off.  Must be leds ??!!

I opened the screen and removed led. All of them seemed to be ok.  Measured sequence by sequence and added all the voltages.  Ca
me to 130V which is the same as the board is outputting.  So maybe currentdraw to high.   

if you look at the pinout of leds...there are a lot of lines....the two cables are full of wires.    i would be able to turn all the leds on with my ledtester.. to see the current consumption.... any ideas how? 

Or how to dim the leds and don´t let them draw that much current.....