Samsung UE32C4000 PSU pulsing

[gazzagadget]

Hi all, newbie  on here but ex old school TV & video engineer, now in IT support for TV production industry.
 
Been asked by a friend to take a look at this Samsung UE32C4000 set.
Standby LED comes on, switching on with remote the PSU starts up then after a second or so protection shuts it down, then repeats cycle on for 1 second, off 5 seconds, forever until power removed. No visual signs of usual PSU suspects, stressed caps etc.
12V OP rail pulses up to 12V.

Power supply board is PD32AF0E-ZDY.

Has anyone a schematic of this PSU please, or any known faults like this on this set?

Many thanks in advance.

-Gary

[jordan]

http://elektrotanya.com/samsung_ue32-37-40-46c5xxx_ue32c4000px_chassis_n92a_sm.pdf/download.html

[michael first]

Hi,GG

power on, with cable from PSU to main disconnected;if the backlights remain on,main defective if 

not, PSU is the culprit (bn44-00351b).

[jordan]

bn44-00351b

[gazzagadget]

Many thanks for the replies and info, I'll let you know what I find.

-Gary

[gazzagadget]

Thanks again for the PSU schematics.

I spent some time investigating and testing for the problem and could find nothing wrong on the PSU. I admitted defeat got a replacement PSU board and the problem persists.
The D12v & Vamp supply rises to ~12.5v for about a second then drops back to 0v for about 5 seconds and the cycle repeats. The 5.2v standby supply is OK and constant.
So attention to the main board, has anybody any experience of fault finding this board and/or any information, circuit diagram etc please?

The board code number is BN41-01549A - X4_LED_LARGE.

Thanks in advance.

Gary

[michael first]

Hi,check IC203(I/P pin#2,O/P pin#7,8) IC204(I/P pin#2,O/P pin#7,8) IC202(I/P pin#1,O/P pin#3) and

Q202(I/P pin#1,2,3 O/P pin#5,6,7,8);all these IC's are fed with B13_PW.

you should check BD222,BD220_D,BD219,BD210_13,BD240_5 too;they're mounted next to

CN210;also check for short circuits all the smd capacitors mounted at the inputs of the fore mentioned

IC's to GND.

[gazzagadget]

Thanks for the advice, I'll check those out as soon as I get some time.

Gary

[gazzagadget]

Thanks for the advice but on this one I conceded defeat, boxed it up and will give it back to its owner.

I had a good poke around on the main board and couldn't find anything unexpected. But I did find slight traces of something sticky on the back of the main board, I can't be sure but it seemed suspect and that it shouldn't be there. That said I could see no way anything could be spilled here, no vents above the board in the rear cover, no trace of the suspect substance anywhere else except on the VGA connector.

I can only spend so much time on a freebie job and this was turning into a PITA.

If anyone is interested in the BN44-00349B power board I bought, it's on fleabay.

Cheers for your advice