Samsung BN44-00175A SMPS clicking (No 5.3V)

[Hawk2112]

Have a 50inch plasma with a faulty power board. I replaced the standard faulted caps and it worked again for 3 more weeks but has failed again.

I have replaced the caps again to be safe (CB814/14 and CX834/35) with Panasonic FM's but still not joy. LED fault code is for the 5.3V

(While Clicking)
STBY =5.195V
Vs =0.2V <-- I understand this one won't come up until this Vs_On is +5.3V
Va =65.1V
Vg =15.07V
12 =12.0V
Vamp= 18.2V
5.3V = 0.72V <-- only one out of range
Fan = 7.92V

I have continuity on the +&- side of all the caps (a suggested issue) but all test good.

Any suggestions on what to test next?

Anyone have a schematic for this beasty?

Thanks in advance..

[flocko]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

Hi there are no schematic for this board, but I can tell you that if you have all the other small voltages the main transformer is working, and I that the 5.3v rail is a stand alone tapping off that transformer, check components on the last heat sink (diodes and fets ) as this rail has to rectified and regulated from the transformer ? best to look on the back of the board and trace the 5.3v output back towards the heat sink, you say you have changed caps and given the numbers but this means nothing to us as we don't no what ones these are and the rails they are on , sorry I cannot give you more info but I hope this is of help Flocko

[Hawk2112]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

Attached some new pics. I have a small IC that is causing the issue but it appears to have the ID removed.

If I apply my soldering iron tip to the top of the IC for 5 sec, the 5.3V rail starts normally and the SMPS runs fine (for a while).

PIC#1 idents the 5.3V rail and the IC in question.
PIC#2 is a closer shot of the IC.

Any suggestions on how to proceed or is this a lost cause?

[flocko]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

not 100% but by the way pins 6/7/8 are linked and tied to the - side I would say it would be a KIA393F voltage comparator , try cleaning it up a bit and see if it has A393 on it, these are used a lot on Samsung P/Bs in the detect circuits

[Hawk2112]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

Tried everything but the surface is rubbed away for some reason.

[lookimback]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

It looks more like dried up flux on that IC. I would try a bit of acetone on a Qtip.

[Hawk2112]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

Lookimback was right and upon better cleaning 25H3LL can been seen so they are Power MOSFET for DC/DC conversion.

I reflowed the ICs and its working again. I am going to order the chips and have them on hand if/when it acts up again.

[micasF]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

Hi, have a issue on this board.
Have a stb: 3.09V and the rest is all 0,xxV
Can anyone help me?
The normal capacitors are in god conditions and measurements...
thank you,

[micasF]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

Hi, have a issue on this board.
Have a stb: 3.09V and the rest is all 0,xxV
Can anyone help me?
The normal capacitors are in god conditions and measurements...
thank you,

And PS ON is on 2,7V... when i ground it it does nothing......

[EETVS]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

I have the same problem, I have replaced the 25H3LL with a IRF7862 from RS components part number 495-887 , and so far so good

So a big THANK YOU ,

To all of you for the posting , saved me a lot of hair pulling

Kind Regards
Ken

[Newbie62]

Re: Samsung BN44-00175A SMPS clicking (No 5.3V)

i have the same problem, i have replaced the 25h3ll with a irf7862 from rs components part number 495-887 , and so far so good

so a big thank you ,

to all of you for the posting , saved me a lot of hair pulling

kind regards
ken

495-887 is heat shrink tubing !