Samsung LNS4051DX wont turn on

[SHADOW3277]

Picked up a Samsung LNS4051DX off of CL. When plugged up the tv, the standby light would flash rapidly. Took the back off and found no bulging caps. I took a hairdryer to the caps in the top right hand corner and the power supply start clicking slowly then fast and then the tv came on.

I replaced all the caps in the top right corner (12 of them) with Rubycon ZLH caps. Plugged the tv in and the standby light still flashed. If I take a hairdryer to those same caps the PS starts clicking and then the tv will turn on. So I replaced those caps a second time and the same thing still occurs. I had a spare mainboard laying around so I tossed that in the tv just for the heck of it and the same issue occurs.

Anyone have any ideas? Thanks

[Moreno83]

Re: Samsung LNS4051DX wont turn on

Heat is moving pretty fast over the whole board so try to isolate the area with a little heat.
It can be that a part on the bottom of the board is warming up when you are applying heat on top of the board....

[budm]

Re: Samsung LNS4051DX wont turn on

Check and see the standby Voltage is going up and down in sync with the clsiking of the power relay do the same checking on the PS-ON pin.

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

Heat is moving pretty fast over the whole board so try to isolate the area with a little heat.
It can be that a part on the bottom of the board is warming up when you are applying heat on top of the board....

Thanks for the reply. I tried placing a shield around the area, low heat on the hair dryer, same symptoms.

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

Check and see the standby Voltage is going up and down in sync with the clsiking of the power relay do the same checking on the PS-ON pin.

Thanks for the reply. I found (5) 5 volt lines. Not sure which is standby as it's not labeled as such.

The first 5 volt line starts at 0 and jumps to 2.68 when the PS clicks.
2nd line stays at 6 volts constantly
3rd jumps from 0 to .7
4th jumps from 0 to .7
5th jumps from 0 to .8

Nothing is labeled as PS-ON. There is an on on-off labeled on the PS but it's opposite on the main is labeled NC. I get no current there..

New symptom, now the power supply will just click when heat is applied, the tv will no longer turn on.

[budm]

Re: Samsung LNS4051DX wont turn on

OK, PS-ON pin is the 'P_ON/OFF pin.
The Standby power supply output is the STBY6.5V pin.
You board is BN44-00134A, right?

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

OK, PS-ON pin is the 'P_ON/OFF pin.
The Standby power supply output is the STBY6.5V pin.
You board is BN44-00134A, right?

Mine is BN44-00134C

[budm]

Re: Samsung LNS4051DX wont turn on

Mine is BN44-00134C

It has the same pin out, it is just REV_C board, it still has the same ON/OFF PIN ON PIN 1 and STBY POWER SUPPLY OUT PUT on pin 2.
http://www.shopjimmy.com/samsung-bn4...wer-supply.htm

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

With no clicking on the power supply.
Pin 1 0 volts
pin 2 6.08

With the power supply clicking after applying heat

Pin 1 2.68
Pin 2 6.08

[budm]

Re: Samsung LNS4051DX wont turn on

With no clicking on the power supply.
Pin 1 0 volts
pin 2 6.08

With the power supply clicking after applying heat

Pin 1 2.68
Pin 2 6.08

so when the relay is clicking the DCV on pin 1 POWER -ON pin is steady at 2.68VDC then?

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

so when the relay is clicking the DCV on pin 1 POWER -ON pin is steady at 2.68VDC then?

Correct. When the PS is clicking, the voltage stays steady at 2.68

[Moreno83]

Re: Samsung LNS4051DX wont turn on

Im thinking a loose contact on the board that with heat gets "connected" again. No cold solder parts?

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

Im thinking a loose contact on the board that with heat gets "connected" again. No cold solder parts?

I looked at the bottom of the board when I replaced the caps and didn't see any.

[Moreno83]

Re: Samsung LNS4051DX wont turn on

Ok try and reflow most of the parts with some new tin on the back of the board. 5 minute job and it might do the trick. Did the same on a samsung last week and its working since then...

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

Ok try and reflow most of the parts with some new tin on the back of the board. 5 minute job and it might do the trick. Did the same on a samsung last week and its working since then...

Ok, touched up the solder joints. Now, the Power supply will turn on and click without applying heat but it will just constantly click.

[jetadm123]

Re: Samsung LNS4051DX wont turn on

What happens if you apply heat to that area?

[Moreno83]

Re: Samsung LNS4051DX wont turn on

Did you fix the tv?

[SHADOW3277]

Re: Samsung LNS4051DX wont turn on

Did you fix the tv?

Yeah, sorry should have posted back but I've been working 70+hours a week and it slipped my mind. After I touched up the solder joints and the power supply would come on without heat but still click, I replaced the caps again thinking one might have went bad after I kept applying heat to them. It worked, the set works perfectly. So it was bad solder joints that was the initial issue, I just exasperated the issue with the caps.

Thanks for the help

[Moreno83]

Re: Samsung LNS4051DX wont turn on

Ok , thanks for the reply! Glad you fixed it.
I had the same issue with my samsung tv , i replaced 2 small fets under a heatsink. I did this because when i applied heat to those 2 fets it turned on. Good chance it was just the solder.....

Greetz