Samsung plasma pn50a550s1fxza

[audiodreamer]

Good morning all! It is good to have found this forum. Like most things I own if I can fix it myself I will.

I got this tv around 2008-09. After about 2 years had to have the main board replaced.

Now the tv just shut down and started clicking. The red led on front along with it.
I suspect smps board. I unplugged all other boards from it and checked va and vs voltage. I had none.

I have had some basic electronics training in the military and feel confident that I can fix down to the component however like I said basic. I found on forum something about a bad cap on back of board but how does one confirm? Where do I start checking and for what voltages etc.?

I found a schematic but the and printed it but the print was so small I could not see.

Another thing I did was plug in each board by itself until I came to one that created the relay clicking on smps board. The main board made the clicking resume. But with no va and vs voltage then I don't think it is that board.

Any help would be appreciated.
Thanks Mike G.

[Alastair E]

Re: Samsung plasma pn50a550s1fxza

Is this the big heavy early first gen FHD set....?

Ive had caps and voltage-regs fail on the PSU, the 5V reg near the STDBY supply gen stage can cause it to go dead, as well as the smaller voltage caps on its O/P's....

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

Oh yes it's heavy. Appearance wise all of the caps that look like what call normal capacitor look to be fine. What about this 5v reg. Where exactly is it located? I presume it will be obvious as far as diagnosing. Also at vg it is labeled to have 15volts. It has none.

Thanks

[Alastair E]

Re: Samsung plasma pn50a550s1fxza

There's no 15V or any other supply--Until the Mainboard turns the PSU on.

It does this by Grounding the PS-On pin. Then there'll be 15V and the main 5V supply, but No Va or Vs.

For that, the Mainboard/control-board applies 5V to the Vs on pin of PSU....

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

Let me make sure I follow. The main board which gets its power from the smps board and in turn provides the 5 volts back to the smps board?

Is the tv in an on or off state for that to happen?

If the relay on smps and by feel I t seems to be the top one is continually clicking where does one start to look for problem?

[ReeceyBurger123]

Re: Samsung plasma pn50a550s1fxza

With the Tv on, the Psu relays require the motherboard to apply 5v which is generated from the standby rail for the gates on them to open and run the rest of the Psu. Can you upload some images of the boards please ?

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

Hello and good morning! I hope these pictures are ok. If there arany that need to be retaken or from different vantage point please let me know. I hope I got what would seem important.

Thanks for everyone's time

Mike G

[rccrasher65]

Re: Samsung plasma pn50a550s1fxza

Check for cold solder joints on SMPS, mine had a ton of them. Mostly the components on the heat sinks. The cap is C102 on back of main board, sometimes marked, sometimes not. there are threads on here for location.

[flocko]

Re: Samsung plasma pn50a550s1fxza

This looks to be a BN44-00222 power board? if this is the case it has a green LED on the small daughter board at the bottom right of the board, when in stand-by the green LED should be on and steady. if when you try to turn on the supply with remote and the relays keep clicking the green LED will flash a blink code. You will see screen printed a list at the side of the board telling you what the code is? There is also a set way to bring the board to life out of the set to test it. But give us the LED blink code first

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

As soon as I plug the tv in relay starts clicking. The red standby light blinks on and off with the clicking of relay. The green led light stays on continuous.

[ReeceyBurger123]

Re: Samsung plasma pn50a550s1fxza

Right have you checked the Pson signal ?

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

I wish this was easy for me. I am an electrician by trade. I am pretty handy when it comes to working on my auto's. I am sorry to say that my basic electronics are not getting me very far.

Ps on signal? Where exactly and what am I checking for?

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

At the connector on smps that goes to main board there are 2 rows of pins. between gnd-stby and stby I have 5.2 volts. That harness was unplugged.

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

With all harnesses plugged in each time relay clicks I get 5V then 0V cycling. TV is plugged in only.

[flocko]

Re: Samsung plasma pn50a550s1fxza

Are you saying the st-by voltage is swinging from 5v -0v? I think you need to pull the power board from the set and test it on its own.I am thinking this to be a BN44-00222 power board? First with only the main supply to the board check for stby voltage(5.0v) Then on the right hand bottom corner of the board find jumper JP153 connect a wire to this jumper. If you have the 5v stby you will also have the green LED I told you about before .with the other end of the wire on JP153 put this to a ground point ( you will see one just up on the right side of the board ) with this grounded you should hear the relay click and all voltages come up apart from the VS. If not the the relay will click a few times then stop with the green LED flashing its code. please let us know if it works or what the flash code is or if you dont have a steady stby

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

I took a jumper with an alligator clip at both ends and hooked one end to jumper 153 and the other two ground.

Before doing this I isolated board. Only 120v applied. I had stby volts of 5.2 and green LED. with jumper in place absolutely nothing happened. green led stayed on and no relays active.

[flocko]

Re: Samsung plasma pn50a550s1fxza

Sorry I see the problem its JP154 you need please try that again. you ground on the power board the same as in photos ?then you have a problem with the power board , i would check what the stby voltage is doing when you ground the jumper first as this going low could be your problem

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

With jumper in place relay clicks once, and green led light stays constant as well as stby voltage. That is the only voltage present.

[flocko]

Re: Samsung plasma pn50a550s1fxza

you should be holding the jumper to ground not just flashing it. When the relay clicks in you should get the 5.3V /12v / Ve +Va the only one that will no come will be the Vs

[audiodreamer]

Re: Samsung plasma pn50a550s1fxza

It is clamped down and I am not getting any of those voltages.