Samsung PS50A656T1F clicking

[Andyd1970]

Hi Guys,

Just taken in a Samsung PS50A656T1F, you give it power and you hear the PSU click to switch on, most of the time it does not come on and occasionally it does switch on and you can watch it.

I have just been trying it and it has switched on 5 times no problem, I cannot see an bulging or leaking caps on the PSU.

Any ideas

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

Check if PSU has 7815 regulator (common fault solder joints)
Also, check the two TO220 transistors (on the primary side in the smaller of the two LLC converters) on the heatsink for bad solder (veeery common)
It's little hard to see, which PSU it is, but I think it's the one.

[Andyd1970]

Re: Samsung PS50A656T1F clicking

Hi, Thank you for the info, please see pic of the PSU, can you please help with the location of the components you mentioned.

The PSU number is BN44-00222A, 20080112, WF3.5 REV1.0

Thank you

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

See areas within red boxes

[Locutor13]

Re: Samsung PS50A656T1F clicking

Hi, I was experiencing something similar with the same PSU. It kept clicking without turning-on, the problem was a cracked solder joint of one of the legs of one of the black relays. You will find those relays just above the main fuse. Also you can check the solder joints in that area, it looks like that area gets really hot.

In my case a reflow of that joint solder brought my PSU back to life.

[Andyd1970]

Re: Samsung PS50A656T1F clicking

Hi,

I did the first reflows as suggested by PowerAmpFreak and it seemed to be OK, but I left it on for about 30 minutes, powered it down by the standby button on the front of the TV. I was just repairing a laptop and the PSU in the TV was just clicking all by its self! how spooky.

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

Hi,

I did the first reflows as suggested by PowerAmpFreak and it seemed to be OK, but I left it on for about 30 minutes, powered it down by the standby button on the front of the TV. I was just repairing a laptop and the PSU in the TV was just clicking all by its self! how spooky.

Keep on searching for more bad joints...

[Andyd1970]

Re: Samsung PS50A656T1F clicking

Hi, I have reflowed the two relay in bottom left, also scanned PCB and reflowed most of the components but nothing was obviously dry. I had it running for an hour and I heard it start clicking on its own so can only assume it powered its self down?

I left it a while and tried to power it up again and the relay clicks around 5 times ish and them stops and if you touch standby button on front nothing happens.

Help!

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

Then it sounds more like the mainboard is shutting off the PSU.
Hook up a meter to the PS_ON signal and see.

[Andyd1970]

Re: Samsung PS50A656T1F clicking

OK,

Just measured it at the PSU end and it switches between 0.660v to 3.475v.

Am I right in saying that is should be 5v?

Andy

[Andyd1970]

Re: Samsung PS50A656T1F clicking

I have checked over all other PCB's and cannot see any damaged components, I have also given it a clean up as it was pretty dusty and fluffy inside.

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

As the PSU starts to click you can see the PS_ON is syncronized to clicking?
In that case - mainboard shuts it off.

[budm]

Re: Samsung PS50A656T1F clicking

Are you saying the 5V STBY is going up and down?
You should check the two small startup-running, filter caps (4 small LYTICS caps) next to that TO-220 Power MOSFET (in red box) for that standby power supply.
And do not touch any heat sinks since some of then will be have line voltage on it.

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

The measurement was meant to be on the PS_ON signal. (Not +5V STBY)
But of course, first you must have +5V STBY to be able to switch on the rest.

[Andyd1970]

Re: Samsung PS50A656T1F clicking

Hi I did measure it on the PS_ON pin on the PSU. I will do the other measurements suggested by BUDM and get back to you.

[Andyd1970]

Re: Samsung PS50A656T1F clicking

Hi BUDM, How do I measure the caps as you cannot get to the legs as under the PCB?

[budm]

Re: Samsung PS50A656T1F clicking

You need to remove the caps and check the capacitance and the ESR.
Try heating that area with hair dryer to see if the 5VSTBY becomes stable, it it does then I would just replace the caps.

[Andyd1970]

Re: Samsung PS50A656T1F clicking

OK great I have a ESR meter

[PowerAmpFreak]

Re: Samsung PS50A656T1F clicking

You are talking about different things here.
Andy measured that mainboard cycles the PSU by PS_ON.
He have not (yet) verified if +5V STBY is stable or not. Would be first thing.
Based on your findings I would focus more on diagnosing the mainboard or perhaps jumping the PSU manually on PS_ON to see if it stays on.

[budm]

Re: Samsung PS50A656T1F clicking

You are talking about different things here.
Andy measured that mainboard cycles the PSU by PS_ON.
He have not (yet) verified if +5V STBY is stable or not. Would be first thing.
Based on your findings I would focus more on diagnosing the mainboard or perhaps jumping the PSU manually on PS_ON to see if it stays on.

Ahh, I read post 10 wrong, now I see that he is referring to the PS_ON not the 5V line.

"Just measured it at the PSU end and it switches between 0.660v to 3.475v.

Am I right in saying that is should be 5v?

Andy"