Samsung PN50b550T2FXZA Big disappointment

[R1racer]

After i successfully got the Set to work for 2 weeks tonight outa all nights big disappointment when the SMPS clicked out of no where and decided to cut off Like it lost it's power , 1 minute latter it powered back up by it self ( Thought of bad caps )..20 minute latter set is totally dead , it's been 2 hours with No standby . i did not bother yet to open it up

History ..When the set died 2 month ago it was the same symptoms , After several days of trouble shooting i replaced the following :

Main board .supposedly Brand new from Samsung parts supplier Main bad card

Y Main due to loss of pic during trouble shooting

Logic board to rule it out


TV Set worked like a clock work for solid 2 weeks with amazing Pic .All i can say is

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

Disconnected about all boards from SMPS ( Y main , X Main , Logic ) Except the main board connected to SMPS still no Standby .

Now i checked all SMPS fuses and nothing wrong with them, Caps do not appear blown .

I connected every thing back and disconnected the cable going to main board and used a jumper from PS-on to ground o test logic and SMPS but no luck ..


Does it sound like SMPS or Logic board , I have good known logic board

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

[budwich]

Re: Samsung PN50b550T2FXZA Big disappointment

of course you have verified all the voltages as indicated?

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

last pic right before the solder direction arrow is a legend with the voltages printed on it each connector has one what voltages are you getting? I think you have a power supply problem. if main was bad you still would have stby.

[ReeceyBurger123]

Re: Samsung PN50b550T2FXZA Big disappointment

Check for cold solder joints ? Also fuses good ?

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

When set goes into total blackout i have no way of testing voltage.

I checked the SMPS for any solder issue and couldn't find any thing that will jump at me so i installed back again . I do believe there is something is wrong with the HDMI 1 port
as as soon i plug the HDMI cord coming from the cable box to it the set loose it's power and goes into black out so thankfully it came back withing a minute or so so i Moved the HDMI cord to #2 and i was able to get to work ..

But i was not totally convinced so i took it farther and moved the cord back to #1 and shit it did it again and now the set in a blackout mode ... I can live with 1 or 2 HDMI ports are bad if that's all to it ...


Now i am in the hurry and wait stage for the set to decide to clear it self from protected mode unless some of you guys know how i can force it to clear

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

Set still in blackout mode no power present .I tried to unplug every thing one at a time in hope for power to come back but no luck .. My observation is that the power comes back on when ever it likes ...

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

try heating the power board with a hairdryer in spots, if no luck try freezing it with component cooler or a can of compressed air turned upside down so not to get liquid on it.

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

try heating the power board with a hairdryer in spots, if no luck try freezing it with component cooler or a can of compressed air turned upside down so not to get liquid on it.

Should i be doing this while the board mounted in place or out the set

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

you couldn't try it to see if it worked if it was out of the set. I am guessing maybe the pfc cap high esr. if so the hairdryer will tell

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

Went over the caps with the hair dryer .. I did not go crazy thought , I made sure to keep fair distance .. No change total blackouts .

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

do you have a digital mm with diode test? on the black heatsink right behind the largest cap there are a pair of diodes three legs one is common cathode one common anode, check them also look for bad solder joints here. I had one I had to trace. I have the schematics for that power board. the pfc cap would have been one of the smaller caps. the off and on makes me think it may be a cap or bad solder joint.

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

do you have a digital mm with diode test? on the black heatsink right behind the largest cap there are a pair of diodes three legs one is common cathode one common anode, check them also look for bad solder joints here. I had one I had to trace. I have the schematics for that power board. the pfc cap would have been one of the smaller caps. the off and on makes me think it may be a cap or bad solder joint.

I will pull the PS and look closely and report ... I hate to give up on this thing . I got so far now with it. it was working perfect for 2 weeks and i am in love with PIC quality compare to others currently in the market

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

you have to have an intermittent connection somewhere solid state components don't come and go. esr could cause it you may want to try cooling the power board cold contracts heat expands. after it cools it seems to work? check all the heatsinked components while you have it out.

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

diode test result am seeing some .568 and .988 on 2 of the 3 legs per each Diode or close to it ... Not know what values am assuming this is ok .

And i agree with the you on the intermittent connection but nothing jumping right at me .I am cooling the board now for and will see

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

Ok so as crazy as this sound ... I decide to get the SMPS chilled inside the freezer next to the Ice cream for about 90-120 second , Pulled out i installed it back and power is back on and is working like a champ ...

No telling how long it is going to be on for , However now we know heat doesn't work only cold does it .

I have my HDMI cord going to HDMI #2 , I am going to monitor

[R1racer]

Re: Samsung PN50b550T2FXZA Big disappointment

11 minute latter and it went dead ..Something in the Power supply causing it for sure and cooling it cure the problem for so short period

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

probably a cold solder joint, try touching up all the heatsinked components with solder, you need to wait on the caps to discharge first though. I use a weller grounded tip and it has been known to arc from time to time. you have a bad solder joint somewhere, caps usually respond to warming the cool would cause the solder to contract and therefore work till it expands from heating.

[awyatt2]

Re: Samsung PN50b550T2FXZA Big disappointment

can you get a good pic of the underside of the power supply? I may be able to see something there.