Need advice on next step trouble shooting Samsung PN51D550


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Need advice on next step trouble shooting Samsung PN51D550

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fourholesn1
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Jul 6, 2014, 3:28 PM

Post #1 of 10 (7152 views)
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Need advice on next step trouble shooting Samsung PN51D550	Can't Post

I am trying to repair a Samsung PN51D550 plasma tv. The tv won't power on. I found a good video for testing:
http://www.youtube.com/watch?v=-7zWKY2Hwnc

The Y Buffer board checks ok. Every connection on power supply connector CN801 checks out ok. But when I test PS connector CN802 the first two PS pins check ok but when I test pins 4 and 6, VS control, I get nothing. When I test the VS Test Point I get 11 V but the video says I should get 207V but that it can vary according to the potentiometer, but is 11V still ok? And on the VA Test Point I get zero volts but the video says 60V, again with a potentiometer.

I suspect what I am getting is not right but the video doesn't say what boards could be bad here. When I test CN201 on the main board everything tests ok. The video then talks about the "heartbeat LED" on the logic board. Mine is beating very slowly which the video says indicates a problem with the drive, the Y Main board or Y Sustain board but it doesn't say how to determine which board to replace. But then he disconnects the PS to the X and Y main boards which causes the slow blink just like my tv has. He then says my tv is having a problem with one of the scan boards, either the X or Y main, or it could be a power supply problem.

Based on all this it appears to be an X or Y main board problem but which to buy? Any test I can do to tell? Or could it be a PS board?

flyatyou66
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Jul 6, 2014, 8:11 PM

Post #2 of 10 (7133 views)
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Re: [fourholesn1] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

Is that model number PN51D550 or PN51D550C1F? Need to know
Also when tv on for 1/2 hour with 1 finger touch heat sinks on both y-sus and z-sus boards. They should be warm or a little on hot side.If really hot supect short. Remember if y board is cold z board will also be cold.

fourholesn1
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Jul 6, 2014, 8:32 PM

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Re: [flyatyou66] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

On the sticker on the back I see Model No PN51D550C1F and Model Code PN51D550C1FXZA. I will try the heat sink touch test and let you know. Thanks for the help!

flyatyou66
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Jul 6, 2014, 9:17 PM

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Re: [fourholesn1] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

You don't mention what your tv is doing like, does it power on, do you still have sound, does powerlight come on, does it come on then shut off, does power light blink or your absolutely dead.

fourholesn1
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Jul 8, 2014, 2:11 AM

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Re: [flyatyou66] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

Sorry for the delay in answering, this tv is at my son's house so I have to get him to do these tests, not easy!

So he reports that after power on the red light comes on briefly, maybe flashes some quickly, then goes off. There is no picture or sound. Some clicking is heard but not immediately.

After 30 minutes of power being on the X and Y main board's heat sinks are cold, or room temperature. The PS board heat sinks are slightly warm. I'm not sure which board is the Z board, logic? Or the one with all the connectors?

flyatyou66
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Jul 8, 2014, 9:22 PM

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Re: [fourholesn1] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

The z-sustain board is on right side looking at tv from back.Opposite side from y-sustain board.
The flashing red light when turned on is very important as the number of blinks is a location of problem.(Blinking codes for service repair) If the y-sustain is cold the z sustain is probably cold to.
So lets disconnect the y sustain from the power board.POWER BOARD END NOT Y-SUS END. The flashing red shoul be gone and tv should turn on. If it doesn't hook up y-sus connector and then disconnect z sustain connector end from power board. Again tv should come on.Let me know how this goes.

fourholesn1
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Jul 9, 2014, 9:58 PM

Post #7 of 10 (7061 views)
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Re: [flyatyou66] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

I went over to my son's house today and did this testing. Unplugged the Y sus board and plugged in the tv and got 6 slow blinks, about one per second. No picture or sound. Tried to turn on the tv with the remote and got 4 very fast flashes, all 4 in less than one second. Still no pic or sound

One thing to note is that there is no input connected to the tv so I don't know what sound you would hear but I think you would see some kind of picture.

I then reconnected the Y sus. The Z sus, the similar board to the Y sus, on the right side of the tv, looking from the back, is powered off of the Y sus board so I unplugged the power connector on the Y sus. There is no connector from the PS to the Z sus. The results of this were identical to unplugging the Y sus as described above.

Probably not useful but I also unplugged the logic board and got the same results. I also unplugged the main board, the one with all the connectors, and then got no red light or anything.

What do you think? Any more testing I can do? Thanks for your help!!

flyatyou66
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Jul 10, 2014, 12:15 AM

Post #8 of 10 (7048 views)
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Re: [fourholesn1] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

6 blinks is y-sus problem.So tv did recognize that problem. Earlier you mentioned a problem with cn802.This video will show you how to test these pins and others to help narrow it down problem. Also could you disconnect the z-sus from y-sus board and turn on tv. My mistake for z-sus power supply to psu board. I am thinking it's the z-sus diodes but will see what results you get. Does your heatsink get warm on z-sus?Can you get a dmm and do this test again

http://www.youtube.com/watch?v=-7zWKY2Hwnc

(This post was edited by flyatyou66 on Jul 10, 2014, 12:20 PM)

fourholesn1
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Jul 10, 2014, 3:11 AM

Post #9 of 10 (7041 views)
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Re: [flyatyou66] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

That's the same video I referenced in my original post. So I did test those pins on cn802 as I described in that first post, what else should I do with that? That video is great for showing how to test but it doesn't tell you everything about what to do when you don't get the correct readings.

I did disconnect the z sus power from the y sus board and got the 6 blinks when I powered it on and no picture..

The heat sink does not get warm on z sus.

flyatyou66
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Jul 10, 2014, 6:22 PM

Post #10 of 10 (7034 views)
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Re: [fourholesn1] Need advice on next step trouble shooting Samsung PN51D550 [In reply to]	Can't Post

Woops-- wrong 1.
http://www.youtube.com/watch?v=JjrwTZC5nVg
I went back to the top of discussion, and started to recheck your pin 4 and pin 6 plus 11 volts on vs. After research i found that if 3.3 is not present on power board pin 4-6 it,s the power board because that turns on va plus vs. It looks like you need power board.
On top is youtube i wanted to send you. She refers to smps board which is power board. 1 other thing you should do is take out power board flip it over and check all parts (fets and diodes) that are attached to the heat sinks.These pieces are famous for cracking around these pins. Look for poor solder joints on entire board and parts that don't look good before you order power board.I would also take a close look at capacitors near CN802 connection.

(This post was edited by flyatyou66 on Jul 10, 2014, 8:37 PM)

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