Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

[Jsolts]

Hey guys ,

Long story short tv was working, came back in the room it was completely dead. No power at all.

Replaced the power supply board.

Now it plays they Samsung tune when I plug it in but no change in the screen whatsoever.

When I use my multimeter on the vs testpoint I get 10vdc.
On the va test point I get 3vdc .

I've tried the process of removing the other boards from the power supply and rebooting but same result .

The logic board is blinking 5,2

Please offer any assistance on how to correct my low VS voltage problem

[Jsolts]

Re: Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

Just an update to this as i havent gotten any replies.

I replaced the main input board as well as the logic board and still have the same result.

When i meter the VS-0n i get 1V

Same readings as before on the VS and VA Test points on the power supply board.


Can anyone help point me in the right direction or offer some advice.

Thanks

[ReeceyBurger123]

Re: Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

Poor diagnoses and research on X and Y boards, not willing to help unless you test them first.

[Jsolts]

Re: Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

Sorry about that, I have done a lot of researching, but have not found anything with the same issues. Some have similar problems, yet they get correct voltages on VS and VA, and the similarities end there.

So full disclosure here….

With everything connected, upon power up I get the samsung tune – followed by a few clicks and then nothing. Logic board led reads 5 sec on 2 sec off.
Disconnecting the ymain from the powersupply board yields the same result.
Disconnecting the xmain from the y main (ymain connected to power supply) yields the same result

Disconnecting the ribbon cable from the y main to the logic board results in 1 click, followed by another click and then nothing – no Samsung tune.

Removing the xmain ribbon from the logic results in the Samsung tune and 5on 2 off led light on the logic board.

I have tested the y buffer board for continuity on the connectors to the test point and have found no faults.


I have taken the y board off and ohmmed the transistors
From Left to right in image 1
Transistor 1 - Outside legs -5.81
Left to center – starts around 232 and climbs
Center to right - starts around 232 and climbs
Transistor 2 – ( has combined left and center leg) – Ohmm – 0.L
Transistor 3 - legs – outside legs – 10.
left to center – 1.7
right to center – starts off at 8 cand climbs – settles on 0.L

Opposite side of board –
Left to right
Transistor 1
outside legs- 10
Left to center – 208
Right to center – 197
Transistor 2 – 2 leg – 0.38
Transistor 3 -
outside legs – 10.0
Left to Center - .39
Right to center- .39
Transistor 4 –
outside legs – 10.0
Left to Center - .39
Right to center- .39

Transistor 5 -
outside legs – 10.0
Left to Center – 0.L
Right to center- 0.L
Transistor 6 – 2 leg
left to right- 0.L


X Main from left to right
Transistor 1 - 2 leg – center and left combined
left to right - 1.4

Transistor 2 -
outside legs – 10.0
Left to Center – 1.6
Right to center- 1.6

Transistor 3 -
outside legs – 5
Left to Center – 3.4
Right to center- 3.4

Transistor 4 -
outside legs – 5
Left to Center – 3.4
Right to center- 6.4
Transistor 5 -
outside legs – 10.0
Left to Center – 1.3
Right to center- 1.3

Transistor 6 – 2 leg - center and left combined.
outside legs – 1.3

Other side of board
Left to right -
Transistor 1 – 2 leg - center and left combined.
outside legs – 1.6

Transistor 2 -
outside legs – 10.0
Left to Center – 1.3
Right to center- 1.3
Transistor 3 – 2 leg - center and left combined.
outside legs – starts ar 3.4 and climbs
Transistor 4 -
outside legs – 10.0
Left to Center – 1.4
Right to center- 1.4
There are two other Transistors that are not attached to the heat sinks and they meter out a 220 and climb.


Hopefully this information helps. If you have anything else for me to test to help you help me please let me know.

Thanks

[Jsolts]

Re: Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

So I realized that I did this wrong. I was omming and testing for continuity.
Now that I put the meter into diode mode, I believe I have two blown transistors on the y main.

Can someone confirm this for me, these are my readings.

From Left to right in image 1
Left to center – 1.5
Center to right – 5.9

Transistor 2 – ( has combined left and center leg)
Center/left to right - 4.21

Transistor 3 -
left to center – .OL
right to center – starts off at 1.2 then drops to - .0L

Opposite side of board –
Left to right

Transistor 1
Left to center – 1.9 then drops to – .0L
Right to center – .0L

Transistor 2 – 2 leg – 0.38

Transistor 3 -
Left to Center – 1.6
Right to center- .49

Transistor 4 –
Left to Center – 1.8
Right to center- .49

Transistor 5 -
Left to Center – 1.4
Right to center- .39

Transistor 6 –
left to right- .39

[ReeceyBurger123]

Re: Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

Ok seems like you might have shorted devices. If you put the red probe on vs on the Ysus and Xsus then black to ground what reading do you get ? Make sure you have both boards disconnected from each other. Reply might be slow from me atm but happy new year.

[Jsolts]

Re: Samsung PN51D450A2D - 10 vdc on VS 3vdc on VA

My x feeds the power from the ysus .

When x is disconnected from y I have 10vdc coming from the power supply on the vs wire.

Is that what you meant. ?

I could only find another spot on the board that had vsc. But there was no voltage .