Samsung Plasma PN59D550C1FXZA Doesn't Power ON

[karthur]

I picked this up at a yard sale and the owner knew nothing about it. Just knew that it didn't work. I get it home and sure enough it doesn't come on. Here is what I do see/hear.

When its first plugged in, I can hear a click. It sounds like its from the power board. There is a red light on the front by the control panel that blinks 6 times. When I touch one any of the buttons on the front panel the red light will flash. I pulled off the back cover and looked at all the board. Nothing out of the ordinary. Nothing looks burned or damaged. On the power board (BN44-00445A), there are connectors CN801, CN802 and CN804. Below is the readings from these connections with it plugged into 120VAC.

Any help to figure out why it will not power on would be much appreciated.

CN801
1. PS_ON - 0.17VDC
2. STBY - 5.3VDC
3. GND - 0
4. 15v - 15VDC
5. GND - 0
6. GND - 0
7. D5.3v - 5.3VDC
8. D5.3v - 5.3 VDC
9. GND - 0
10. 15v - 15VDC
12 . D5.3V - 5.3VDC

CN802
VS_ON - 0
PS_ON - 0
VS_OCN - 0
GND - 0
D5.3v - 5.3VDC
D5.3v - 5.3VDC

CN804
Vs - 0.38 VDC
15v - 15VDC
Va - 0VDC

[karthur]

Although mine is a BN44-00445A, here is a schematic I found for the BN44-00445C. Not sure how similar they are.

[karthur]

I did more checking on the power board. When I plug in the 120v power, the PS_ON goes to 0.17vdc. Touching the power on/off button on the front panel doesn't cause the value to change. If I then unplug the power cord, the voltage increase to 2.96VDC. From what I have read, PS_ON >3 vdc = OFF and PS_ON<1vdc = ON.

Its confusing to me that the PS_ON is .17vdc when I first plug it in. Shouldn't that be >3vdc until the power button is touched on the front panel. Does that mean the power board is the problem?

[R_J]

PS_ON should be high (3v) to turn on QT409 transistor, normally the main board will hold that pin low when you unplug the power cord, the main board logic could temporarily show that voltage go high.
I suspect there is problems on the Y-sus or Z-sus boards, likely shorted mosfets. with the tv unplugged, check the resistance across the VS and ground on the power supply, there may be a short or low resistance
Search the model ( PN59D550 ) there are other threads on this model

[tvtimmy]

Change the 3 blue capacitors on the y-main (circled in red). Then try it. Bye the way, they are 10uf 50v each.

[karthur]

PS_ON should be high (3v) to turn on QT409 transistor, normally the main board will hold that pin low when you unplug the power cord, the main board logic could temporarily show that voltage go high.
I suspect there is problems on the Y-sus or Z-sus boards, likely shorted mosfets. with the tv unplugged, check the resistance across the VS and ground on the power supply, there may be a short or low resistance
Search the model ( PN59D550 ) there are other threads on this model

I ohmed between Vs and ground. Goes up and down between 5k and 460k ohms. This is with all the connectors on the PS board plugged in.

[karthur]

Change the 3 blue capacitors on the y-main (circled in red). Then try it. Bye the way, they are 10uf 50v each.

Thanks for that. I have located those components. Will try to get them off the board tonight. I have some old boards I might could scavenge some components.

Kirk

[karthur]

A few more observations:
1. From what I have found from other YT videos, the 5 blinks of the front red LED is normal. The should mean the TV is ON.
2. When I plug in the power, there is a green led on the board below the power board that blinks. 5 seconds on - 1 second off.
3. If I unplug the Y Sustain board and then plug in the power, the Vs starts at 220VDC then slowly starts to fall. With the Y Sustain board connected, the Vs starts at 1.0vdc, then falls quickly to 038vdc.

[R_J]

You likely have shorted mosfets on the Y-sus board, there may be other faulty components as well

[karthur]

Change the 3 blue capacitors on the y-main (circled in red). Then try it. Bye the way, they are 10uf 50v each.

Could I replace those with these type capacitors? These are 10uf, 50v also. If not, I would have to order the disc type.

[tvtimmy]

You can do that. Make sure you put the positive sides where they have to go.

[karthur]

You can do that. Make sure you put the positive sides where they have to go.

I got those three caps off the board. All three measure 9uf. I will order the correct ones to go back, that way will will not be questionable. Plus I am not so sure the legs on the ones I have are long enough.

I checked all the MOFSETs on this board. The only one that I think is shorted is the D5014 (#SF10S600D2). That is, if I checked it right.

[tvtimmy]

That is a diode. Both legs are the same. Measure the ground tab and each leg in diode mode.

[karthur]

That is a diode. Both legs are the same. Measure the ground tab and each leg in diode mode.

Bear with me... I am new to checking these components. I found the cutsheet on the SF10S600D2 Diode. Below is the reading I get on all the legs. Doesnt matter what leg I put the probes on, I get 0.00 on my meter in diode mode. I see two of these diodes on my board (D5014 and D5014). Both of them measure the same way. Could both of these be bad or is it not possible to check them in-circuit?

If I change to Ohms, I get 0.2ohms between 1 and 2 and also between 3 and 4. Again, same readings on D5014 and D5015.

[karthur]

Am I checking that correctly? Since this is a diode, its seems that between 1-2 and 3-4 should read as open in one direction, but closed in the opposite direction.

[R_J]

I believe that dual diode is across other components on that board, so it is likely some of the mosfets are shorted. maybe Q5002, Q5003 etc.
There is an 8 pin plug near the large green electrolytics, on the board is a legend of the pinout. check the resistance between VS (7or8) and ground (3or5)

[karthur]

I believe that dual diode is across other components on that board, so it is likely some of the mosfets are shorted. maybe Q5002, Q5003 etc.
There is an 8 pin plug near the large green electrolytics, on the board is a legend of the pinout. check the resistance between VS (7or8) and ground (3or5)

The 8 pin connector is CN5027. Checking between VS (pin7 or 8) and GND (Pin 4 or 5) reads 120k ohms. This is not a steady reading but gradually increasing.

There are several of those under the large cooling fins. Q5001, Q5002, Q5003, Q5004, Q5005, Q5007, Q5008, Q5010, Q5020, Q5021, Q5022. When I check those with my meter in diode mode, with (+)Drain and (-) Source I get anywhere from 0.002 to .5vdc. not of them read 0L. IS this because they are shorted or because they cant be tested on the board?

[R_J]

Many of those components are in parallel so it is likely only one or two are shorted, you would need to remove them one at a time to find the bad ones, if a mosfet is bad, it is likely the drive components could also be damaged

[karthur]

I went ahead and ordered a new replacement board. Plugged it in and TV works great now. If I get a chance next week I am going to pull out some of those Moffett and see how they read off the board.

I found a replacement new board at ShopJimmy for $40. I thought that was very reasonable.