Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

[super98lsc]

Hello everyone, this is my first post here but I am not new to electronics at all. I have a 4 year old Samsung 64" Plasma PN64D550C1FXZA that began turning itself off after a short period of time. It shuts down, restarts itself 2,3 times then goes completely dead requiring a power cord plug/unplug to reset it. Here is what I have done so far. The picture has no issues and looks great. No physical damage.

VA 217v on spec
VS 55.2v on spec
Vscan -197v on spec
VE/VB 93v on spec
Pwr ON Voltage 3.24v on spec
Standby 5.4v on spec

When the shutdown occurs the 3.24v Pwr ON Signal to PIN 5 of CN802 goes to ZERO. So it appears to me the Logic board is shutting it down due to an error... which I suspected was in the drives. (Y-SUS)

The unit powers up with the main board disconnected and the Logic board in test pattern mode. Pin 1 on CN801 shorted to ground and LVD cable removed from the input board. It runs for the same amount of time then shuts down. 1-4 minutes max.

I pulled the power supply board and found several bad solder joints, including one by the power factor correction section that likely only ever worked because of the silicone holding the resistor in place. I pulled nearly every component on the board, tested all the caps on my LCR meter, ran a curve tracer on all the MOSFETS and checked every single diode and resistor. Not one thing on that board is out of spec that I can find. Although I did not change the IC's on it. Va/Vs remain on target then go to ZERO when the shutdown occurs. I do not observe any voltage drift.

I replaced the following with tested known good replacements:

• Y-Sustain/Main - found the ribbon cable from the Y-Sus to X-main was burned at the Y-Main connection so I replaced it with a new cable at the same time. It sure appears some serious heat/current was being fed over to that X-main to make the white molex connector burned brown and cracked, also the ribbon was burned dark brown about 12-13" from that same pin.
  
• X-Main
• Logic Board
• Input/Main Board
• Every cable inside the set with a new set of cables (new in box)

The Y Scan Drives all test fine with the VOM aka none show or appear shorted. None of the IC's are running hot and the picture is perfectly clear and normal 100% of the screen.

At this point the only things I have not pulled are the X drives at the bottom of the screen.


Thanks in advance for any assistance this one has me a bit perplexed.

[Nick's Tvs]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

This model is known to have cracked solder joints on the power supply. The middle heat sink specifically gets cracked joints on the components screwed into it. I would reflow those along with the components in near proximity more specifically the blue capacitors to the right of the heat sink as those have legs that share pads with these high heat components and because of it are also prone to having cracked solder joints.

[ReeceyBurger123]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

this model is known to have cracked solder joints on the power supply. The middle heat sink specifically gets cracked joints on the components screwed into it. I would reflow those along with the components in near proximity more specifically the blue capacitors to the right of the heat sink as those have legs that share pads with these high heat components and because of it are also prone to having cracked solder joints.

+1

[super98lsc]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

I appreciate the input, however as mentioned in my original post I had already pulled, tested, and re-soldered every component on the board. Agreed the factory solder joints were garbage. All of the components tested perfect, caps well within 20% tolerance and none with high ESR. The supply is getting a shutdown signal FROM THE LOGIC board. If I jump the power supply on the bench it will run for hours on end.

I have a spare supply board that is known good and will try it this afternoon if the new X-Buffer board arrives today. (right side board that connects to the x-main)

What I really want to know is there a way to test the lower buffer boards at the bottom of the screen?
Specifically PCB LJ41-09457A, LJ41-09458A, LJ41-09459A

[Alastair E]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

Unlikely to be bottom buffer address boards or COF chips/panel causing this.

Much more likely--The Logic-board is Detecting a fault on the Y or X sus boards--and going into protect, then shutting PSU down.

[paul85]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

I just picked up one of these off a craigslist post today and will open it up tonight or tomorrow to assess damage. Owner said he was watching TV and it popped and all power went out. He said it clicks which sounds like the power board. Hoping its simple like bad solder joints. There's not much info out on the web about problems with these devices other than this thread. I'm a total noob, but have repaired a couple 42 inch samsung plasmas and a couple panasonic plasmas in the past so I'm hoping for success with this unit. It's very big and very heavy.

[paul85]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

Seems I have a short in my power supply. The main fuse was blown so I went to radio shack and bought another 10 amp fuse. They didn't have the correct length, so I made it work. Plugged it in and boom, sparks flew and I circled the small burned dot on the board it made. Sparks flew from the square transformer? right to the top right of the dot on the board.



Looks like qp802, qp804, and dp802 are probaby suspect (mosfets) Unfortunately, I will have to place an order with digikey or mouser to get some parts.

This video has been a ton of help.
http://worldwide.chat/Samsung_Plasma...tNRiZwN8.video

[paul85]

Re: Samsung Plasma- Shutdown Failure- PN64D550C1FXZA

Replaced the QS804 and QS802 Fets. Also replaced the fuse and QP802 and QP804 after QS804 tested bad. Now the power supply turns on but clicks like a relay is cycling.

Testing with my dmm, on CN801 I get 4.28 volts on pin1, 5.29 volts on pin2. With pins 1 and 3 jumpered on with a 470 ohm resistor, when I check the 3 large PFC caps, I'm only getting 160 volts which is too low. Should be around 386 VDC, not 160. What else should I be checking?