Samsung pn50b550t2fxza

[Digglr]

Hi All!

This TV has a lit power light. When I try to turn it on, it clicks a few times and shuts off. Sometimes a popping sound is heard. any ideas where to start? I can post any pics requested. Thanks in advance!!

[Alastair E]

Re: Samsung pn50b550t2fxza

A pic of the chassis and the PCB boards would be helpful--as well as any labels inside having reference-numbers too....

Have you a digital-multimeter?--Essential for any fault-finding on any TV set....

[Digglr]

Re: Samsung pn50b550t2fxza

Pics attached. If I need to take closer ups, or any others please let me know! I truly appreciate your time!

[Digglr]

Re: Samsung pn50b550t2fxza

Xmain/Xsustain

[Alastair E]

Re: Samsung pn50b550t2fxza

First, try disconnecting that plug near the fuse, from the X-Sus board, and re-try starting set up.
If it comes out of stby, its likely theres a fault on that X board.

If not, try disconnecting the Y-Sus in the same way.

Re-try again....
--Let us know.....

[Digglr]

Re: Samsung pn50b550t2fxza

OK... tried that.. nothing changed each time... either with just X or just Y, or both... clicks...ticks 5 times, led's flash on the pcb.. then nothing.

[tom66]

Re: Samsung pn50b550t2fxza

Do you have a digital multimeter?

[Alastair E]

Re: Samsung pn50b550t2fxza

Ah--OK, right.

On the chassis there should be a small board with ribbon-cables connected to the Y-sus and X-sus.

This board also has the LVDS cable going to the mainboard.
--Without the power connected--disconnect the LVDS cable and look over that small board, there'll be a couple of headers, marked ABCD.
If you short CD (I think) together without that LVDS cable connected, and then apply the power, the set (Should) start and show random test-patterns, if the main panel boards etc are OK...

[tom66]

Re: Samsung pn50b550t2fxza

It is the connector marked 1-2-3-4. You should jumper pins 3-4.

[Digglr]

Re: Samsung pn50b550t2fxza

OK... First, Tom66.. yes, i Have a Fluke multimeter. Second. I did as instructed,(great instructions by the way!) and shorted 3 and 4. When i hit the power button it played a short melody out of the speakers, then the power button flashed 5 times and went out. I tried this a few more times with the same exact outcome.

[Sucher]

Re: Samsung pn50b550t2fxza

Hello. In Samsung TVs there are no error code blinks. In modern Samsung plasma TVs you cannot just unplug your SUS board as microprocessor on CTRL will get the feedback info via I2C bus line that power was disconnected (Vs/Va line) For example if Y sus was to be faulty, CTRL boards sees it and disables PSU board (but you should still get around 200V of Vs voltage for a second before this voltage drops). Even if buffer board is faulty or the PDP, CTRL board can still shut down SUS boards+ Vs/Va lines in PSU.

What you can do is first check if you get Vs/Va voltages ok. If they come up for a second and drop, you can put your ear close to Y sus or Z sus board and listen for a short buzz (confirming SUS board come up for a split of the second.) You could actually use your oscilloscope to capture a subfield waveform for a second but I understand you are not engineer, so you may not have one.

If apart form Vs/Va the rest of the voltages stay on (5V, 12V to motherboard), it means the AV board is working fine.

If you ruled out MB, and power supply is working, I would start looking for a fault from cold resistance checks (check if there's any shorts in Vs line to GND, FET transistors on both SUS boards, check buffer ICs for shorts etc.)
good luck!

Paul

[Digglr]

Re: Samsung pn50b550t2fxza

Thank you for your input Sucher. No, I'm definitely not an engineer. I DO have a oscilloscope, but haven't used it since my Tech school days years ago. If you can dumb down a few things... like what is Vs/Va voltage? Thank you!!

[Digglr]

Re: Samsung pn50b550t2fxza

OK... I did a little research, and found out how to test Vs and Va. Only problem is.. the voltage spikes up when i turn it on, but shuts down right away. I could only get a reading of 20.6V on either, but then it clicked off and decreased to 0.

[Digglr]

Re: Samsung pn50b550t2fxza

Also... if I unplug ALL other connections but the power to the board, should the Vs and Va output be according to specs?

[Digglr]

Re: Samsung pn50b550t2fxza

Anyone?

[Alastair E]

Re: Samsung pn50b550t2fxza

Also... if I unplug ALL other connections but the power to the board, should the Vs and Va output be according to specs?

No--You'll only get the 5V stby supply--there's nothing connected to PSU--to tell it to turn on.....

There's summit upsetting the control-board, summit amiss on either the Y-SUS or X-SUS board, a short or other issue, maybe even a buffer short or fet fault....

[Digglr]

Re: Samsung pn50b550t2fxza

No--You'll only get the 5V stby supply--there's nothing connected to PSU--to tell it to turn on.....

There's summit upsetting the control-board, summit amiss on either the Y-SUS or X-SUS board, a short or other issue, maybe even a buffer short or fet fault....

Any other diagnostic work I can do to curtail it to which board?

[Digglr]

Re: Samsung pn50b550t2fxza

Anyone?

[Alastair E]

Re: Samsung pn50b550t2fxza

Unfortunaterly--not that I can think of. Its a case of checking the diodes/mosfets/IGBT's on each board.

Makers would recommend replacing Y-SUS and Z-SUS as a pair, so not much help from their quarter...

Only thing you could try is pull the buffer-board/s and re-try firing it up....

[Digglr]

Re: Samsung pn50b550t2fxza

From what I'm reading around the web.. the most common fail on these are the Ymain/sustain and Y buffer?