Samsung Plasma PN50A400C2DXZA

[stephenhartley]

Hello,

I recently received this 50" Samsung Plasma TV PN50A400C2DXZA for free. Currently, when I plugin the device relays clicks on then off. Pressing the power button gives me the Samsung power on sound, the TV primes then glows steadily. Audio and side panel buttons function. I can see a flashing LED on the LJ41-05309A Logic-Main Board. I have done the 3-4 jumper test on the main board with no patterns being displayed on the screen.

Both the Y-SUS and X-Main make a slight humming sound and seemingly get warm. I understand that a digital micrometer (DMM) is really a requirement to accurately diagnose where the fault might lie; however, I was wondering if there was anything I could without purchasing a DMM?

[randtek]

Re: Samsung Plasma PN50A400C2DXZA

Not really. The parts that will cause your symptom are far more expensive than a hobbyist grade DMM. Without being able to test voltages on a plasma, you risk spending a lot of money guessing on parts. It would be wiser to buy a cheap DMM than to just start throwing parts at the thing, hoping you luck into the right one. (In my opinion)

[tom66]

Re: Samsung Plasma PN50A400C2DXZA

Yes, you will need a good DMM on any TV repair.

To do the 3-4 jumper test you must remove the LVDS cable from the main board. This cable goes to the control board.

If the screen primes, it is very likely a main board issue.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

To be clear, what is meant by the priming of the screen?

My current understanding is that the screen glows quickly, goes out, then comes back on with a steady glow. Is this correct?

[tom66]

Re: Samsung Plasma PN50A400C2DXZA

Priming is the continuous, uninterrupted glowing of the screen. On newer plasmas it can be very faint, due to high contrast ratio.

When the panel first turns on the control board will initialise it and erase any previous images or built up charge (image retention.) This may cause some flickering when first turned on and is completely normal. I've noticed Panasonic plasmas are the most discrete about this -- the screen only lightens slightly, then dims down, when first turned on, on an LG/Samsung you tend to see a few light flickers and some sparkling pixels.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

Ah okay. So the TV flickers then is primed (the glowing).

With the LVDS removed from the main board and pins 3 & 4 jumped on the control board, no test patterns are generated on the panel (still primed)

[tom66]

Re: Samsung Plasma PN50A400C2DXZA

You may have a bad control board then. Does the LED blink five times then pause for two seconds repeatedly, or is the blinking steady?

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

When I turn on the TV, LED1 lights up solid for like 1 second, while LED2 flashes steadily for as long as the TV is on.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

Here is a picture of the rear of the TV in question as well as the logic/control board.

[tom66]

Re: Samsung Plasma PN50A400C2DXZA

I did a little research and it might be pins 1-2 for this model to do the test patterns.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

No test patterns on any pin configuration.

[tom66]

Re: Samsung Plasma PN50A400C2DXZA

OK then, one more thing to check. Along the bottom of the plasma panel there are two or three small boards. There should be a fuse, a little like this, on one:
http://www.newark.com/productimages/...rd/4556386.jpg

You will need a DMM: Measure the voltage on both ends. If it's near 0V on one end, the fuse may be failed. There is a chance this means the plasma panel is defective and repairs beyond replacing the fuse should not be attempted. If the fuse is good, it is probably the control board that is faulty. We had a user on this forum have that fuse blow, they replaced it and it worked fine again. Same symptoms.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

Wild this DMM by craftsman be suitable to correctly diagnose the fault with my TV?

the DMM in question

[Alastair E]

Re: Samsung Plasma PN50A400C2DXZA

Wild this DMM by craftsman be suitable to correctly diagnose the fault with my TV?

the DMM in question

Yes--That'll do.

Its a little basic on the Ohms functions, but will be fine for what you need

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

Okay. I purchased the aforementioned DMM. Where do I begin? I have never used a DMM before.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

That small fuse doesn't cause the meter to beep, reads "1". All other fuses are okay, DMM beeps and I get a "0" reading.

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

Also, what would cause this fuse to blow? Y-SUS Failure?

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

So, I decided to inspect those buffer boards closer, in particular, one stood out: PCB number LJ41-05512A has something that looked as though it could be burned, it's almost as if the solder is gone. Anyway, here are some photos:

[stephenhartley]

Re: Samsung Plasma PN50A400C2DXZA

Bumping for opinions, advice. Thank you!

[LDSisHere]

Re: Samsung Plasma PN50A400C2DXZA

It looks like the capacitor burned up. You should check the resistance of the capacitor as it may be shorted. If your fuse is before this device, it could be what caused it to blow.