Samsung PS42B450 Y Main

[thestigp11gt]

Hi, I have recently been given a Samsung plasma TV, which was faulty. After diagnosing the TV it appeared that the Y Main board was at fault. I ordered a brand new Y Main Board, fitted it, switched the TV on and a nice picture appeared, after about 5 minutes of the TV being on, the screen started to go darker and darker and then the TV switched off, and the same problem it initially had started again, The clicking on and off sound.

Could this just be a faulty part also and bad luck?

[capkid]

Re: Samsung PS42B450 Y Main

Have you used a multimeter to check your X-main for faulty components? Also, I'd check the Y-main again without powering on the set. It's possible that your Y-main is still good, but you could possibly ruin it if you turn on the TV again. Unless your chassis is somehow different from what's shown in the attached pic, the X-main appears to be receiving power from the Y-main.

[tom66]

Re: Samsung PS42B450 Y Main

On these sets, the X-main chains power from the Y-main, but also combines energy recovery.

Therefore, if you cannot test both boards and find they are OK, you should replace both at the same time, and also should consider the buffer, though on these sets the buffer rarely fails when the Y-main goes bad.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

Thankyou so much for the replies. When I disconnect the X Main, the TV powers up, as you can hear the start up tone. and powers down with the command from the remote control. I am told that a faulty X Buffer can cause the X Main to pop, and I am wondering if this is the case.

Also that PS42B450 looks different to the Samsung TV I have

[tom66]

Re: Samsung PS42B450 Y Main

There is no such thing as an X buffer with regards to the X-main; the little board attached to it can be called an X buffer but not really as it's just a glorified connector assembly.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

So what is the name of the long board on the left hand side of the TV:

[tom66]

Re: Samsung PS42B450 Y Main

Y-buffer, connected to the Y-main.

[capkid]

Re: Samsung PS42B450 Y Main

It's not applicable to this Samsung, but some of them do have X-buffers.

[tom66]

Re: Samsung PS42B450 Y Main

On some, I have seen a few components on them, but most are just glorified connector assemblies.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

Sorry guys, I had completely mistyped one of my replies.

I meant to say that I was told that the Y buffer should be replaced when the Y main is replaced. Can the Y buffer cause Y main failure?

If I disconnect the Y Main, then the TV powers up, and you can hear the start-up tone, when the Y main is then reconnected then the TV just clicks.

How would I test each of the boards to verify if they are dead or not?

[tom66]

Re: Samsung PS42B450 Y Main

Yes, a bad Y buffer can kill the Y main.

You can test the buffer:
http://www.youtube.com/watch?v=51SZsfH60EY

[thestigp11gt]

Re: Samsung PS42B450 Y Main

Done a test as shown on that video, and it appears that the Y Buffer appears to be OK.

[tom66]

Re: Samsung PS42B450 Y Main

There is one more test I didn't feature in the video, but it involves testing from the sus OUT to the Vad out pins, if you post a picture of your buffer I will highlight the test to be done.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

I have put up both a picture of the Y Main and Y Buffer

How would I go about testing the Y Main to see if it is faulty also?

[tom66]

Re: Samsung PS42B450 Y Main

Here is where to test; use diode mode on your meter. Try both ways, not just as indicated.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

I am getting a reading of ~.900 (give or take a few values) when Positive probe is on Y main connector. No beep though.

[tom66]

Re: Samsung PS42B450 Y Main

But you see nothing the other way? The buffer is most likely OK then.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

Could the X Main be popping the Y main?

[tom66]

Re: Samsung PS42B450 Y Main

That is not only possible, it is quite likely.
A bad X-main on these sets risks damage to the Y-main, and vice versa, due to how the energy recovery circuit is chained.

[thestigp11gt]

Re: Samsung PS42B450 Y Main

So it is best just replacing them both. How can one test these boards?