Samsung PN51D550C1F Clicking and flashing power led

[pr0cess0r]

Hello, i just got this tv and i found out it has alredy been repair. They repaired the x-main but the last owner told me that the repair lasted 15 minutes then 4 hours in a secound repair.

is it possible that a bad y-main will kill the x-main?? What i want to do is to buy a new x-main and test it but dont want to toast it.

If i disconnect the main-x the tv will turn on (no red light) but im not able to turn it off.

If i disconnect the fcc cable from the main-y boad now im able to turn it on and off normal.

here are some pictures.

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

I will test VS and VA with x mainboard disconnected to see if y is ok. I will also test y buffer for short. Id everything is ok i think i will buy a new x main and hope it fix it!

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

i tryed to test VA and VS and i dont know what i did... but now the tv is not clicking anymore and the led is not flashing on the control board

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

Ok i burned the fuse on the control board now i can do some more test...

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

ok VS and VA are ok and dropping with the y main connected. If i completly disconnect y main then they dont drop.

Is it normal that vs and va drop like this when x main is disconnected ?

[RCA2000]

Re: Samsung PN51D550C1F Clicking and flashing power led

How far do they drop...and how fast?

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

VA drop to 2 Volt in about 30 sec
VS drop to 12 Volt in about 15 sec

[ljintexas]

Re: Samsung PN51D550C1F Clicking and flashing power led

Y buffers and possibly a few transistors on Y main. check y buffers.. MOSFETs for short..in circuit they are all three common..if one is shorted all 3 will show short.

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

i was under the impression that the power go down since the control board detect that the main X is not there and cut power?

When you talk about mosfet is it on the buffer or y main??

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

Can you help me ifdentify those mosfet and transistor you talk about?? here are some hi res picture of all chip i think you talk about. I dont know how to test.

Thank you.

[ljintexas]

Re: Samsung PN51D550C1F Clicking and flashing power led

Each buffer board should have three mosfets on it..if any of them are shorted all of them will be..most likely took out a few components on Ysus. Good clear pictures of the boards in your set will help.

[ReeceyBurger123]

Re: Samsung PN51D550C1F Clicking and flashing power led

That's weird, I would say something is intermittent. If there was a shorted fet on Ybuffer or Ymain it would have blown up instantly not 15mins or 4 hours later. Have you checked for cold solder joints on the Ymain ?

[tom66]

Re: Samsung PN51D550C1F Clicking and flashing power led

Each buffer board should have three mosfets on it..if any of them are shorted all of them will be..most likely took out a few components on Ysus. Good clear pictures of the boards in your set will help.

Does not apply to this model, only to older LGs. Samsung do not use FETs on their buffers, they are on the Y-main instead.

[pr0cess0r]

Re: Samsung PN51D550C1F Clicking and flashing power led

That's weird, I would say something is intermittent. If there was a shorted fet on Ybuffer or Ymain it would have blown up instantly not 15mins or 4 hours later. Have you checked for cold solder joints on the Ymain ?

I tested the buffer i found no short on it. What i need to know for sure is if a slowly dropping VS and VA can be because the xmain is disconnected from the y main and the controller turn it off?

[ljintexas]

Re: Samsung PN51D550C1F Clicking and flashing power led

Thanks for correcting me Tom..I had my sets mixed up there!