Samsung PN51E450A Tv turn on but no picture

[Louis82]

Hello guys,

I have a Samsung plasma tv PN51E450A that is giving me a headache. It responds to power button, i can hear chime going on and goes off when i push the button for second time. Remove the back cover, using my multimeter, I can see that VS voltage goes up to 206V for a second and immediately drops to 10V. If i'm not mistaking this tv has the Y/X main board built in one. I checked transistors on this board and it doesn't seem to have anything wrong. I also checked for burned IC's on buffers, but nothing. Power supply has all voltages except VS and VA. I tried to do the jump of PS-ON with a 5V line but didn't work. Power supply didn't kick on.(any help here)
By disconnecting Y/X main board from power supply, voltage doesn't even try to go up for a second.

By checking shopjimmy's website i found that they sell the EEPROM as a possible fix for Tv turning on with no backlights. (LED indicator shows tv is on but no picture).
Any suggestions? Have you guys had a successful repaired of this symptom by replacing EEPROM?

Thank you in advance.

Note: I'm posting a few pic of boards. They don't belong to tv i'm working but they are the correct ones.

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Picture of the inside. Thank you.

[Alastair E]

Re: Samsung PN51E450A Tv turn on but no picture

How does it react if you pull the LVDS and jumper the test-sig points on the control-board?

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Alastair, thank you for replying. I did remove the LVDS from main board and tv turn on but can't do anything else. Meaning that if i try to push power button to turn it off it will not do it. Still no VS voltage.

I did not see the 4 pins where i could try jump to test pattern.

[drussell]

Re: Samsung PN51E450A Tv turn on but no picture

Have you checked all the transistor-looking devices on the Y-Main (mostly IGBTs and diodes) for shorts?

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Hi drussell. Yes i did checked transistors on Y main board. Couldn't find any problem there.

[drussell]

Re: Samsung PN51E450A Tv turn on but no picture

Do your Ve and -Vscan come up to full voltage briefly on power up also?

The 60E530 and E550 have flakiness in the -Vscan supply that will cause the set to go into protection but your TV uses a different PWM controller chip so it's less likely that but worth a quick check anyway.

You should figure out that logic board test also, would be good to try that. If you post a close-up pic of the logic board we can probably point you to the jumper, assuming there is one. (There should be...)

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Here is a picture of logic board. I just noticed that square with 4 holes. is that the new pattern test point? I was looking for pins. If that's the test point, what point should I shorted out? 3 and 4?

[drussell]

Re: Samsung PN51E450A Tv turn on but no picture

I just noticed that square with 4 holes. is that the new pattern test point? I was looking for pins. If that's the test point, what point should I shorted out? 3 and 4?

Yes, that's the one, and yes, holes 3-4.... I use a spade connector with the spade bent just right to stick in there but any little piece of wire or an aligator clip or whatever will work just fine if it connects those two together, just don't go through to the chassis on the other side.

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

I got my answer after reading another thread. Will try jumping 3 and 4 and will check Ve and -Vscan voltage tomorrow when i get to my work bench. Will keep you updated druseell. Thank you

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Great! Thanks drussell.

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Well before you go, if after doing this I get pattern on screen i should assume everything is fine except main board. correct?

[drussell]

Re: Samsung PN51E450A Tv turn on but no picture

Well before you go, if after doing this I get pattern on screen i should assume everything is fine except main board. correct?

Yup. If it works, double check the main board to be sure it's getting power, no blown fuses or obvious missing voltages on the various regulators.

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

Great. Will do that. Last question, by any chance do you know how i can activate the power supply without having it connected to main board? I know there is a jump on PS-ON but I'm not sure.

[drussell]

Re: Samsung PN51E450A Tv turn on but no picture

Last question, by any chance do you know how i can activate the power supply without having it connected to main board? I know there is a jump on PS-ON but I'm not sure.

Jump between PS-ON and ground.

It's easiest to do this by disconnecting the power to the main board at the main board end and sticking a wire in it between the PS-ON and GND sockets in the connector on the end of the cable. You could also do it with a wire stuck in the back of the connector at the power supply or whatever turns your crank.

[Louis82]

Re: Samsung PN51E450A Tv turn on but no picture

UPDATE: Tried the jump on power supply and the short on logic board (pin3 to4) and not changed.
Found the Y-Buffer was the problem, even though the chips did not look physically burned.
I carefully disconnected the Y buffer from Y-Main and tv stayed on. All voltages present.
Ordered new Y-Buffer and tv worked. Over 30 days, tv still paying fine.
Thank you for the help Drussell.