Samsung PN42A450P1D - No Picture

[kmoonen]

Hi All

I have a Samsung PN42A450P1D with no display, the TV powers on, blue light is on in the middle, the buttons on the side make noise when you hit them, power button works, but there is no display

VA, and VS voltages are right on target no bulging caps

any ideas?.

[Pentium4]

Re: Samsung PN42A450P1D - No Picture

When you shine a flashlight on the screen, can you faintly see an image? Try it with the lights off. When you first power it on does the backlight go on and then off after a few seconds? Maybe the inverter transformers are bad.

[Glitcher]

Re: Samsung PN42A450P1D - No Picture

Probably bad buffer boards and or y-main. check buffers for any shorted ICs and the Y-main for bad mosfets.

[dcapper]

Re: Samsung PN42A450P1D - No Picture

I'm debating if I should fix almost the identical one. I might have some boards for you if I don't get a logic board for mine.

[Fwrothy]

Re: Samsung PN42A450P1D - No Picture

I'm debating if I should fix almost the identical one. I might have some boards for you if I don't get a logic board for mine.

Hey dcapper what did you end up doing with the set?

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

Hello, This is my first try to enter. I have the same model. It was my daughters and it was working then she moved. When she tried to turn on, no picture but sound ok. sometimes if off for a while then start up picture comes on for 15 sec and goes off, sound still good. checked fuses and visual check ok. thinking Y sus board.

[Pentium4]

Re: Samsung PN42A450P1D - No Picture

Can you post some pictures of the boards?

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

here are pic's. hope you can see all right.

[Pentium4]

Re: Samsung PN42A450P1D - No Picture

Looking at the 3rd picture, check that gold cap next to the two fuses. The way the top looks, it may have bulged from the bottom because it looks like the sleeve has been pulled down a little bit. Next, I would check the voltages on the cable going from the PSU to the mainboard.

[Hamie]

Re: Samsung PN42A450P1D - No Picture

Check vsc voltage when the picture disappears.

Test point located here:

[Hamie]

Re: Samsung PN42A450P1D - No Picture

Can you also remove the stand guide that's covering some of the control board and take another picture of the full board.

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

here is pic of full board. haven't taken cap off yet to check bottom. Thanks for all info

[Hamie]

Re: Samsung PN42A450P1D - No Picture

Vscan voltage?

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

Thanks for reply. If I did it right there was no voltage there. It was from VSCN spot and grd correct? and AC also?

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

Sorry about that. I did it again. picture came on and vscan volts 190 dc. picture went off after about 40 sec. and volts jumping from 185 to 192 back and forth.

[Hamie]

Re: Samsung PN42A450P1D - No Picture

Ok just to be sure can you run test patterns on the TV.

To do this:
On this litter black square with 4 pins, short out pins 3 and 4 with a croc clip or piece of wire.



And remove the lvds cable that connects this board to the main av board.

This one here:



Let me know who long the test patterns last.

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

made it to test screen. lasted 60 sec.

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

follow on to last entry. the test patterns were working fine and changing colors. then after 60 seconds the picture stopped. haven't heard any popping or cracking. I have turned off and sometimes unplug and then restarted after hours passed. the picture and sound comes on and then after 30 to 60 seconds the picture stops but the sound continues. hope this info helps

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

I have found a used Y sus board and Y buffer for about $ 50. on Ebay. Anybody think it might be worth a shot to try it?

[nelsonba44]

Re: Samsung PN42A450P1D - No Picture

Update. I purchased a Y sus board and Y buffer from Tri-State Module for $52. Installed and still no picture but sound. So much for that guess. Maybe in power board, will check some more before trashing.