Samsung PN51D450A2D, no picture, sound works

[expertpc]

This plasma tv is not showing a picture, the sound works when powering on and off.

Vs, Va, Vscan, and Ve all show the correct voltages immediately after the system is powered up, then the logic board flashes the on 5 second off 2 second pattern indicating panel or y-main/x-main failure and the voltages drop off.

Upon forcing the tv to power on via jumper for PS_ON and GND on pulled CN101 from the main board, disconnecting LVDS, and shorting pins 3&4 on the logic board to initiate the test sequence there is still no picture.

There are no visible cracks in the screen or around the edges, there are small horizontal lines through the entire display leading me to believe the panel is bad but it could just be the way the screen is made. Is there any way to verify the y-main and y-buffer boards are functioning short of replacing them? The fast track guide only states suspect logic buffers or panel.

Thanks for any insight.

[Hamie]

Re: Samsung PN51D450A2D, no picture, sound works

You see the 2 copper test points on the buffers near the top. Labelled svt_out (or similar)

Measure across the 2 points. Low ohms = shorted buffer.

[Sevenqi]

Re: Samsung PN51D450A2D, no picture, sound works

First check if the buffer board shorted any ICs (There is many threads to tell you how to with multimeter).
If buffer ICs not shorted, then check the big black color resistors, burnt or shorted ? If screen issues, those resistors may be burnt especially your screen looks interlace.
If buffer has no shorts, then check the x-main and y-main boards. x-main failure is common for this model.

[expertpc]

Re: Samsung PN51D450A2D, no picture, sound works

So I put it on a workbench with better lighting this morning and laughed, somebody has been in this before.

Thank you both for the buffer test info. It has normal ohm reading and the IC's don't appear to be shorted.

Here was why I laughed, its amazing what you miss when you're tired.

Missing tape on the Y buffer and missing MOSFETs.