Repair Journal | Samsung PN43D450A2FXZA (N102)

Samsung PN43D450A2FXZA (N102) | 43" PDP

Symptoms:
TV will not turn on. Relay clicks repeatedly on power-up attempts.

Diagnostics:
Test critical voltages.

Panel sticker rated voltages:
VS: 205V
VA: 58V
Vsc: -180V

With everything hooked up:
VS: 0.3V-0.5V
VA: 0V
Vsc: -- (not measured)

Remove power connector (X and Y-MAIN):
VS: 205V (spike and shutdown)
VA: 55V (spike and shutdown)
Vsc: -- (not measured)

-NOTE- 
The reason the voltage spikes and disappears quickly is because the circuit is not complete (i.e. the boards needed for operation are disconnected from the power circuit) and the TV goes into shutdown immediately. When you plug in the power cord with these boards disconnected, you can have your DMM probes on the VS and VA test points beforehand. This allows you to see if the PSU is operating correctly. Seeing the correct voltages at startup confirms that the short is elsewhere.

Continuity tests (power off, X and Y-MAIN disconnected)
Set your DMM to continuity mode and place one probe on the chassis and another at each of the following test points. If there is continuity (i.e. there is a tone that sounds when my DMM detects a complete circuit), you have a short at the tested point.

VS: OK
VA: OK
Vsc: OK
XS_E: SHORT
XS_C: SHORT
XG_E: SHORT
XG_C: SHORT

The short on the X-MAIN board indicates that this is the problem board.

Solution:
Replace the X-MAIN board. It is most certainly bad. While you're at it, get a hold of a LOGIC BOARD (the green one just south of the PSU) and replace it as well. Don't ask me why, but this vintage of 43" Samsung Plasma (the "D" in the model number "PNxxDxxx" indicates it was manufactured in 2011) seems to be a victim of this failure often. If you have a shorted X-MAIN, there is a 70-80% chance that the LOGIC is also shot.

Be sure that you immediately upgrade the firmware on this television after installing the new LOGIC and X-MAIN boards.

-PROTIP- Now, if you were working with a "PN51Dxxx" (the 51" plasma model from this year), it is more often the Y-MAIN and X-MAIN. You would get a short on the Vsc point during continuity testing if the Y-MAIN was bad. 

Pictures will be available soon!