Samsung PN51D440A5 No Picture But Has Sound

[sluhbmet]

I have a Samsung PN51D440A5 plasma tv with no picture but still has sound. Initial troubleshooting found Vs on the power supply is getting dragged down to around 19 volts when it is connected to the y-sus, but raises to 208 volts when the y-sus connector is removed. This made me think the y-sus or x-sus is at fault. Also the light on the logic board is blinking slower than what I remember in the past from these units. With all other cables re-connected I found that the light on the logic board blinks faster if I disconnect the ribbon cable going from the logic board to the y-sus. My gut is telling me that I've got a bad y-sustain and/or y-driver. I do worry about a bad panel but I can say that it does not have any cracks or any visible defective areas. It was working fine one second and then no video the next. Anyone agree or disagree with my thought process? Thanks for the help.

[tom66]

Re: Samsung PN51D440A5 No Picture But Has Sound

On this set, does the X-main power connect to the Y-main board? If so, try unplugging the link between them and leave in the Y-main to power board connection.
A bad panel wouldn't cause a fault like this.

[sluhbmet]

Re: Samsung PN51D440A5 No Picture But Has Sound

tom66,

Yes this model has the x-main power coming from the y-main board. I unplugged the x-main power connector and found no change. Vs is still dropping low (16-19 volts) when tv is powered up. Any other thoughts?

[tom66]

Re: Samsung PN51D440A5 No Picture But Has Sound

I suspect you have shorted transistors on the Y-main. Remove the board and check all devices mounted on the heatsink.