Slide 49
Voltage Distribution (Panel Drive Voltages Vda)
Analysis of a shorted Vda condition
Vda is generated by the Power supply and is used by the panel.
Vda is routed through the C boards before it is connected to the panel.
On the C boards, several 1 ohm fusible resistors (matching the number of connectors
between the C boards and the panel) are used on the Vda line.
A shorted Vda is usually caused by the panel and very rarely by the power supply. Any of the
C boards, even though is not likely, can also cause a shorted Vda.
To check if Vda is shorted, unplug the TV and discharge any possible residual charge from
the Vda and Vsus lines. (Use a 500 ohms resistor at least 5W).
Then measure resistance or continuity on pin 1 of connector P35. (A resistance reading lower
than 1K (1000 ohms) is considered to be abnormal.)
If a short circuit is found on connector P35, check the P board and the C boards. It’s not likely
for the 1 ohm resistors on the C boards not to open when the panel is shorted.
Depending on the model, a short circuit of the Vsus can cause a 3 fast blinks or a normal 8 blinks
shutdown condition.
A shorted Vda caused by the panel will not trigger a 3 nor an 8 blinks shutdown condition because of
the 1 ohm fusible resistors used on the C boards. The resistor in line with the defective IC on the panel
causing the short circuit opens allowing the TV to stay on.
The symptom expected is a 3” black bar from top to bottom on the area of the screen controlled by the
panel drive IC on the panel causing the short circuit.
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