LG 42LH20 Service Manual page 37

Power Supply Backlight Drive Signal Effects
Power Supply Backlight Drive Signal Effects
Waveform taken using loose coupling. Clip the
probe to one of the Backlight wires. Use
caution, there is 1.2Kv in the wire.
Slow scope setting to 2.4mSec to see the effects
of PWM on the waveform.
The PWM amount can cause the frequency to be
measured differently.
VBR-B
PWM-DIM manipulates
the ballast drive IC.
VBR-A
BR1 (A-DIM) is not used.
LCD or PLASMA 2009 Model
37