Vfd Is Not Displayed When Power On The Set - LG CM4330 Service Manual

When power on the set, any icons or characters on VFD are not displayed.

3-1. VFD

3-1-1. Solution

Please check and replace DIG502 on FRONT board.

3-1-2. How to troubleshoot (Countermeasure)

1) Check if VKK, FL+ and FL- are output from SMPS to VFD via the MAIN board.

2) Check if IC102 outputs VFD_D0, VFD_CLK and VFD_STB to the FRONT board.

3) Check the GR signal(pulse signal) of IC501 on the FRONT board.

Check the SG signal(pulse signal) of IC501 on the FRONT board.

If the GR and SG signal isn't output, replace IC501 with a new one.

If the GR and SG signal is output, replace DIG502 with a new one.

3-1-3. Service hint (Any picture / Remark)

ONE POINT REPAIR GUIDE

GR SIGNAL

ABOUT 30V

< Waveform of GR and SG signal >

3-5

SG SIGNAL

ABOUT 30V