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< MAIN board top view >

ONE POINT REPAIR GUIDE

3. VFD IS NOT DISPLAYED WHEN POWER ON THE SET

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

3-1. VFD (DIG300)

3-1-1. Solution

Please check and replace DIG300 on FRONT board.

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

1) Check if 39V, FL+ and FL-are output from SMPS to VFD via the main board.

2) Check if the IC101 outputs VFD_RST, VFD_CLK, VFD_STB, and VFD_STB to the front board.

3) Check if the VFD grid current amplifier circuit (Q301, Q303) on the front board.

Check the drive signal to the transistor’s base.

 If the control signals from VFD (DGND_2, VH, VDD) isn’t output, replace VFD with a new one.

 If the transistor doesn’t work, replace it.

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

LG CMS9540F Service Manual

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