Vfd Is Not Displayed When Power On The Set - LG OK75 Service Manual

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 (VFD801)
3-1-1. Solution
Please check and replace VFD301 on TOP FRONT board.
3-1-2. How to troubleshoot (Countermeasure)
1) Check if VFD_12V, DVCC_3.3V and VCC_5V are output from SMPS to VFD via the main board.
2) Check if the IC501 outputs VFD_CLK, VFD_STB, and VFD_DAT to the top board.
3) Check if the VFD grid current amplifier circuit on the top board.
Check the drive signal to the transistor's(Q801,2) base.
  If the control signals from VFD (DGND, VDD) isn't output, replace VFD with a new one.
3-1-3. Service hint (Any picture/ Remark)
< TOP FRONT circuit >
ONE POINT REPAIR GUIDE
R810(TP841)
Q801 Emitter
< Waveform of the grid current driver>
3-5
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