LG OK75 User Manual

3-5
Copyright © 2018 LG Electronics Inc. All rights reserved.
Only for training and service purposes.
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 (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)
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R810(TP 841)
Q801 Emitter
about
30 Vp-p
< TOP FRONT circuit >
< Waveform of the grid current driver>

LG OK75 Specifications

General

Output Power	1000W
Bluetooth	Yes
Karaoke Creator	Yes
DJ Effects	Yes
USB Playback	Yes
Multi Jukebox	Yes
Party Accelerator	Yes
Type	Mini Hi-Fi System
Audio Playback	MP3, WMA
FM Radio	Yes
CD Player	Yes
Brand	LG
Model	OK75
Category	Stereo System
Disc Formats	CD, CD-R, CD-RW
Radio	FM
Audio Inputs	USB
Speaker Configuration	2.0 Channel