LG OK75 - Troubleshooting: No MD Operation (Tray Motor)

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Only for training and service purposes.
< MAIN board bottom view >
IC400
IC400
IC401
IC401
< Waveform
for driving tray open/ close motor >
MOT_ CL OS E
MOT_ OP EN
LO+(RED)
LO-
ONE POINT REPAIR GUIDE
NO OPERATION OF MD
When no sound output in the CD function, you can not listen to music reading data from a CD
disc if the servo motors in MD don’t work. This step is for checking the TRAY OPEN / CLOSE
MOTOR among them.
5-3. TRAY OPEN/ CLOSE MOTOR
5-3-1. Solution
Replace IC400 on MAIN board.
5-3-2. How to troubleshoot (Countermeasure)
1) Check MOT_OPEN & MOT_CLOSE signals from pin P5, L4 of IC501 to IC400.
 If no signal, check M_5V to IC400.
2) Check LOAD± from IC400 to CN401 for driving the tray open / close motor. It is about 3.85 Vp-p.
 If no signal, check M_5V to IC400. If it has any trouble, replace it with a new one.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the tray motor is sort-circuit or has any trouble, it can not open or close the tray.
Please check the function after changing another MD.
5-3-3. Service hint (Any picture/ Remark)
M_CL: pin6
M_CL: pin6
M_OP: pin7
M_OP: pin7
LO+: pin9
LO+: pin9
LO-: pin10
LO-: pin10