LG OM7550 - Operation of MD

3-15
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 sled motor among them.
9-2. SLED MOTOR
9-2-1. Solution
Replace IC401 or IC400 on MAIN board.
9-2-2. How to troubleshoot (Countermeasure)
1) Check the SLDO signal from pin23 of IC401.
 If no signal, check 3.3 V (RF) and X400.
2) Check the SLED+ & SLED- from IC400 to CN401 for driving SPINDLE motor. It is about 2.9 Vp-p.
 If no signal, check +1.8 V and +5 V for IC401.
3) Check if the FFC cable is solidly connected between CN401 and MD.
4) Check the MD.
 If the sled motor is sort-circuit or has any trouble, it can not move the pickup module.
Please check the function after changing another MD.
9-2-3. Service hint (Any picture / Remark)
< Waveform of SLED- & SLED+
for driving SLED motor >
zsR
zs
T
< MAIN board top view >
SL-
SL-
pin9 of CN401
pin9 of CN401
SL+
SL+
pin7 of CN401
pin7 of CN401
IC400
IC400