LG OM7550 Service Manual

3-9
ONE POINT REPAIR GUIDE
8. NO BOOTING IN CD/USB FUNCTION
After you turn on power key and displayed message in the following order (HELLO  VOL XX 
CD or USB) on VFD, it will not display other message on VFD, and it will not boot-up normally.
8-1. NO VCC33, VCC12
8-1-1. Solution
Please check and replace IC505, IC500 on MAIN board.
8-1-2. How to troubleshoot (Countermeasure)
1) Check Voltage of IC505 pin3 on MAIN board.
 If IC505 pin3(about 4.9 V) & D500 Input 5.6 VA doesn’t come out, check 5.6 VA from SMPS board.
2) If IC505 pin3(about 4.9 V) is normal, check the PWR_CTRL(IC505 pin2) is high (about 3.3 V).
 If PWR_CTRL isn’t high, check pin B2 of IC501 & R524, R522.
3) If PWR_CTRL is high, check R524 and if there’s no defective component then replace IC505.
4) If 3.3 V(VCC33) is normal, check 1.2 V output(pin2) voltage of IC500.
 If 1.2 V of IC500 pin2 doesn’t come out, then replace IC500.
8-1-3. Service hint (Any picture / Remark)
< MAIN board top view >
< MAIN board bottom view >
IC505
IC505
D500
D500
IC500
IC500

LG OM7550 Specifications

General

Brand	LG
Model	OM7550
Category	Stereo System
Language	English