LG MCV-903 Schematic

SECTION 3. AUDIO

jomi

ELECTRICAL PART

AUDIO ELECTRICAL TROUBLESHOOTING GUIDE

1. MICOM PART CHECK I

MICOM PART

HECK I

YES

Check

CN710 7PIN

P- SENS

YES

Is IC101

KIA7042

5V?

YES

Check the IC100

87F5NC8A 4

PIN power

YES YES

OK OK

NO

Refer to SMPS

Troubleshooting.

Is IC101

KIA7042

input 5V?

YES YES

Is IC101 KIA7042

output 4.3V?

NO NO

Check the

related part of IC101

KIA7042

Replace the related

part

3-1

LGE Internal Use Only

2. MICOM PART CHECK II

jomi

MICOM PART CHECK II

YES

Check CN710

6PIN 5.6V

YES

Check the

power of both

D102 and D101 1SR35

(Is the power of

IC 100,14.40.55

89 4.8V?

YES

Check IC102

KIA7031 input power.

NO

Refer to SMPS

Troubleshooting.

Check the D101,102

1SR35 output 5V

YES

Check the

related part.

YES

OK

Check the D101

1SR35 output 5V

NO

Replace the related parts.

Check & replace the related

part.

Check IC102 KIA7031

output power

Check IC100 87F5NC8A

8 PIN power.

OK OK

LGE Internal Use Only

YES

Check

IC 102 KIA7031

input power (4.8V or input power

(4.8V or higher)

YES

Check IC 102

KIA7031 output

power

YES

3-2

NO

Check R1A9 680 Ω

YES

OK

Check the operation status of

R191 10K and R110 4.7K

YES

Replace the related parts.

Only for training and service purposes

NO

3. MICOM PART CHECK III

jomi

MICOM PART CHECK III

YES

Check the IC100 14.40.56.89

input power (4.8V or higher)

YES

Check the operation

status of

X101:32.768KHz and

X100:9.8304MHz

YES

OK

NO

Refer to MICOM Par I,II Troubleshooting

3-3

LGE Internal Use Only

4. FLD DISPLAY PART CHECK

jomi

FLD DISPLAY CHECK

YES

Check the power of CN710

10 11 12 PIN

YES

Check

10 PIN → - 27V

11 PIN→ 20V 12 PIN→ 25V

YES

Check the

connecting condition

and the power of P3702

40PIN: FL- 20

39PIN: FL+ 25

38PIN: VKK-28vor higher

39PIN: 5.6V

YES

Check

IC304 PT6324

power 50 PIN VKK:-28V

9.52 PIN +5V

NO

Refer to SMPS

Troubleshooting

Check CN710

assembly

YES

Check each pin

YES

OK

If 5V is failed, check the input and

output power of D319 1SR35

YES

Check the related part

NO

Replace the related part

Replace the related part.

Check IC100 →

IC301 DATA communication

PIN PIN

27 PIN → 3PIN STB

26 PIN → 2PIN D

28 PIN → PIN CLK

FLT turned on

OK

LGE Internal Use Only

YES

NO

YES

OK

IC100 IC303 27 PIN → 3PIN STB 28 PIN → 1PIN CLK

Check Data output

YES

Check the data at both terminals

of LINE R330,331,332

YES

Check the related part

YES

OK

3-4

NO

Replace the related part.

Only for training and service purposes

5. IC103 S-24CS16A01-J8T1GE CHECK

A

jomi

CHECK IC100

LC87F5NC8A 81,82

YES

81 PIN DATA 82 PIN CLK

YES

NO

Check the communication between

both terminals of R189,190 100Ω

CLK

DAT

Check MICOM power 5V

YES

NO

Refer to micom

troubleshooting.

OK

Check the related part.

YES

OK

NO

Replace the related parts.

3-5

LGE Internal Use Only

6. AUX FUNCTION PART CHECK

jomi

AUX FUNCTION PART

YES

Make sure that

JK800 is

YES

Check the input

waveform of IC200 (BU4052)

4,11PIN

YES

Check the output waveform of

IC200 (BU4052) 3,13PIN

YES

Check the input

waveform of IC801

(MC4580) 2,6PIN

YES

Check the output

waveform of the PN709

6 PIN L_ CH

8 PIN R_ CH

NO NO

NO

Check IC200 (BU4052)

16PINVDD, 8PIN VSS power

YES

Replace the related part

Check the IC801

(MC4580) 4PIN VSS, 8PIN

VDD power

YES

Replace the related part

NO

Check the M-COM (IC301)

83PIN, 84PIN communication

Refer to SMPS

Troubleshooting.

OK

LGE Internal Use Only

YES

3-6

Only for training and service purposes

8. TUNER FUNCTION PART CHECK

jomi

TUNER FUNCTION PART CHECK

YES

Check the TUNER module

(TU601) operation

YES

Check the input

waveform of IC200( BU4052) 1,12PIN

YES

Check the output

waveform of IC200 (BU4052)3, 13PIN

Check the input waveform of IC601

(BU4052)2, 15PIN

YES

Check the input waveform of IC801.

NO

Check the TUNER MODULE power

(check the 2PIN 9V)

Check the IC200 (BU4052)

16PINVDD, 8PIN VSS power

YES

Replace the related part

Check the IC801( MC4580)

4PIN VSS, 8PIN VDD power

OK

3-7

YESYES

Replace the related part

LGE Internal Use Only

9. TAPE FUNCTION PART CHECK

jomi

TAPE PCB ASS`Y

YES

Check the input waveform of

IC200(BU4052) 2, 15PIN

YES

Check the output waveform of IC200 (BU4052)3, 13PIN

Check the input waveform of IC601 (BU4052)2, 15PIN

YES

Check the input

waveform of IC801(MIC4580)2 ,6PIN

YES

Check the output waveform of the PN709

6 PIN L_ CH

8 PIN R_ CH

YES

NO

Check the IC200 (BU4052)

16PINVDD, 8PIN VSS power

YES

Replace the related part

Check the IC200 (BU4052)

16PINVDD, 8PIN VSS power

YES

Replace the related part

LGE Internal Use Only

OK

3-8

Only for training and service purposes

10. TAPE PLAY PART CHECK

jomi

TAPE PLAY PART

YES

Check the

IC201 (HA12237) 16

PIN 12V input

YES

Check the IC201: 5.26

PIN Signal Output

YES

NO

NO NO

Refer to SMPS

Troubleshooting.

Check the

A/ B DECK HEAD

YES

Check A DECK HEAD input

IC201 32, 39PIN

YES

NO

Check the related part

Replace HEAD WIRE and

Mecha

Replace the related part

Check the IC201

14 PIN MUTE

operation

YES

OK

NO

YES

OK

Check the IC202 10 PIN

HIGH operation

YES

Check the related part

YES

OK

3-9

NO

Replace the related part

LGE Internal Use Only

11. TAPE REC PART CHECK

jomi

TAPE REC PART

YES

Check the

IC604 PS9829

#49, #52 PWM

output

YES

Check the IC201 7.24 PIN

REC input

YES

Check the IC201 10.21

PIN output

YES

NO

NO NO

Refer to SMPS

Troubleshooting.

Check IC100 23PIN HIGH

YES

OK

Replace the related part

Check the L203 2.3 PIN

oscillation

YES

. Check P2203 5.3 PIN input

. Check 8 PIN ERASE input

YES

OK

LGE Internal Use Only

NO NO

Check Q205(D1304)

BASE HIGH

YES

OK

3-10

Check the IC202 4 PIN

HIGH operation

YES

Replace the related part

Only for training and service purposes

12. MIC PART CHECK

jomi

MIC PART

YES

Apply JK302, JK303

and check. CN301

2PIN, 4PIN output

YES

Check the P312

2PIN. 4PIN input

YES

Check the IC304

(BA3308) 8 PIN input

YES

Check the

IC304 (BA3308) 3PIN

output

YES

Check the P306 15PIN output

(FRONT PCB Ass`y)

YES

Check the P7302 15PIN input (MAIN PCB Ass`y)

YES

Check the input at both

terminals of R804,812

YES

Check the IC603

1, 2PIN input

NO

Check

IC304 6PIN 12V

YES

OK

NO

Check the power at

both terminals ofFB301

YES

3-11

LGE Internal Use Only

YES

jomi

IC603 → PS9830

communication check

9 PIN SOTO → 33PIN SDIN

10PIN LRCK → 32LRCK 11PIN MCLK → 30MCLK

13PIN BCK → 31BCK

YES

NO

IC100 38PIN →

IC603 Check the REST

operation

YES

Check each communication

line resistance

YES

NO

Check the IC603

input power.

YES

Check the

power at both terminals

of FB803

YES

NO

Replace the related

part

OK

Check the

PS9830 input

YES

OK

13. PWM MODULATION PART CHECK I

PWM MODULATION

PART CHECK I

YES

Check CN701

9PIN 5V

NO

Troubleshooting.

Refer to PS9830

Troubleshooting

Refer to SMPS

OK

YES

Check IC505

input 5V and

output 3.3V

YES YES

LGE Internal Use Only

NO

IC505 input power

Check

5V

NO

Check CN701

9PIN 5V

3-12

Only for training and service purposes