LG Multiplex 72, Service Manual

3-3

3.2.3 AUDIO LEVEL  Checking and adjustment

1) Connect “+” terminal of RMS meter(Auto level meter) to

C392 on the main PCB Audio out and “-” terminal to
GND.

2) Check that if audio level of RMS meter satisfies with the

spec, If audio sound is weak, adjust the A/C head
azimuth screw.

3) Audio level spec

1K :0.5  

!

0.1Vrms

6K :1KHz 

!

1.5dB

3.3. X-DISTANT/P2,P3 ADJUSTMENT

3.3.1. NECESSARY INSTRUMENT

1) SP PAL TAPE
2) OSCILLOSCOPE
3) 10:1 PROBE : 2 PIECES
4).SPECIAL DRIVER FOR ADJUSTMENT(P2,P3,X-

DISTANT(NUT),AUDIO(NUT))

5) RMS METER(AUDIO LEVEL METER)

3.3.2. ADJUSTMENT PREPARATION

1).Connect oscilloscope(CH-1) to J261(H/SW) on main PCB.

(Use for trigger of CH-2 )

2) Connect oscilloscope(CH-2) to J261(RF) on main PCB.

(Use waveform of CH-2)

3) Play by inserting SP PAL TAPE. (2HD:normal tape)
4) After the picture is appeared, make initial condition by

pressing the tracking adjustment up(+) button of the
remote controller.

3.3.3. X-DISTANCE ADJUSTMENT

1) Turn the X-distant adjust groove of the deck right and left

to maximize the scope waveform.

2) Check that if waveform satisfies with the linearity by

pressing TRK Up(+) and  Down(-) button.

3) Tighten the X-distant adjust screw.

3.3.4. P2/P3(RF LINEARITY) CHECK & ADJUSTMENT

1) Adjust p2 & p3 so that the the RF envelope waveform of

the oscilloscope becomes C in figure 2.

2) Check if the envelope waveform becomes maximum by

pressing TRK Up(+),Down(-) button one step.

3.4. PG ADJUSTMENT

Adjust it after finishing controlling the Deck.

3.4.1.NECESSARY INSTRUMENT

1) SP PAL TAPE
2) OSCILLOSCOPE
3) 10 : 1 PROBE : 2 PIECES

3.4.2. ADJUSTMENT

1) Insert and play the SP PAL TAPE.
2) Connect the oscilloscope(CH-1) to H/SW(J261) on the

main PCB and trigger in setting the VOL/DIV to 1V range. 

3) Connect the oscilloscope(CH-2) to video out(C571) on the

main PCB and set the VOL/DIV to 500mV range. 

4) Set the TIME/DIV of oscilloscope to 50us range.
5) If press P-CHECK of SVC Remote control “A-PG>>>” is

appeared in the display, and PG adjustment signal
become 412uS 

! 

100uSec.

4. ASSEMBLY LINE ADJUSTMENT

4.1. DVCO adjustment

1) This is for adjustment of VCT3834, crystal oscillator

frequency after receiving a company Digital pattern.
(PAL : EU05CH, NTSC : 13CH)

2) When entering adjustment mode by pressing IN-START

button, DVCO adjustment is operating automatically. (T/X
doesn’t operating occasionally during DVCO adjustment,)

4.2. FOCUS ADJUSTMENT

1). Receive the LG standard pattern(digital pattern, Fig5).

2). Set the picture condition on ‘STANDARD’ mode.
3)Adjust the focus volume of FBT for the best focus of

horizontal line A, vertical line B.

4.3. Purity & Convergence 

adjustment

4.3.1. PURITY adjustment

1) Preparation

¤

Receive the RED Raster Pattern for purity adjustment.

(P-50CH or N-11CH)

¤Ł

Demagnetize the CPT and Cabinet with a degaussing
coil.

2) Adjustment

¤

Pre-adjust the static convergence(STC) with 4 and 6-
pole magnet.

¤Ł

Push the DY(deflection Yoke)all the way to the CPT

panel.

¤Ø

Turn the purity magnet(2-pole magnet) so that the

‘green’ portion of left side and the ‘blue’ portion of right
side have same portion.

¤Œ

Pull the DY slowly and fix it when the whole screen

become red.

4.3.2. Convergence adjustment

1) Preparation

¤

Receive the cross Hatch pattern for convergence

adjustment.(P-07CH or N-09CH)

¤Ł

Let the contrast at the adequate luminance level.

ADJUST PERIOD (6.5H = 412us)

PG ADJUST WAVEFORM

* CAUTION: SET THE TRIGGER MODE OF OSCILLOSCOPE TO DC

ADJUST PERIOD (6.5H = 412us)

PG ADJUST WAVEFORM

* CAUTION: SET THE TRIGGER MODE OF OSCILLOSCOPE TO DC

<Fig4>

<Fig 5>