Adjustment Instructions - LG Multiplex 72 Service Manual

1. APPLICATION RANGE
These adjustment instructions is applied to MV-033A chassis.
2. Notes
2.1. Because this is a cold chassis, it is not necessary to use an
isolation transformer.
But operate it using a transformer between the power
supply line and chassis input to prevent electric shock and
to protect the test instrument.
2.2. All adjustment must be done in correct sequence.
However, for the better productivity, it can be changed in
pre-permitted range.
2.3. Environment conditions : If not specified, it must be done in
following conditions.
25cC ! 5 cC
1) Temperature :
: 65 % ! 10 %
2) Humidity
2.4. Power supply of a SET which is adjusted is AC110-240V,
50/60Hz.(EU model : AC230V,50HZ)
2.5. If not specified, the receiver must be operated for more
than 20 minutes prior to the adjustment.
2.6. Signal
Receive the standard color signal. (65dB ! 1dB uV)
LG standard signal means the digital pattern PAL-B/G
05CH.
3. DECK Line Adjustment.(VCR DECK Part)
AZIMUTH ADJUST SCEW AZIMUTH ADJUST SCEW AZIMUTH ADJUST SCEW
P2 P2 P2
DRUM DRUM DRUM
FE HEAD FE HEAD FE HEAD
P1 P1 P1
TENTION ARM TENTION ARM TENTION ARM
P0 P0 P0
SUPPLY SUPPLY SUPPLY
REEL REEL REEL
<Fig1> Adjustment Position
3.1. P2/P3 Pre-Adjustment
3.1.1. Necessary Instrument
1) PAL SP Normal TAPE
2) OSCILLOSCOPE
3) 10:1 PROBE : 2 PIECES
4) SPECIAL NUT DRIVER (for P2/P3 Control)
3.1.2. Adjustment
1) Play the PAL standard Tape(SP).
3-2

ADJUSTMENT INSTRUCTIONS

X-Value Fixed Screw
X-Value Adjustment Hole
P3 P3 P3
Tilt Adjustment screw
Height Adjustment Screw
PINCH - ROLLER
P4 P4 P4
T/UP ARM T/UP ARM T/UP ARM
CAPSTAN CAPSTAN CAPSTAN
TAKE - UP TAKE - UP TAKE - UP
REEL REEL REEL
2) Connect to J261(H/SW) the OSCILLOSCOPE(CH-1) on
the MAIN1 PCB.
3) Connect to J219(RF) the OSCILLOSCOPE(CH-2) on the
MAIN1 PCB.
4) With observing the RF envelope waveform, adjust P2, P3
until it becomes the waveform C.
5) Check the envelope waveform is in the maximum size by
pressing the TRK UP(+).
P2
<A> P2 POST ADJUSTMENT
P3
<B> P3 POST ADJUSTMENT
<Fig2> P2/ P3 Adjustment Waveform
3.2. CTL/AUDIO LEVEL ADJUSTMENT
3.2.1. NECESSARY INSTRUMENT
1. CTL TAPE
2. PAL SP Standard TAPE(for Audio level adjustment)
3. OSCILLOSCOPE
4. 10:1 PROBE : 2 PIECES
5. RMS METER(for Audio level adjustment)
3.2.2. CTL ADJUSTMENT
THIS ADJUSTMENT MUST BE DONE WHEN THE
UNCONTROLLED DECK IS WAREHOUSED.
1) Connect the OSCILLOSCOPE to J101(CTL)
2) After playing the CTL control tape, make sure the CTL
waveform range is From 1.5 :1 to 2.5 : 1.
If it is out of range , adjust CTL waveform to the following
procedures.
¤ If is over 2.5 :1, lower the head height.
After turning the height adjust screw counter-clockwise
to adjust its level from 1.5 : 1 to 2 : 1. Check the tape
location at P4. Readjust the TILT.(2:1)
¤ŁIf is under 1.5:1, heighten the head height.
After turning the height, adjust the screw clockwise to
adjust its level from 2 : 1 to 2.5 : 1. Check the tape
location of P4. Readjust the TILT.(2:1)
3) Play the standard tape and adjust the azimuth screw right
and left by using the oscilloscope and level-meter to
maximize the audio sound.
Adjust the azimuth screw & the height adjust screw at the
same time because they have mutual relationship.
(Check CTL again after the adjustment)
*A/C head adjustment order
Height adjust screw->check the TILT->azimuth screw->
check CTL
1 1 1
CTL WAVEFORM CTL WAVEFORM CTL WAVEFORM
D D
<C> The Waveform after adjustment
2 2 2
<Fig3>