Service Manuals, User Guides, Schematic Diagrams or docs for : LG Audio FL-R888K FL-R88~2
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ADJUSTMENTS
This set has been aligned at the factory and normally will not require further adjustment. As a result, it is not
recommended that any attempt is made to modificate any circuit. If any parts are replaced or if anyone tampers -
with the adjustment, realignment may be necessary.
1. TEST & ADJUSTMENT POINT
PNS02
Figure 1. Main l?C.Boatd
-
2. FOCUS & TRACKING GAIN ADJUSTMENT JIG
(TO SCOPE)
I
800H12Vrms -r
fa
1 RF0
TEO
osc 4
TEI
3
Vref Vref
2
4 FEI
FE0
CH2
(1 VIDIV)
Vref
CHI
(SOmWDIV)
" _
.`PK .6..8.~
NOTE) This jig is not serviceable pat?.
7
3. Before adjusting, preset adjustment potentiometers VR501, VR502, VR503 and VR504
center.
L
4. TRACKING BALANCE ADJUSTMENT .s`
1) Connect the oscilloscope to TP504 (pin @ : TEO) and TP504 (pin @ : Vref).
2) Insert the test disc (YEDS-18) and playback the 12th selection.
3) Turn VR502 fully counter-clockwise.
4) Adjust VR504 so that the amplitude above and below the zero DC line becomes equal (amplitude A=B).
A=B
5) Set VR502 to center position.
5. FOCUS OFFSET ADJUSTMENT (you have to use 1O:l probe)
1) Connect the oscilloscope to TP504 (RFO) and TP504 (Vref).
2) Adjust VR501 so that eye pattern becomes clear and waveform (Vp-p) is maximum.
3) Confirm the oscilloscope reading.
i ) Less than 200mV - OK
ii ) More than 200mV - readjust VR501 200mV.
Good adjustment d adjustment
EYE PATTERN
6. FOCUS, TRACKING GAIN ADJUSTMENT (with Jig)
1) Connect the gain adjustment jig to TP504.
2) Connect the audio frequency oscillator the A.F.OSC terminal on the gain adjustment jig.
Set the audio frequency oscillator output to 800Hz 2Vrms.
3) Set the gain adjustment jig with oscilloscope to below.
i ) CHl : SOmV/div, AC mode
ii ) CH2 : lV/div, AC mode
6-V FOCUS GAIN ADJUSTMENT
Set switch SW2 on the gain adjustment jig to position `lF".
Adjust VR503 so that the waveform on the oscilloscope looks as shown below.
Good adjustment Bad adjustment Bad adjustment
(Optimum focus gain) (Low focus gain) (High focus gain)
8
6-2) TRACKING GAIN ADJUSTMENT
Set switch SW2 on the gain adjustment jig to position "T".
Adjust VR502 so that the waveform on the oscilloscope looks as shown below.
Good adjustment Bad adjustment Bad adjustment
(Optimum tracking gain) (Low tracking gain) (High tracking gain)
7. FOCUS GAIN ADJUSTMENT (without Jig)
1) Connect a oscilloscope to PN502 (FAC 6) and PN502 (FAC @).
2) Insert test disc (YEDS-18) and put unit into play mode on track.
3) Adjust VR503 so that the waveform on the oscilloscope becomes like below.
-
2mS/div.
O.SV/div.
DC Mode
about 800mV - ov
1
-
8. TRACKING GAIN ADJUSTMENT (without Jig)
1) Connect a oscilloscope to PN502 (TAC @) and PN502 (TAC 8).
2) Insert test disc (YEDS-18) and put unit into play mode on track.
3) Adjust VR502 so that the waveform on the oscilloscope becomes like below.
-
0.5mSldiv.
( O.SV/div.
DC Mode
about 400mV - ov
I
WAVEFORMS OF MAJOR CHECK POINT
1% HF signal (RF signal) waveform (Test Point 2. EFM signal (pin NO. 32 of IC502, waveform during
TP504) during normal play. normal play.
2VIDiv.
( O.SV/Div.
500mWDiv.
( 500mS/Div.
3. Focus Coil Drive Waveform 8 Focus coil drive waveform (pin NO. 26, 27 of
(pin NO. 26, 27 of IC503) IC503) and FOK (pin NO. 33 of IC502)
8 When focus search failed or there is no disc When focus search is accomplished.
on the tray.
-0v
(CHl)
- ov
0-Q)
CHl :FOCUS COIL DRIVE SIGNAL
2VlDiv.
CH2 : FOK
4. Tracking coil drive waveform (pin NO. 3 of IC503) and TEO during Track traverse
1
(1) When time division is 20mS/Div. (2) When time division is 0.5mS/Div. (During
CHI :-TEO CHl :TEO
1V/Div. 1V/Div.
CH2 :TRACK COIL DRIVE SIGNAL CH2 :TRACK COIL DRIVE SIGNAL
2V/D iv. 2VlDiv.
(3) When time division is O.SmS/Div. (During 5. Feed motor drive waveform (pin NO. 10 of IC503)
backward track traverse) During normal play.
( 0.5VIDiv.
500mS/Div.
- ov
- ov
V-Q)
CHl :TEO
1V/Div.
CH2 :TRACK COIL DRIVE SIGNAL
2VlDiv.
10
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