Fisher AD-530 - Adjustment Procedures (Continued); Gain, Height, and Jitter Adjustments

ADJUSTMENT PROCEDURES (Continued)
and test terminal (CN12-1) TOFF pin to GND to turn
tracking servo OFF.
2. Connect a DC Voltmeter and an oscilloscope via the low-
pass filter like that shown in the illustration below to the
test terminal (CN12-3) TE (tracking error) pin.
22K
E —w———_—-
qT [. Our. DC Voltmeter
ee f
an
220/16 =;
GND I GND Oscilloscope
Measurement circuit
4. Adjust P203 so that the DC Voltmeter reading is minimum
(oscilloscope waveform is symmetric to + and — about
the zero level).
CONFIRMING JITTER
If no jitter counter is available, this check does not have to be
have to be performed.
1. PLAY the fourth item on the test disc (Modern Wave I).
2. Connect an oscilloscope to the test terminal (CN10-3) HF
pin, and check that its level is in the range 2.0Vp-p ~
3.3Vp-p.
3. Connect a jitter counter to test terminal (CN11-4) EFM pin,
and check that the 3T jitter value is less than 20ns.
(Window width: 600ns ~ 850ns, Set Level: 2.5V)
4. Now PLAY the tenth item on the test disc and check that
the jitter value is less than 20ns again.
ADJUSTMENT OF TURNTABLE HEIGHT
This adjustment must be performed when the Spindle Motor
is replaced.
The turntable should be mounted so that its upper surface
is 14.05mm+0.1mm above the surface of the chassis.
Turntable
14.05mm
Chassis
Spindle
Motor
Place the test disc (Modern Wave II) on the turntable.
Connect a DC Voltmeter and an oscilloscope via the low-
pass filter shown below to test terminal (CN9-5) F (focus
coil) pin.
aah OUT 1
i 920/16 [. | DC Voltmeter
and
akin reed eNb | Oscilloscope
Measurement circuit
Apply Power Switch to the set and PLAY the first item on
the disc.
If the DC Voltmeter reading is not in the ranges 0V+0.2V
for inner tracks and 0V+0.35V for outer tracks, then the
turntable height must be readjusted. Raise the turntable
higher if the DC Voltmeter indicator is on the plus (+)
side, and lower it if it is on the minus (—) side.
(With this circuit 1V represents movement of approxi-
mately 0.55mm ~ 0.65mm.)
ADJUSTMENT OF FOCUS/TRACKING GAIN
The measurement circuit diagrammed below must be used in
order to adjust focus gain and tracking gain correctly.
soc [=
18K
‘ 18K
1 '
2 ? IN 10K
Main P.C.B. + ; ae OQ '
{
CN2
5
:
3
ee
6 t
;: 2
Tracking ane C22
Gain:
{
'
'
'
'
i]
‘
4
es.
tos
t s
4
Focus Gain:
PICK UP > 2
CN2
Measurement circuit
10K
Use IC TA7256P or an equivalent product.
Short the interval between IN and SG, apply 1kHz, 1Vp-p
from SG, and adjust variable resistor 2kQ-B so that the
OUT output is minimum.
10K
s¢_
Signal
Generator
10K
10K 0.047
w— X
10K 0.047
I Oualtrace
Oscilloscope
10K 0.047
0.047
10K i
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