Jvc LA 31 Service Manual

Page 2

A31

Contents

Page Page
1. Specification ................... . . L. . . . . . .1 6-(6) Motor RPM Adjustments ....... . ..... . .3
2. Names of Controls and Their Function . . . . . . . . . . .2 7. Block Diagrams ..... . ............. . ....... 8
3. Exploded Views and Parts List ....... . . , . . . . . . .3 8. Printed Circuit Board Ass'y and Parts List . . . . . . . . .9

3-H) Mechanism Assembly. . . . . . . . . . . . . . . . L .3 8-(1) TPS-300 Power Supply and LED P.C.

3-(2) Tonearm Assembly . . . . . . . ...... 5 Board Assy ......................... 9

3-(3) Mechanism Base ...... . .............. 5 8-(2) MC~942R Motor Driver P.C. Board Asty . . . .10
4. Operation of Automatic Mechanism . . . . . ...... . .6 9. Packing Materials and Part Numbers ..... . 11
5. Cartridge Replacement ...... . . . . . . . . . . . . . . . .6 10. Trouble Shooting . . . . . .................. 12
6. Adjustment Procedures. . . . . . . . . . . . . . . . . . . . . .7 .10-(1) When turntable operation is abnormal. . . . 12

6-(1) Overhang Adjustment. . . . ...... . . . . . . . .7 11.: L-A31 Schematic Diagrams. . . . . . . . . . . . . . . . . 14
' 6-(2) Anti-skating Adjustment. . . ..... . . . . . . . .7 12. Parts List with Specified Numbers for Designated

6-(3) TonearmLifterHeightAdjustment.........7 1Araa........ ..... 16

644) Auto-return (Lead-out) Adjustment . . . . . . . .7 13.Accessorias List. . . . . . . . . . . . . . . . . . . Back cover
' 6-(5) Tracking Force Adjustment. . . . . . . . . . . . . .7

WARNING! '

When replacing the parts marked with A , be sure to use the designated parts to ensure salety.

in either direction.

1. Specifications

MOTOR AND TURNTABLE

Motor: Coreless, DC type FG servomotor
,Drive system: Direct drive

Speeds: 33-1/3 and 45 rpm

Pitch control range: 13%

Less than 0.03% (WRMS). 0.015%
(WRMsl' 0.05% (DIN)

Wow and flutter:

Rumble: More than 75 dB (Dlltl-B)

Speed detection: integrated frequency generator

Platter: Aluminum ailoy die-casting

TONEARM

Type: T.H. (Tracing~Hold system. static
balance) Straight tubular arm

Eflectivc length: 220 mm

Tracking error: +3°35' -0°43

Overhang: 15 mm -

Tracking (orce range: 0 - 3 g (0.1 grams division, direct

' reading)

Weight range: 8.5 - 12 9

(including headshelkl)

CARTRIDGE (not provided on units for U.S,A.. Canada
and the U.K.)

MODE L: 2-18

Type: Moving Magnet (Cartridge body:
MD-1025)

Stylus: 0.6 mil. diamond (DT-ZlS)

Optimum tracking: 1.75 1 0.25 grams

force "

-. 2555

r CHECKING YOUR LINE VOLTAGE (For U.S. Military Market and Other Countries)
Belorc inserting the power plug, please check this setting to see that it corresponds
with the line voltage in your area. If it doesnt, be sure to adjust the voltage selector
swnch to the proper setting belore operating this equipment. The voltage selector
swrtch is located either on the set's on the chassis. Simply insert a screw driver into the
voltage selector switch and turn it in either direction while pressing slightly and in such
a way that desired voltage marked on the switch is positioned the arrow marked on the
rear panel or the chassis. The voltage selector switch accommodates up to three turns

Output:
Frequency response:
Separation:

Load resistance:
Compliance:

GENE HAL

Power Source:
Power Consumption:
Dimensions:

Weight (NET):

FEATURES

. 3 mV (lkHz, 5 cm/sec)

10 to 25,000 Hz

More than 25 dB (1 kHz)
(with test record TRS-l)

47 kilohms - 100 kilohms
10 x 106cm/dyne (Dynamic)
30 x 10'5cm/dyne (Static)

See page 16

See page 16

11.5(H) x 42(W) x 35.5(0) cm
(with cover closed)

(Since the dimensions show only
the design measuremen ts, consi-
deration is required when install-
ing the unit in a limited space such
as a rack.)
5.2 kg (11.4 lbs.)

(without corrugated cardboard
case)

DC type FG servomotor. Direct Drive tow-row stroboscope.
Oil-damaged cueing, Anti-skating mechanism, All front

operations.

'Measured at attached encoder's output by K 8; K measur-

ing method.

. ' 'Dasign and specifications subject to change with) no'DCG.