Fisher AD 823 Service Manual

Page 2

CONTENTS

Specifications ..................................................................................... 3
Functional Block Diagram ........................................................................ 4
Safety Certification ................................................................................ 5
Laser Beam Radiation Spot ....................................................................... 5
Disassembly Instructions ....................................................................... 6,7
Cabinet & Chassis Exploded View .. c. .. 8,9
Cabinet & Chassis Parts List ................................................................... 10
Mechanism Exploded View ...................................................................... 11
Mechanism Parts List ............................................................................ 12
Adjustment Procedures ............................................... 13,14,15,16,17,18,19,20
P.C.Board Alignment Points ..................................................................... 21
Installation Method for Each Leaf Switch ...................................................... 22
input Port Assignments .......................................................................... 23
Output Port Assignments .......... .. .. ... 23
System Block Diagram 8. Pin Location ......................................................... 24
Printed Circuit Board (Bottom View) ....................................... 25,26,27,28,29,30
P,C.Board Parts List .............................................................. 31 ,32,33,34,35
Safety interlock ................................................................................... 36
Point to Point Wiring Diagram ............................................................... 37,88
Schematic Diagram .............................................................. 39,40,41,42,48
IC Signal Flow& EquivalentCircuit ................................................ 44,45,46,47
Semiconductor Lead Identification ............................................

Page 4

£5582 52;:

a. :3

FUNCTIONAL BLOCK DIAGRAM

Page 7

DISASSEMBLY INSTRUCTIONS (Continued)

REMOVING MECHANICAL ASSEMBLY REMOVING SERVO P.C.BOARD
1. After removing the front panel, disassemble the shaft of the 1. After removing the mechanical assembly. disassemble the
power switch, Servo P C. Board by removing the two mounting screws. (No.

24 25) Ifnecessary. unsolder the leads
2. Disassemble the mechanical assembly by removing the four

mounting screws fixing it. (No. 14 ~ 17)

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REMOVING CONTROL P.C.BOARD
1. After removing the front panel, disassemble the control
board by removing eight mounting screws fixing it.

REMOVING MAIN P C. BOARD
After removing the mechanical assembly, disassemble the
Main P. C. Board by removing the six mounting screws fixing
it (No 18 ~ 23)

c) The mechanical assembly and the front panel have been
removed.

Lil;3 PEI-nI-I <

Page 17

ADJUSTMENT PROCEDURES (Continued)

Starting Point
Adjusting Screw

I/I/I/I/fl/I/[I/I/I/Il/I/III/I/Ill//lll//I///l/l////I/

2. Load the test disc YEDS4 on the turntable With the VR605 at
the center point.

3 Connecting thte following low-pass filter to the focus coil
test terminal, connect them to a DC voltmeter and an
Indication 7 (Gap of Leaf Switch) oscilloscope.
1.2 7 (0mm) 1.3- (0.1mm) 14 7 (0.2mm) 1,5 7 (0.3mm)
IJC VTVM and

Oscilloscope

J

4 Turning on the power. play the first tune of the disc

FOCUS COIL
TEST TERMINAL

220/16

220/16

5. After checking the voltmeter for reading, adjust the height of
the turntable for a reading of 0V i0.25V. (When the figure of
the volt meter shows ",+ move up the turntable and when it
shows 7 move it doun. In this circuit, it moves by 0.85mm

12. ADJUSTING HEIGHT OF TURNTABLE Der 1V.)

When the motor is replaced, this adjustment is required.

1. Install the turn table as the height from the chassis to the 13- ADJUSTING FOCUS / TRACKING GAIN_
lower end of me mmtabje is 21.5mm. The following circuits for measuring is required for adjusting the

focus gain and the tracking gain accurately. if this circuit is not

available, adjust them by using the plain adjusting method

18K 10K .
w 35 Signal
10K Generatnr
M

10K I0 0047
INC M s -~w-j --ox
\7
5 VOK 0047
/ 1
10K 10K 10K 10K rev 0047
Wfi-II OY
10K "0047
UUTC l

I IC LA645800requivaient

- In advance, adjust the semiAfixed volume (2K3) or the
minimum output at the OUT, by shorting across IN and SG,
and by applying i kHz, 1Vp-p from 8G.

_17_