Harman Kardon CD491 - Page 4

DISASSEMBLY PROCEDURES (REFER TO PAGES 17, 18, 19 AND 30)
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CABINET TOP REMOVAL.
Remove 6 screws @ and remove the cabinet top.
FRONT PANEL ASSEMBLY (103) REMOVAL
1, Remove the cabinet top. (Refer to step [1] .)
2. Pull off Master Fader, Output Level, Mic. Level
and Rec. Level knobs (105 and 152).
3. Remove 6 screws © and remove the front panel
assembly (103).
LOGIC CONTROL P.C.BOARD(PCB-2) REMOVAL
1. Remove the cabinet top. (Refer to step [1] .)
2. Disconnect J801, J802, J803, J808 and J809
from P801, P802, P803, P808 and P809 on the
logic control P.C. board (PCB-2).
3. Open the lid of connectors (P804, P805, P806
and P807) on the logic control P.C. board (PCB-2)
and disconnect the lead wires.
4. Unsolder the lead wires connected to the logic
control P.C. board (PCB-2).
5. Remove 4 screws @ and remove the logic
control P.C. board (PCB-2) with heat sink (301),
PUSH SWITCHES P.C.BOARD(PCB-4) REMOVAL
1, Remove the cabinet top. (Refer to step [) .)
2. Open the lid of connectors P451, J803, P804
and P401) on the main, logic control and VR
P.C. boards (PCB-1, PCB-2 and PCB-3) and
disconnect the lead wires.
3. Remove 3 screws ®and remove the push
switches P.C. board (PCB-4) with rec. cal P.C.
board (PCB-9). If necessary, unsolder the lead
wires.
MAIN P.C. BOARD (PCB-1) REMOVAL
1, Remove the front panel assembly, logic control
P.C. board (PCB-2) and push switches P.C. board
(PCB-4). (Refer to steps [2] through I .)
Disconnect J501 and J503 from P501 and P503
‘on the main P.C, board (PCB-1).
3. Open the lid of connectors (P201, P202, P251,
P301, P502, P551 and P601) on the main P.C.
board (PCB-1) and disconnect the lead wires.
4, Unsolder lead wires connected to the main P.C,
board (PCB-1).
5. Remove 2 screws @and remove the tape
monitor switch (SW406).
6. Remove 8 screws @ and remove the main P.C.
board (PCB-1).
La
cout DESCRIPTION
@ MPX/DOLBY NR CIRCUIT
The MPX filter circuit is turned on and off by the
MPX filter switch. When it is off, the signals bypass
the circuit. The dolby circuit is turned on and off by
the dolby NR switch, and selected B and C types by
the dolby NR type selector. When the circuit is on
and type selector is B position, B-type dolby
equalization is applied so that the signal is compress-
ed during recording and expanded during playback.
MUTING
. PLAYBACK MODE
When the play button is pressed, the muting signal for
the playback mode (which cuts the recording signal)
is output from () pin of the 4 bit micro computer
1C851 and applied to Q701 (left channel) and Q702
(right channel). This turns on Q701 and Q702 to
mute the recording signal.
2.
3.
VR P.C, BOARD (PCB-3) REMOVAL
1. Remove the front panel assembly. (Refer to step
2.)
2, Remove 6 screws @ and remove the cabinet
bottom assembly (102).
3. Remove 4 hexagon nuts @ mounting the VR
P.C. board (PCB-3) and remove it.
CASSETTE TAPE RECORDER MECHANICAL
ASSEMBLY (113) REMOVAL
1, Remove the front panel assembly and logic
control P.C. board (PCB-2). (Refer to steps (2)
and (3) .)
2. Remove 4 screws @ and remove the cassette
tape recorder mechanical assembly (113) with
plate assembly (104) backward.
PLATE ASSEMBLY (104) REMOVAL
1, Remove the cassette tape recorder mechanical
assembly. (Refer to step [2 .)
2. Remove 2 screws @ and remove the plate
assembly (104).
DIRECT DRIVE MOTOR (506) REMOVAL
1, Remove the plate assembly. (Refer to step
2. Remove 2 hexagon nuts @
direct drive moto?.
lead wires.
)
and remove the
If necessary, unsolder the
PAD ASSEMBLY (505) REMOVAL
1, Remove the plate assembly. (Refer to step 5} .)
2, Remove 2 screws @ and remove PAD assembly.
If necessary, unsolder the lead wires.
IDLER MOTOR ASSEMBLY (503) REMOVAL
1, Remove the direct drive motor. (Refer to step
)
2, Remove 2 lock washers ({) and remove supply
and take-up reel spindle assembly (508 and 509).
At this time, remove the belt (511) and spring
(507).
3. Remove 3 screws @® and remove the idler motor
assembly.
HEAD BASE ASSEMBLY (502) REMOVAL
1,
Remove
the
direct
drive
motor.
(Refer
to
step
)
2. Remove 2 E-stop rings ® and remove supply and
take-up pinch roller assembly (516 and 513).
3. Remove the lamp holder assembly (519) and
lamp holder mounting bracket.
4, Remove 2 E-stop ring @ and remove head base
assembly with record/playback and erase heads.
RECORDING MODE
When the record button is pressed, the muting signal
for the record mode (which cuts the playback signal)
is
output
from
@
pin
of
1C851
and
applied
to
091
(left channel) and Q92 (right channel). This turns on
Q91 and 092 to mute the playback signal.
LINE MUTE (POWER SWITCH ON/OFF)
When the power is turned on, 051 is turned on for a
few seconds. At the same time Q93 and Q94 go on.
@ pin of the 4 bit micro computer 1C851 becomes
high level. The computer is reset. At the same time
Q91 (left channel) and Q92 (right channel) are turned
on. Thus, no shock noise is output to the OUTPUT
terminals.
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