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DISASSEMBLY
PROCEDURES (REFER TO PAGES 5 AND 18)
1|CABINET TOP REMOVAL
Remove 6 screws @ and then remove the cabinet top.
(2) FRONT PANEL ASSEMBLY REMOVAL
1, Remove the cabinet top. (Refer to step [1] .)
2. Pull off Volume,
Bass, Treble and Balance knobs
(105 and 146).
3. Remove 6 screws © and then remove the front panel
assembly.
TUNER P.C. BOARD (PCB-2) REMOVAL
1, Remove the cabinet top. (Refer to step
)
2. Disconnect J302, J303 and J351 from P302, P303
and P351 on the tuner P.C. board (PCB-2).
3. Open the lid of connectors (P301, P352 and P353) on
the tuner P.C. board (PCB-2) and then disconnect
the lead wires.
4. Remove
6 screws @ and then remove the tuner
P.C. board
(PCB-2)
with
back plate (136), shield
plate (172) and brackets (181 and 252).
[4] PHONO EQUALIZER P.C. BOARD (PCB-3)
REMOVAL
1. ao
the tuner P.C. board (PCB-2). (Refer to step
2, Remove 8 screws ® and then remove the phono
equalizer P.C, board (PCB-3) with MC amp. P.C. board
({PCB-4) and holder (198). At this time, open the lid
of connectors (P601, P602, P603, P604, P605 and
P801) on the phono equalizer P.C, board (PCB-3) and
then disconnect the lead wires and unsolder the lead
wires from phono equalizer P.C. board (PCB-3).
CIRCUIT DESCRIPTION
[1] MUTING CIRCUIT
The muting control voltage is taken out from (2 pin of
1C201 and then fed to the base of O205. At the weak
station or detuned point, the (2 pin becomes high level,
Q205 becomes low, 0357 is tuned off, NAND 1IC352 is
tuned to low, 0360 is tuned to on, 0361 (left channel)
and Q362 (right channel) are tuned to on and muting
operation is completed.
[2] SYNTHESIZER SECTION
1) FM
The output of local oscillator in the front-end is fed to
® pin of the pre-scaler 1C701 and then divided by 30 or
32 and fed to @7) pin of the PLL synthesizer 1C702.
The standard quartz oscillator output (4.5MHz) is divid-
ed by 180 in 1C702 and 25kHz standard signal is got.
The divided local oscillator output is compared with the
25kHz standard signal in the phase comparator.
When
the divided local oscillator frequency is higher
than standard frequency, @8) pin of IC702 becomes high
level but when it is lower, 85) pin of 1C702 becomes low
level. When the both frequencies are equal, @8) pin be-
comes floating.
@® pin output of 1C702 is fed to the vari-cap diode of
the front-end through L.P.F. (Q702, 0703, Q712) and
controls
the frequency
of VCO
(local oscillator fre-
quency).
2) AM
The local oscillator output of AM 1C251 is fed to
pin
of the PLL synthesizer C702 and divided. The standard
quartz oscillator output (4.5MHz) is divided by 450 in
1€702 and 10kHz standard signal is got. The divided
local oscillator output
is compared
with
the 10kHz
standard signal in phase comparator.
(5) POWER OUTPUT P.C. BOARD (PCB-1) REMOVAL
1. Remove the phono equalizer and MC amp. P.C. boards
(PCB-3 and PCB-4). (Refer to step 4.)
2. Remove 5 screws @ and 2 shafts (242) and then
remove the power output P.C. board (PCB-1), At this
time, open the lid of connector (P401) on the power
output P.C. board (PCB-1) and then disconnect the
lead wires and unsolder the lead wires from power
output P.C. board (PCB-1).
(6) SPEAKER
SWITCH
AND
SPEAKER
TERMINAL
P.C. BOARDS (PCB-11 AND PCB-12) REMOVAL.
1, Remove the front panel assembly and power output
P.C. board (PCB-1), (Refer to steps (2) and 5 .)
. Remove 3 screws
@ and then remove the panel back
assembly (104) and the panel (140).
Remove 4 screws © and then remove the bracket
(253).
. Pull off the 2 push button assemblies (109).
. Remove
2 screws @ and then remove the speaker
switch
and speaker terminal
P.C. boards
(PCB-11
and PCB-12) with bracket (183). If necessary, un-
solder the lead wires.
PR
WON
Z TONE CONTROL P.C. BOARD (PCB-5) REMOVAL
. Remove
the speaker
switch
and speaker
terminal
P.C. boards (PCB-11 and PCB-12). (Refer to step 6] .)
2. Remove
3 hexagon
nuts @ and 2 screws @ and
then remove the tone contro! P.C. board (PCB-5). At
this time, open the lid of connector (P501) on the
tone control P.C, board (PCB-5) and then disconnect
the lead wires and unsolder the lead wires from tone
control P.C. board (PCB-5)..
[3] PRESET MEMORY
1) Memorizing
When wr) of the preset keys, M1 to MB is depressed, one
of the 2 to 49 pins of IC702 becomes high level. The
displayed frequency is memorized into the memory
(RAM) with correspond to the depressed key,
2) Recalling
When one of the preset keys, M1 to MB is depressed, the
contents of the memory (frequency) is recalled.
[4] FM/AM STATION SCANNING
1) When tuning mode switch is set to AUTO
When the UP key is depressed, the frequency rises at saw
tooth wave mode and when DOWN key is depressed, the
frequency falls. When the high level input is fed to stop
terminal ( 3) pin of C702), the scanning is stopped.
2) When tuning mode switch is set to MANUAL
Whenever UP or DOWN key is depressed once, the fre-
quency rises or falls by one step (channel space).
[5] OVERLOAD PROTECTION (LEFT CHANNEL)
As soon as the current over rated power flows, the vol-
tage between both emitters of 441 and 0443 rises, Q9,
Q8 and Q7 are turned to on, Q1 is turned to off. So O3
(schmit trigger circuit) is tuned to off. The gate of Q401
becomes
OV and Q401
is turned to on. The input to
power amp. is cut and 0417 is turned to off, So the
Operation of pre-driver, driver and power stages stops
and the circuit is protected.
€
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