Nakamichi 530 Service Manual

Page 1

Service Manual

Nakamichi

Nakamichi
530

Receiver

Page 2

CONTENTS

1, General .................................. 3
2. Principle of Operation ---------- 4
2. 1. Fundamental Circuits - - ~ 4
2.1.1. C-MOS IC ----------------- 4
(1) Features of C-MOS IC ' 4
(2) Gate Logic ........................................................... 5
(3) Gated Flip-Flop -------- 5
(4) Compatible C-MOS ICs - 5
2.1.2. Operational Amplifier IC ----- 6
(1) Voltage Follower Circuit ................................................. 5
(2) Amplifier Circuit ...................................................... 5
(3) Oscillator (Astable Multivibrator) .......................................... 6
(4) peak Holding Circuit ................................................... 7
2.1.3. Quadrature Detector . . . . . 7
2. 2. Power Mute Signal 8
2. 3. Tuner Section ........................ . . . . . 9
2.3.1. FM MPX Stereo Broadcasting Operation ........................................ 9
2.3.2. OperationofTunerSection------...-...................... ................ 10
2.3.3. Tuning System ........... 11
(1) Varicon Voltage .......................... ... 11
(2) Motor Drive Circuit and Frequency Sensor - .......... . . . 11
(3) Preset Tuning ......................................................... 12
(4) Station Detecting Circuit ................................................ 13
(5) Auto~Tuning ...................................... 13
(6) Tuning Indicator -------------------------------- 15
(7) FM Mute and Compulsion Mono - ................ 17
2. 4. Amplifier Section ............................................................. 18
2.4.1. Phono Eq. Amplifier -
2.4.2. Subsonic Filter ............................................................
2.4.3. Tone Control ..............................................................
2.4.4. Power Amplifier ................
(1) Pre-stage (Voltage Amplifier) - - -
(2) , Output Stage (Power Amplifier) .
(3) Limiter ................. , .............................................
2.4.5. Protector Circuit ...........................................................
3. Removal Procedures ....................................................................
3. 1. Top Cover ............................................................
3. 2. Bottom Cover . . . .
3. 3. Front Panel Ass'y . . .....
3. 4, Front-end Holder Ass'y
3. 5. Power Transformer ............................................................ 25
3, 6, Diode Bridge ................................................................ 25
3. 7. Power P.C.B. Ass'y and Heat Sink . . . . 25
3. 8. Pulley Holder B Ass'y and Pulley Ass'y ~ . . 25
3. 9. Front Chassis Assy ---------------- . . . 25
3. 10. Scale Holder Assy ............................................................ 25
3. 11. Lamp House Cover Ass'y and Lamp P.C.B. Ass'y ------------------------------------- 26
3. 12. Tuning Lamp P.C.B. Ass'y .................. 25
3. 13. Indicator P.C.B. Ass'y --------- - - - 26
3. 14. Tuning Control Switch Ass'y .................................................... 27
3- 15. Auto-Tuning P.C.B. Assy, Preset Volume P.C.B.
Ass'y and Preset Switch P.C.B_ Ass'y .............................................. 27
3. 16. Power Switch ................................... 27
3. 17. Main P.C.B. Ass'y and Function P.C.B. Ass'y ............... . . . 27
3. 18. Headphone Jack ...................................... . . . 27
3. 19. Rear Panel Ass'y .................................................... 27

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turned ON and 0305 is turned ON. Accordingly, electric
current passes Tuning Motor via 0309 and 0305, as a
result Tuning Motor starts driving so that the Tuning
Pointer will move to the left-hand side on the Dial Scale.
On the other hand, when REF Voltage is grounded
through R391, the output of |C307(2/2) becomes 0 V, as
a result 0308 is turned ON, 0303 is turned OFF and
0304 is turned ON. Accordingly, current passes Tuning
Motor via 0304 and 0308, as a result Tuning Motor will
rotate to move the Tuning Pointer to the right-hand side.

2) Station detected

While the Tuning Motor is driving as referred to in above
1), when a station is detected as per (4) "Station
Detecting Circuit", the base voltage of 0310 turns from L
to H, as a result 0310 is turned OFF. When 0310 is
turned OFF, a differential L pulse is generated at Reset
m Signal through C339, as a result Auto LT and RT
Flivalops are reset through D316 and D315. Therefore,
D309 and D310 are turned OFF, accordingly, only AFC
and REF voltages are connected to the inputs of
lC307l2/2) in the Tuning Motor Drive Circuit.

In case the difference of input levels to lC307(2/2)
becomes nil, i.e., AFC Voltage becomes equal to REF
Voltage, Tuning Motor will stop its rotation, thus auto-
tuning is now completed.

3) Automatic Scanning Switch pressed continuously
When Automatic Scanning Switch Left or Right is kept
being pressed, its activation would be as follows:

When a station is detected while auto-tuning, the base
We of 0310 becomes L from H. At this time W
PUIse=L is pulse-likely output to the reset input of Auto
LT/RT Flip-Flop. As a result, Auto LT/RT Flip-Flop is

{so

Auto
Tuning

L.

0311
u
r-

reset momentarily, but it is set again since Automatic
Scanning Switch is kept being pressed, thus auto-tuning is
continued.

(b) Auto-Return

Auto-return to left end (Minus Return Signal) or right end
(Plus Return Signal) will be conducted respectively by
VR002 or VR001 in the Preset Switch P.C.B. Assy.

In an ordinary case, the stations to be selected exist
between these ends.

If Automatic Scanning Switch is further pressed to the
direction where there should be no station, Tuning
Pointer will reach either left or right end of the Dial Scale.
When it reached either right or left end, Tuning Motor will
change its direction, therefore the direction of auto-tuning
will be automatically reversed and auto-tuning will be
continued until a station is detected. When detected,
Tuning Motor stops there.

lC305-2 and l0305-5 are provided with Minus Return
Signal and Plus Return Signal, each determining left end
or right end respectively. When the Varicon Voltage
exceeds Minus Return Signal or Plus Return Signal level,
lC305-1 or |C305-7 will become L respectively.
Accordingly, if Auto LT Flip-Flop is set, lC305-1 will
become L when Varicon Voltage exceeds Minus Return
Signal, as a result, Auto LT Flip~Flop is reset and Auto
RT Flip-Flop is set simultaneously via D313, thus the
auto-tuning direction will be reversed.

On the other hand, if Auto RT Flip-Flop is set, |C305-7
becomes L when Varicon Voltage exceeds Plus Return
Signal, as a resmt Auto RT Flip-Flop is reset and Auto LT
Flip-Flop is set simultaneously via D314, thus the
auto-tuning direction will be reversed.

R390 55K R350 330K

-"\N\1-<-() AFC

R391 66K

R351 330K

O REF

1 -0 Reset Pulse

® Remm Signal 0

Voricon Vollage o->-<

3
4 D313
@Retum Sienul 0-»-

Avie/Preset
Switch

Autc

P reset I
Aura l
l . 0

Turning Motor
orive Circuit

~J

Preset Voltage 0

Preset

Fig. 2.3.11 Auto-Tuning Circuit

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Page 33

STEP ITEM OUTPUT CONNECTION MODE ADJUSTMENT REMARKS
1. Connect the FM Generator to the 300-ohm Balanced Terminals of the N-530.
2. Set the frequency of the FM Generator to 98 MHz. (Refer to the preceding
explanation for the frequency to be set.)
3. Set N-530 to the initial mode (see MODE).
Preliminary Steps N-530 Initial Mode: Function - FM 4. Signal modulation is performed by adjusting the Signal Output VFl of the
1 for Adjustment Hi-Blend - OFF M17003 Distortion Measurement System. The modulation rate is indicated
Audio Mute - OFF by the meter on the M1000A FM Generator. 3
5. Test Points: TF-i, TF-2 and TP-3 on the Main P.C.B.
. 6. Inhibit the AFC function by shorting between TP-G (source) and TlP7 (drain)
5 of PET 0301 on the Main P.C.B. ;
1 After completion of Tuner Adjustment, remove the short of 0301.
FM Generator: Function - D.S. (Dual Sweep)
Oscilloscope to Frequency - 98 MHz 1. Select Station A by depressing the Station Memory Switch A.
2 S-Curve Alignment Test Point TP-1 Sweep Width - 600 kHz 2. Turn the Station Preset Control A to obtain correct S-curve waveform
RF Level - 1 mV (300 n) 65 dBf (whose width "a" and "b" are equal) as shown in Fig. 4.1.4.
N-530: Mode - Mono
1. Do not turn the Frequency Dial on the FM Generator and Station Preset
Distortion Meter to Control A of the N-530.
Dc Balance Adjustment RECORDING OUTPUT Jacks FM Generator: Function - CW/Stereo Main P.C.B. . 2. With Function SWitch of the FM Generator set to CW, adjust L304 to obtain
3 Distortion Adjustment (Mono) Oscilloscope between RF Level - 1 mV (300 n) 65 dBf Quadrature Coils 0 V DC level (Within 1- 5 mV) on the Oscilloscope.
TP-2 and TP-3 N530: Mode - Mono L303, L304 3. With Function Switch set to Stereo, adjust L303 to obtain minimum
distortion.
FM Generator: Function - Stereo . , .
Frequency _ 98 MHz (See note.) Front-end 1. Adjust coll-T1 and TrimmerTCA to obtain 3%- or less distortion. .
RF Level _ 2.2 11V (300 0) Col) T1 2. If a distortion of 3% or less is unable to be achieved, adjustment of coil T301
4 Sensitivity Adjustment of Oscilloscope and Distortion Meter Input Selector - EXT. Trimmer TCA, and semi-fixed volumes VR301 3", V3302 M" be necessary.
Front-end tci RECORDING OUTPUT Jacks M17003: osc. - 1 kHz, Level 100% TCR1, TCRZ 3- 'f a ét'SaCW "95" '5 "0 meme '" we We 2' adlusmer"
(Signal Modulation rate: 100%) Main P.C.B. 4 oAerimmers; T'CR :nddTCR2 2 be necesIsIary. b TP 8 l )
Switch Box: L + R T301,VR301, VR302 . er comp etion o a justmen , remove s orting etween - source
N-530: Mode- Mono and TP-7 (drain) of PET 0301 on the Main P.C.B. (AFC. ON).
FM Generator: Function - Stereo 1. With the Pilot Test Switch on the FM Generator depressed, adjust the
Frequency - 98 MHz (See note.) pilot level to obtain 80% (pilot signal modulation rate: 7.2%) on the meter
RF Level - 1 mV (300 n) 65 dBf of the FM Generator.
. Pilot Level - 0 Main P.C.B. 2. Adjust VR304 so that the Stereo Lamp will light up.
5 59 Lamp Admme" Input Selector - EXT. veso4 As the lamp is illuminated in a certain range of VR, VR304 shDUId be fixed
M17008: OSC. - 1 kHz, Level 100% approximately at the center of that range.
Switch Box: L + R 3. Depress the Mono Switch and set to Mono mode, then make sure that the
N-530: Mode - Stereo Stereo Lamp goes out.
FM Generator: Function - Stereo
Frequency - 98 MHz (See note.)
l - n f . .
Eli-:29. _1 $X$é300 55 dB Main P.C.B. Adjust T301, VR301, VR302 and T1 to obtain 0.2% or less distortion.
5 Distortion Adjustment AC Voltmeter and Distortion Meter (Pilot Si nal Modulation rate' 9%) T301, VR301, VR302 If the above value does not comply with the specified one, stricter readjustment
(Stereo) to RECORDING OUTPUT Jacks Input Seéiector _ EXT Front-end starting from step 3 DC Balance Adjustment and Distortion Adjustment (Mono)"
M17003: osc. - 1 kHz, Level 100% mm '5 "ecessarv'
Switch Box: L l
N-530: Mode - Stereo i
FM Frequency: Function - Stereo
Frequency - 98 MHz
RF Level - 1 mV (300 Q) 65 dBf
' I - ° .
7 Adjustment of AC Voltmeter to fr::;tl:;:cto: 30:). Main P.C.B. Adjust VR303 for the left channel with Switch Box "L" and for the right
Recording Output Level RECORDING OUTPUT Jacks M17003: OSC. _ 400 Hz, Level 50% VR303 channel With SWItch Box R to obtain 225 mV on the AC voltmeter.
(Signal Modulation rate: 50%)
Switch box: L/R
N-530: Mode - Stereo

Note: Do not turn the Frequency Dial on the FM Generator and Station Preset Control A of the N-530.

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