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Transcript
Service Manual Nakamichi Nakamichi 620 power amplifier CONTENTS 1. 2. 3. General Principle of Operation 2. 1. Power Supply 2. 2. Power Block Pre-stage 2. 3. Power Block Output Stage 2. .4. Peak Power indicator Removal Procedures 3. 1. Cabinet Ass'y 3. 2. Rear Panel Ass'y 3. 3. Lamp 3. 4. 4. 5. 6. 7. 3. 9, 10, 11. Switch 3. 5. Power Block Ass'y 3. 6. Jack 3. 7. Indicator P.C.B. Ass'y 3. 8. Relay P.C.B. Ass'y and Cement Resistor 3. 9. Diode and Output P.C.B. Ass'y 3.10. Transformer and Capacitor Readjustment of Power Block Mounting Diagram and Parts List 5. 1. • Power Block Ass'y 5.1.1. Power Block P.C.B. Ass'y 5.1.2 Power Transistor P.C.B. Ass'y 5. 2. Output P.C.B. Ass'y 5. 3. indicator P.C.B. Ass'y 5. 4. Indicator Sw. P.C.B. Ass'y 5. 5. Indicator Lamp P.C.B. Ass'y 5. 6. Power Lamp P.C.B. Ass'y 5. 7. Relay P.C.B. Ass'y Mechanism Ass'y and Parts List 6. 1. Synthesis (A01) 6. 2. Mechanism Ass'y (B01) 6. 3. Cabinet Ass'y (B02) 6. 4. Main Chassis Ass'y (C01) 6. 5. Front Panel Ass'y (C02) 6. 6. Rear Panel Ass'y (C03) 6. 7. Indicator Lamp Ass'y (C04) 6. 8. Power Lamp Ass'y (C05) Wiring Diagram Performance Data Block Diagram Schematic Diagram Specifications 2 3 3 3 4 6 7 7 7 7 7 8 8 8 8 8 9 10 11 11 11 11 11 13 13 13 14 14 15 15 16 17 18 19 19 20 20 21 22 23 24 26 f ) 1 * I ) | V • 1. GENERAL Nakamichi 620 control functions are shown below. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Peak Power Indicator (L ch) Peak Power Indicator (R ch) AC Power Indicator Power Switch Power Indicator Threshold Selector Switch (High) Power Indicator Threshold Selector Switch (Low) Fuse Voltage Selector Output Terminals input Jacks Fig. 1.1 Fig. 1.2 CAUTIONS The Nakamichi 520 incorporates iarge capacitances. it is very dangerous to access the capacitor for a duration of about 3 minutes after ihe power switch has been turned off because of incompiete discharging. Use extreme care when accessing the capacitor for repair purposes. Never short the capacitor terminals with a screwdriver or a similar tool after the power switch is turned off, with an attempt to discharging the capacitor. (Shorting the terminal in such a way can meit the shorted point leading to a hole, and will give adverse effects on the capacitor itself.) The recommended way :o discharge the capaciior as quickly as possible is to turn off the power suppiy with sound emitting through the loudspeaker or to discharge the capacitor with resistances of 10012 — 300H, approx. 20W. Voltage Selector Change pverto 100V, 117V, 220V or 240V. 240V = = 2 20V = • — I I 17 V 10 • lo I00V 240 V when the power switch is turned on, and then by shorting the resistance at a relay contact and suppiying the input voltage directly to the transformer primary. A 130"C thermal fuse is contained within the transformer and protects it from unusual heating. lf the fuse is blown, it is necessary to replace the transformer itself. 2.2. = 240V— 81 j --H00V 220V— 117V 7V 1 2" 20 V— J l 0 0 —-\ UV 220V i r - II7V 240V=^! o ! 0 220 V— IJ '•—100V 1OOV Fig. 1.3 2. PRINCiPLE OF OPERATION 2.1. Power Block Pre-stage Refer to Fig. 2.2. As all the Output stage consists of emitter-followers, the voltage gain is 1. Therefore, the gain required for power amplifier and NFB is obtained at the pre-stage. Generally, an increase in the number of transistor stages of an amplifier circuit increases distortion and phase shift. In large current amplification as seen with a power amplifier, a certain extent of distortion cannot be avoided and should be limited through use of NFB. However, excessive NFB is likely to cause unstable amplification as a result of phase shift in the amplifier or differences in Soudspeaker impedance. This is one of the drawbacks inherent to an NFB amplifier. I!7V Power Supply Refer to Fig. 2.1. The power transformier used in the 620 is of a troidai type. Generally, a troidai transformer is attacked by large rush current when the power switch is turned on. For the 620, such rush current is reduced by suppiying input voltage to the primary of the transformer via a resistor (6.8f2, 10 watts) only during the time of approx. 20 msec The power amplifier used in the 620 employs 8 transistors, of which only two serve for voltage amplification and the remaining six are used to provide the former two with the best operating conditions. A gain of approx. 100dB is obtained through these two transistors to perform power amplification and NFB. The amplifier of this configuration assures stable NFB with !ow noise and Iow distortion and with little phase shift. Q001 and Q007 are for voltage amplification; Q002 and Q003 form a current mirror circuit (the same current at both collectors); Q005 and Q008 provide a constant-current source; Q006 is for impedance conversion (emitterfollower); Q004 and Q001 make up a differential amplifier circuit. Thus, stable NFB is applied through a circuitry using these transistors. C005 determines the high-band characteristic of the voltage amplifier to prevent NFB from becoming unstable because of unbalanced Performance. R016 is a resistor for NFB. 2.1 2.3. Power Block Output Stage In the Nakamichi 620, for making a bias voltage, Varistor used *in the conventional design of amplifier is replaced with transistor base-emitter so that the 620 design improves bias stabiIity (against temperature or current changes) with Iower distortion. Especially for a class B push-pull amplifier, distortion cannot be reduced unless the positive and negative signal amplifiers are well balanced. The amplifier in the 620, however, is best balanced thanks to the vertically and horizontally Symmetrie configuration as shown in Fig. 2.3. This cireuit allows distortion of only 0.1% at 1KHz 100 watts Output even without NFB. This degree of distortion is Iow enough to make the amplifier used as a high-fidel ity unit even if it is given no NFB. Fig. 2.4 shows that a change in current flowing across the diode varies the terminal voltage and that ED changes with signal current. These changes result in the generation of distortion. It is a matter of course that signal current flowing across the diode will produce distortion. See Fig. 2.3. Transistors Q009, Q011, Q010 and Q012 that generate bias voltage form an emitter-follower cireuit of class A Operation. Thus this cireuit does not induce distorted Signals. Unless corrected perfectly against temperatures, the bias voltage of power amplifiers in the class B amplifier will increase distortion at Iow temperature or become unstable at high temperature. !t may safely be said that temperature compensation of a transistor can be more properly and effectively carried out by the transistor of the same strueture than a diode. For an ordinary class B amplifier, crossover distortion is reduced by increasing idling current thus overlapping the operating ranges of the positive and negative transistors. The overlap portion acts as a class A amplifier. Generally, the degree of amplification decreases where a change takes place from class A to B and no linear curve is obtained as shown in Fig. 2.5 (A). However, if the cireuit shown in Fig. 2.3 is current-driven, a linear curve can be obtained at the point of change from class A to B as shown in Fig. 2.5 (B). 'UTP'JT Fig. 2.2 + Vcc OUTPUT INPUT O -Vcc Fig. 2.4 Class B Class A Class B Class A Class B Class B (B) (A) Fig. 2.5 INPUTO Fig. 2.3 Fig. 2.6 illustrates a simplified version of the circuit shown in Fig. 2.3. Since the direct-coupled two-stage emitter-foliowers can be regarded to be one emitter-follower having greater current amplification, the Q009-Q011, Q010-Q012, Q017-Q019, and Q018-Q020 will be designated respectively to be Q1, Q2, Q3 and Q4 as shown in Fig. 2.6. When id is applied with the input used as current-source, ii and i 2 are given as foliows because of the Q1 and Q2 input impedances: Input impedance of Q1 Input Impedance of Q2 Therefore; • _ 02(04f2 0 i ( 0 3 r i + r3) «2 «0 + + ßi (03 n ß2 (04 xi r4) r4) id r3J Fig. 2 . 6 Class B +T3) ßiißs n r3) + 02 (04 r 2 + r 4 ) = + + Vcc Class A Class •id ~>4 X2 = -ßo id 0 1 0 2 0 3 (04 r 2 + r 4 ) 0i(03ri 01020304 0i03(ri 3 ) id +r4) + {(r + 010204(03 r i + r 2 (n r3 — ßz ßA \6~- ßo id (V i i - O ) id +r3/03> Fig. 2.7 If 0 of the Q1-Q3 pair is equal to that of the Q 2 - Q 4 pair, then 0i03=j32ß4 (assumed as0o)The following equation will be obtained: ßp2 i (r 2 +r 4 /j3 4 ) + ( n + r3/<33) } ßo 1 ( n + r 3 / p 3 ) + (r 2 +rjß4) \ . '° - id ßo id As a result, the same gain is obtained over the entire ränge as shown In Fig. 2.7. Thus, the rate of current ampüfication in the idling current ränge (Class A) is quite the same as that in the ciass B amplifier. It must be noted, however, that the idling current is not included in the conditions for making the equation valid. In other words, a change in idling current will neither change the Iinearity of curves nor produce distortion. Q013 and Q014 form a constant-current source; D005 and D006 are for temperature compensation; D003 and D004 prevent reverse-biased voitage from being applied in abnormal State; Q015 and Q016 form a current limiter that prevents overloading on the power transistor. 2.4. Peak Power Indicator Fig. 2.8 and Fig. 2.9 show, respectively, the circuit diagram and time chart of the peak power indicator. This circuit Switches the peak power indicator of R-channel or L-channel to red or green depending upon the Output power. level. The LOW and HIGH power indicator threshoid selectors located on the rear panel of the 620 select 1/5/25 watts and 25/50/Max. watts power levels, respectively. The green iamp glows for output power levels of 1,5,25 watts (LOW) or more, while the red Iamp glows for output power leveis of 25, 50 or Max. watts (HIGH). (Ref. 8 ^ ioad. if a 1617 loudspeaker is to be used, divide the indicated power levels by two.) The green iamp remains off while the red lamp is on. if both switches are set for 25 watts, the peak power indicator lamps will glow red only at that power point The peak power indicating lamps are extremely fast in responding to transmit Signals. A 0.1 millisecond power pulse will' cause the peak indicator to light and stay " o n " for 0.3 second. AMP1 is a full-wave rectifier for input waveforms (nameiy output waveforms to the loudspeaker). AMP2 is a peak detector. Capacitor C151 and resistor R156 determine the time constant for holding the voltage of which peak has been detected. AMP3 and AMP4 form a comparator that compares the output voltage of AMP2 with reference voltage (corresponding to power ievel 1, 5, 25 or Max. watts). AMP3 and AMP4 are operational amp. ICs with open collector output. Output of these amplifiers is - 5 V if the AMP2 output voltage is Iower than the reference voltage. In this State, transistors Q151 and Q153 are cut off and the lamps are off. In AMP4, if the AMP2 output voltage exceeds the reference, the AMP4 output is opened and base current flows into Q153 via resistor R163. As a result, Q153 is on and the indicating lamp glows red. Then, the coilector of Q153 is dropped to —5V and no current flows to Q151 via R164. Thus Q151 is cut off and the green lamp goes out. AMP4 has hysteresis in its input/output characteristic. 0151, 0152, and Q153, Q154 make up a sort of monostable multivibrator. When 0151 is on and Q152 is therefore on, a positive differential pulse is applied to the Q151 base via capacitor C152. Thus Q151 is held " o n " for a certain time. Q153 and 0154 operate in the same manner as above. R157 (R165) is a resistor causing a lamp to be pre-biased. In AMP3, if the AMP2 output voltage exceeds the reference, the AMP3 output is opened and base current flows into Q151 via resistor R164. As a result, Q151 is on and the indicating lamp glows green. AMP 1 AMP 2 ov + 6V AMP 3 (L0W.5W) _5V + 6V AMP 4 (HIGHI50W) _5V + 6V Q-151 COLLECTOR GREEN _sv + 6V Q153 COLLECTOR _5V Fig. 2.9 infinf ?[|] ^"7 --5V Fig. 2.8 =-3.__5W 13K//390K F.! —25W—6.8K//55K -4 ^5 25\V 50 W 6.8K//56K 3.3K//1OK 3. REMOVAL PROCEDURES 3.1. Cabinet Ass'y Refer to Fig. 3.1 and remove F01 and F02. 3.2. Rear Panel Ass'y Remove cabinet ass'y (item 3.1). Refer to Fig. 3.2 and remove F01 and F02. F03 F02- 3.3. Lamp Remove rear panei ass'y (3.2). Refer to Fig. 3.3 and remove F01 and F02, then remove F03, F04and F05, F01 ÖT 3.4. Switch Remove rear panel ass'y (3.2). Refer to Fig. 3.4 and remove F01 and F02, then remove F03 and F04 (power sw.), and F05 and F06 (indicator sw. ass'y). / ,#» Ü 3.5. Power Block Ass'y Remove cabinet ass'y (3.1). Refer to Fig. 3.5 and remove F01 t h r o u g h F04. Fig. 3.3 -F01 F01- F06- FÖ1 Fig. 3.4 Fig. 3.1 F01 FO3 -FO1 Fig. 3.5 Fig. 3.2 3.6. Jack Remove rear pane! ass'y (3.2). Refer to Fig. 3.6 and remove F01 through F04 (2-pin jack) and F05 through F07 (push terminal). FOT 3.7. Indicator P.C.B. Ass'y Remove cabinet ass'y (3.1). Refer to Fig. 3.7 and remove F01 through F03. 3.8. Relay P.C.B. Ass'y and Cement Resistor Remove cabinet ass'y (3.1). Refer to Fig. 3.8 and remove F01 and F02 (cement resistor), and F03 through F05 (relay P.C.B, ass'y). 3.9. Diode and Output P.C.B. Ass'y Remove cabinet ass'y (3.1). Refer to Fig. 3.9 and remove F01 and F02 (diode), and F03 and F04 (output P.C.B, ass'y). F06 Fig. 3.8 — F03 F02 — FO4 F02 F01 F02 Fig. 3.9 Fig. 3.7 3.10. Transformer and Capacitor Remove cabinet ass'y(3.1). Refer to Fig. 3.10 and remove F01 through F06, F07 and F08 (transformier), F09 through F11 (capacitor) and F12 through F14 (capacitor). F02 Fig. 3.10 4. READJUSTMENT OF POWER BLOCK The 620 uses no semi-fixed parts to enhance reliability. As long as all parts meet the specification, the published characteristics can be obtained without readjustment. Generally, no readjustment is required if only defective parts are replaced at repair. Observe the following precautions when repairing defective parts: (2) (3) 4.1. Relocating a wiring can cause larger distortion, Do not relocate the wiring, (4) 4.2. Fully tighten or tetighten the screws on the chassis to decrease the resistance between GND terminals. 4.3. If a new semiconductor is installed in the power block, a perfect balance should be held between it and the existing semiconductors in the block. An imperfect balance can cause larger distortion or unwanted oscillation. To maintain a good baiance, connect an 812 100W load resistance to the output terminal, measure distortion and check that it meets the following requirements: (In this case, the residual distortion factor of the instrument shouid be Iower than the specified value.) (1) Output 1 watt, 1 and 10 KHz input Signals; less than 0.005% (2) Output 100 watts, 1 and 10 KHz input signais; less than 0.007% Described here are the possible causes for defects and the recommended remedial Steps: (1) The characteristic of one transistor does not match that of the other transistor when they are used as a pair. Usually, the idling current of power transistors Q019 and Q020 is approx. 20mA 30mA. If it is Iower, the distortion at 1 watt will increase. In such a case, solder additional 33K12 parallel to R018 and R019 (33Kft), respectively, from the dip side of the printed circuit board. Improper locations of power supply wiring will increase the distortion at 100 watts. If oscillation occurs, the distortion will become large at both 1 watt and 100 watts. Sometimes, oscillation cannot be observed even on a synchroscope if it invoives frequencies as high as several MHz. Osciilation may have occurred if the distortion is large though the external operating voltage remains normal. Try the following Steps to eliminate oscillation: (a) Add ceramic capacitors of the same capacity parallel to C010 and C011 (0.047^, 100V). (b) Increase C013 (100pF) (by adding a 47pF in parallel) or decrease the capacitance (by repiacing it with a 47p or removing it. If C013 is removed, make a short circuit by jumper wire.) (c) Short R017 (2712) or increase it to 4712. 2 L s--8 i 1 o x rjL* cofJ H „ I M f? H ff • i # ! f rvjwtn: öLUUr. vy " j Fig. 4. 10 5. MOUNTING DiAGRAM AND PARTS LIST Note: Mounting diagram shows a dip side view of the printed circuit board. 5.1. Power Block Ass'y 5.1.1. Power Block P.C.B. Ass'y 1 A R038 0.22 5W /l _ a 0 3 4 g ? < ? - 9 . . S R020 220 Ö-^ T° Ö ° 1 K " N ~ *0^™T^* O° ^ ... RO21 O 1 ? E RÜ4Q B RO39 0 22 5W . 6 Q O R ° 3 m JL "- 2SD555 Q014 4.7 2 2 O 8 E o^E^L^0^ i\i°^O??ZH^ - 33OOP HhO J^ RQ4H 0 O 2S733 K |\ 4.7 O ^ % ^ Q016 * / 1^ ^ 22 r \ l\ </ I R022 i |^ j 2SB6OO ? | Ö Sf 2 1 51K "RO35""'iK " ä 9 ^^2^7^ __ ... R024 51K ? 9 Q "O -fsT 2 6 ^^- 2 "^^^7 ? O £ <f Ä QOO9 2SB526 Fig. 5.1 Note: 1. Resistors R018, 019 and capacitor C013 2. Diode1S1555,transistors 2SB628and 2SD608 are the same as diode FDH-999, transistors 2SB536and 2SD381, respectively. ( * marks) are the parts for adjustment, and so typical value is shown. Refer to " 4 . Readjustment of Power Block". 5.1.2. Power Transistor P.C.B. Ass'y II I | I I B L I I I I I I i I !! ! pol f"ö"i Q011 2SB628 or2SB536 ! i l I \ ! C) ! O QO18 2SB628 ir2SB536 v \ \ II ( \ \ \ 0017 2SD608 or2SD38i 2SD555 Fig. 5.2 Output PX.B. Ass'y / -J ? i 31 - | - -L-OUT -L-INDICATOP BOARD R2O1 n.öft 2W -R-INDICATOR BOARD R-101 3.8Q 2W Fig. 5.3 11 ! ^j ^ a I I I I I I 4 \ I Q010 2SD608 r2SD38i 0019 0020 2SÜ60"cT 5,2. I 1 ( i ! \ I ; I I I I I I ! I l Q009 2SB628 -:,r2SB536 B ! I ^~~N I i 0012 2SD608 or2SD:81 Schematic Ref. No. Part No. Schematic Ref. No. Description JA03107A Power Block Ass'y BA03781A BA03780A 0E00231A 0E00026A Power Block P.C.B. Ass'y Power Transistor P.C.B. Ass'y Screw M2.6x8 Philips Pan Head FT (4 pcs.) Washer 2.6mm Spring (4 pcs.) BA03781A Power Block P.C.B. Ass'y 0B07676B 0B06078A Power Block P.C.B. Transistor 2SC1400 0B06074A Transistor 2SA750 (1) 0B06096A 0B06097A 0B06098A 0B06099A 0B06100A 0B06013A 0B06091A Transistor" '.Transistor.';;; Transistor Transistor . Transistor- Transistor-:::'-' Silicon Diode 2SB536 (K, L, M) 2SD381 (K, L, M) 2SB630 (Q, R, S) 2SD610 (Q, R, S) 2SC945A (K, P, Q) 2SA733 FDH-999 C007,014 015 C008 Part No. 0B05882A Ceramic Capacitor 0B05852A Electrolytic Capacitor 0B05883A 0B05892A 0E00566A Ceramic Capacitor 0.047M 100V M Ceramic Capacitor 100P 50V K Screw M3x6 Philips Pan Head (4 pcs.) Q016 0001,002 003,004 005,006 007,008 009,010 011,012 R001,009 R002 0B05878A R017 R018,019 R020,025 R021,024 R022, 026 030,031 R023, 027 R028,029 R032,037 R033, 034 035,036 R038,039 R040,041 R042 C001 0B05875A 0B05509A 0B01933A 0B05876A 0B05579A 0B01679A 0B05615A 0B05580A 0B01857A Carbon Carbon Carbon Carbon 0B05871A 0B05891A 0B05698A 0B05864A C002 C003 C004 C005 C006, 016 017 0B05893A 0B05880A 0B05798A 0B05806A 0B05881A Cement Resistor 0.22 5W Carbon Resistor 4.7 ERD-14 TJ Carbon Resistor 1.5K ERD-14 TJ Electrolytic Capacitor 47 M 16V M (MS) Ceramic Capacitor 680P 50V K Ceramic Capacitor 470P 50V !< Ceramic Capacitor 10P 50V K Ceramic Capacitor 22P 50V K Ceramic Capacitor 3300P 50V M Resistor 100 Resistor 22K Resistor 2.2 Resistor 1K ERO-25 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 CKG TJ TJ TJ TJ TJ ERD-14 ERD-14 ERD-14 ERD-14 TJ TJ TJ TJ L101,201 R101,201 R102, 202 C101,201 F101,201 ERO-25 CKG 12 .o. 1 1 — f\ 71 O 10V / A \ Nut Hex. M3 Washer 3mm (Fiber) BA03780A Power Transistor P.C.B. Ass'y 0B07677A 0B06094A 0B06095A 0B06096A 0B06097A 0B06083A 0B06081A 0E00731A 0E00732A Power Transistor P.C.B. Transistor 2SB536 (L) Transistor 2SD381 (L) Transistor 2SB536 (K, L, M) Transistor 2SD381 (K, L, M) Transistor 2SD555 Transistor 2SB600 Power Transistor Heat Sink (1 pce.) Power Transistor Bush (4 pcs.) Transistor Bush (6 pcs.) Spring Pin (4 pcs.) Screw M4x15 Philips Pan Head (4 pcs.) Washer 4mm Spring (4 pcs.) Nut Hex. M4 (4 pcs.) Washer 3mm Spring (6 pcs.) Nut Hex. M3 (6 pcs.) Screw M3x12 Philips Binding Head (6 pcs.) Washer 4mm (4 pcs.) Washer 3mm (12 pcs.) BA03777A Output P.C.B. Ass'y 0B07674B BA03784A 0B05872A 0B05870A 0B01602A 0B08239U 0J03510A 0E00166A 0E00606A Output P.C.B. Output Coil Ass'y 2.3MH Metai Oxide Resistor 6.8 2W Cement Resistor 6.8 10W Mylar Capacitor 0.33M 50V K Fuse 5A (2 pcs.) Output P.C.B. Holder (1 pce.) Screw M2x4 Cylinder Head (2 pcs.) Screw M3x6 Philips Pan Head (3A) (3 pcs.) 0E00720A 0E00721A 0E00723A 0E00718A 0E00741A TJ TJ TJ TJ TJ TJ TJ TJ TJ TJ JY 1 50V M UtUU/1oA 0J03505A 0J03488C 0J03493A 0J03494A 0J03560A 0E00719A R016 R003, 004 R005 R006 R007 R008,012 R010 R011 R013,014 R015 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 Q009 Q010 Q011,018 Q012, 017 Q019 Q020 Carbon Resistor 10K Carbon Resistor 1.8K Carbon Resistor 1.2K Carbon Resistor 82 Carbon Resistor 47K Carbon Resistor 27K Carbon Resistor 560 Carbon Resistor 39K Carbon Resistor 15K Carbon Resistor 56 Metal Film Resistor 360 Metal Film Resistor 10K Carbon Resistor 27 Carbon Resistor 33K Carbon Resistor 220 Carbon Resistor 51K Carbon Resistor 22 0B01888A 0B05614A 0B05623A 0B05631A 0B05641A 0B05743A 0B05575A 0B01854A 0B01683A 0B05890A 0B05877A 0.022M 1000M C010,011 C013 r\ ar\r\~) *i o A Q001,004 005 Q002,003 006 Q007 Q008 Q013 Q014 Q015 Description (4 pcs.) (2 pcs.) 5.3. Indicator P.C.B. Ass'y Note: Diode 1S1555 is the same as FDH-999 Fig. 5.4 5.4. Indicator Sw. P.C.B. Ass'y 5.5. ' oi | o | O o ! O | Indicator Lamp P.C.B. Ass y • ( 3 ) GRN I ? ü i Fig. 5.6 7 ? "0 iNDICATÜR BOARD) Fig. 5.5 13 5.6. Power Lamp P.C.B. Ass'y 5.7. Reiay P.C.B. Ass'y ORN AC3V. Fig. 5.7 Fig. 5.8 Schematic Ref. No. 10051,052 iC053 Q151, 153 251,253 Q152, 154 252, 254 DZ051 D051 D151, 152 251,252 D153, 154 155, 156 253, 254 255, 256 R051 R052 R053, 054 R151,154 161,251 254, 261 R152,252 R153, 164 253, 264 R155, 255 R156, 256 R157, 165 257,265 R158, 166 Schematic Ref. No. Description Part No. BA03776A Indicator P.C.B. Ass'y 0B07678C 0B06086A 0B06087A 0B06100A Indicator P.C.B. iC 1458 iC 3302 Transistor 2SC945A (K, F Q) 0B06013A Transistor 2SA733 0B06089A 0B06088A 0B06076A Silicon Diode Silicon Diode Silicon Diode XZ062 SIRBA 1S1553 0B06091A Silicon Diode FDH-999 0B05623A 0B05743A 0B05622A 0B01889A Carbon Carbon Carbon Carbon 0B05668A 0B01888A Carbon Resistor Carbon Resistor 0B01856A 0B05625A 0B05698A Carbon Resistor 8.2K ERD-14 TJ Carbon Resistor 220K ERD-14 TJ Carbon Resistor 1 5K ERD-14 TJ 0B05509A Carbon Resistor Resistor 1.2K Resistor 27K Resistor 2.2K Resistor 100K Description BA03779A Indicator Sw. P. C.B. Ass y 0B07679B 0B05641A 0B05776A 0B05560A 0B05676A 0B01682A 0B05508A 0B01681A 0B01888A 0B05629A 0B07105A 0B08237A 0J03501A 0E00166A indicator SW. P. C.ß. Carbon Resistor 47K Carbon Resistor 1M Carbon Resistor 18K Carbon Resistor 390K Carbon Resistor 6.8K Carbon Resistor 56K Carbon Resistor 3.3K Carbon Resistor 10K Carbon Resistor 2.7K Slide SW. 4P-H Connector Ass'y (1 pce.) Indicator SW. P. C.B. Holder (1 pce.) Screw M2x4 Cy linder Head (4 pcs.) BA03783A indicator Lamp P.C.B. Ass'y 0B07675A 0B08234U 0B08235A Lamp P.C.B. Lamp 12V 60mA (2 pcs.) 3P-H Connector Ass'y C (1 pce.) BA03782A Power Lamp P.C.B. Ass'y 0B07675A 0B08234U Lamp P.C.B' Lamp 0B08238A 3P-H Connector Ass'y D BA03778A Reiay P.C.B. Ass'y Q301 0B07673B 0B06074A Relay P.C.B. Transistor Q302 D301 D302 R301 0B06099A 0B06076A 0B06077A 0B05650A Transistor 2SD610 Silicon Diode 1S1553 Siiicon Diode 1S2358 Carbon Resistor 12K ERD-14 VJ R302 R303 R304 0B05561A 0B01920A 0B01921A Carbon Resistor 18K ERD14 VJ Carbon Resistor 100K ERD-14 VJ Carbon Resistor 330K ERD-14 VJ R305 R306 R307 0301 RL301 0B05565A 0B01879A 0B05563A 0B05586A 0B08228A Carbon Resistor 1.2K ERD-14 VJ Carbon Resistor 33K ERD-14 VJ Carbon Resistor 56K ERD-14 V J Mylar Capacitor 0.068M 50V K Relay HCI-TMCD 100VDC R055 R056 R057 R058 R059,061 R060, 062 R063 R064 R065 SW051,052 TJ TJ TJ TJ ERD-14 ERD-14 ERD-14 ERD-14 Part No. 82K ERD-14 TJ 10K ERD-14 TJ ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 ERD-14 TJ TJ TJ TJ TJ TJ TJ TJ TJ 12V 60mA (1 pce.) (1 pce.) 33K ERD-14 TJ oco 9fifi ZOO, ZDD R159, 160 167,168 259,260 0B01846A Carbon Resistor 4.7K ERD-14 TJ R162, 262 R163, 263 0B05776A 0B05771A Carbon Resistor Carbon Resistor C051 005 2 0151,251 0152, 252 0B01835A 0B01412A 0B05598A 0B05819A Electrolytic Capacitor 2200M Electrolytic Capacitor 10M Tantalum Capacitor 2.2M Electrolytic Capacitor 4.7M 0153,253 0B05861A Electrolytic Capacitor 6.8M 0B08185A 0B08236A 3P-T Post 4P-T Post 1 M ERD-14 TJ 12K ERD-14 TJ 18V 16V 25VM 16V n 11\ n o \ Ivi \IVIO/ 1 6V M (MS) (3 pcs.) (1 pce.) 14 2SA750 6. MECHANISM ASS'Y AND PARTS LIST 6.1. Synthesis (A01) -L01 -L02 L01 L02. p & L01 L02 01 (BOI) Fig. 6.1 Schematic Ref. No, Part No. AO1 Description Schematic Ref. No. Q'ty L01 L02 L03 L04 L05 0B05122A 0B05123A 0B05124A 0B05125A 0B05126A 0B05127A 0E00733A 0J03556A 0E00657A 0E00677A 0E00606A L06 L07 L08 L09 L10 0E00718A 0E00723A 0E00732A 0E00659A 0E00700A L11 0E00593A L12 L13 0E00197A 0E00037A Synthesis 01 02 L01 JA03103A HA03634A 0E00594A L02 1 1 5 0E00197A Mechanism Ass'y Cabinet Ass'y Screw M3x8 Philips Binding head (Bronze) Washer 3mm (Bronze) 301 JA03103A Mechanism Ass'y 1 01 02 03 04 05 06 07 08 09 10 11 0H03454A HA03658A 0H03456B 0M03683B BA03776A JA03104A JA03106A JA03105A JA03108A JA03107A 0J03506A Handle (B) Front Panel Ass'y Light-intersepting Shade Rear Name Plate Indicator P.C.B. Ass'y Main Chassis Ass'y Indicator Lamp Ass'y Power Lamp Ass'y Rear Panel Ass'y Power Block Ass'y Rear Angle Cord with Terminal A 2 1 0B05121A 5 2 1 1 1 2 1 1 2 1 1 15 Description Part No. Cord Cord Cord Cord Cord Cord with with with with with with Terminal Terminal Terminal Terminal Terminal Terminal B C D E F G M4x12Bolt(Hex.Socket Head) Washer 4mm (Black) Screw M3x5 Philips Pan Head Washer 3mm (Black) Screw M3x6 Philips Pan Head (3A) Nut Hex. M3 Washer 3mm Spring Washer 3mm Screw M3x10 Philips Pan Head Screw M5x16 Philips Pan Head (2A) Screw M3x6 Philips Binding Head Washer 3mm (Bronze) Earth Lug B-5 Q'ty 1 1 1 1 1 1 6 5 3 3 6 5 5 5 5 4 4 4 2 6.2. Mechanism Ass'y (B01) 01 01 L01 L02 L01 Fig. 6.2 16 6.3. Cabinet Ass'y (B02) 01 L01 Fig. 8.3 Schematic Ref. No. Part Mo. 802 HA03634A Cabinet Ass'y 1 01 02 03 0A03254A 0A00518C 0M03339A 0M03674A 0E00552A 0E00701A 1 4 1 1 4 4 0E00253A 0M03619A Cabinet Gum Foot Caution Labe! Shield Foil 610 Nut Hex. M3 Screw M3x'10 Philips Binding Head (Bronze) Washer 3.3mm Gate Bind Plate JA03104A Main Chassis Ass'y 1 JA03109A 0B07092U BA03779A 0J03469A BA03777A 0B06085A 0B05874A BA03778A 0B05873B Main Chassis Sub Ass'y Power SW. Indicator SW. P.C.3, Ass'y SW. Shade Output P.C.B. Ass'y Silicon Diode S15VB-20 Cement Resistor 6.8P- 10W Relay P.C.B. Ass'y Electrolytic Capacitor 39,000,uF 63V 1 I 2 1 1 1 1 2 L01 L02 LOS C01 01 02 03 04 05 06 07 08 09 Description Schematic Ref. No. Q'ty 4 1 Part No. 10 11 0B06554U 0J03508B L01 0E00533A L02 0E00007A L03 L04 0E00219A 0E00606A L05 L06 L07 0E00037A 0J03512A 0E00667A LOS L09 L10 L11 0J03511A 0E00709A 0E00513A 0E00727A L12 0E00726A L13 0E00142A Description Power Transformer Earth Angle Screw M3x5 Philips Countersunk Screw M2.6x5 Philips Countersunk Screw M2.6x5 Philips Pan Head Screw M3x6 Philips Pan Head (3A) Earth Lug 8-5 Capacitor Holder Washer Screw M4x6 Philips Pan Head (2A) Transformer Holder Washer Washer 5mm Spring Nut Hex. M5 Screw M4x8 Philips Pan Head (2A) Screw M4x1 5 Philips Pan Head (3A) Washer 2.6mm Q'ty 1 1 2 1 2 5 1 4 4 4 4 4 2 1 2 i 17 6.4. Main Chassis Ass'y (C01) L11 LQ7 9 L06 03 Fig. 6.4 18 6.5. Front Panel Ass'y (C02) L01- 01 Fig. 6.5 6.6. Rear Panel Ass'y (C03) ,13 L04L03 06 L05 01 LÖ2 Fig. 6.6 19 6.7. Indicator Lamp Ass'y (C04) 6.8. Power Lamp Ass'y (C05) L01- Fig. 6.7 Schematic Ref. No. Part No, C02 HA03658A Front Panei Ass'y 01 02 03 L01 0H03452B 0H03453C 0J03559B 0E00740A Front Panel Indicator Base Lamp House Holder Spring (B) Screw M2x8 Cylinder Head C03 JA03108A Rear Panel Ass'y 01 02 03 04 05 JA03110A 0B03072A 0J03502A 0B08233U 0H03335A 06 07 08 08 09 10 11 12 0H03334B 0B08231U 0B08230U 0B08232U 0B08037U 0B03900U 0A03154B 0H03366A 13 14 L01 0B08240U 0B03877U 0E00594A L02 L03 L04 L05 0E00157A 0E00172A 0E00507A 0E00590A L06 0E00591A L07 0E00037A Q'ty Schematic Ref. No. Part No. 1 C04 JA03106A Indicator Lamp Ass'y 2 1 3 3 12 0J03509A JA03111A 0J03489A 0J03507C BA03783A 0E00724A Filter Stopper Filter Ass'y Lamp House Light-Intercepting Plate Indicator Lamp P.C.B. Ass'y Screw M2.6x5 Philips Pan Head (Tapping) 1 1 01 02 03 04 05 L01 1 1 1 1 2 Rear Panel Sun A^s'v 2P Pin Jack Push Terminal Holder Push Terminal Voltage Seiector Cover SO 1 1 1 C05 JA03105A Power Lamp Ass'y 1 Acrylic Cover Fuse Socket Fuse 3.1 5A (220, 240V) Fuse 5A (100, 117V) Cord Bush (C) Power Cord Cord Spacer Washer for/Voltage Seiector Cover Spark Killer Voltage Seiector Socket Screw M3x8 Philips Pan Head (Bronze) Washer 3mm (Black) Washer 3mm Toothed Lock Nut Hex. M3 Screw M3x12 Philips Pan Head (Bronze) Screw M3x20 Philips Pan Head (Bronze) Earth Lug B-5 1 1 1 1 1 1 01 02 03 04 L01 0J03509A 0J03490A 0J03489A BA03782A 0E00724A Filter Stopper Orange Filter Lamp House Power Lamp P.C.B. Ass'y Screw M2.6x5 Philips Pan Head (Tapping) 1 1 1 1 2 Description 1 1 1 2 1 1 4 6 4 4 2 2 1 20 Description Q'ty 2 D 8. PERFORMANCE DATA Output vs Total Harmonie Distortion : 1kHz Load Imp. Filter: : s i i | 1 1 1j I 1 — i Frequency vs Total Harmonie Distortion Output: 100 Watts Constant Load Imp: 8 ohms 8 ohms 400Hz H.P. SOkHz L.P. 4 T 2 0 1 0.1 6 b 1 1 | l . j i | - - — i i Ltl i 0.01 6 ! 0.001 t HJ 4 , 7 J 0.1 ,,2 4 4 6 10 2 4 6 100 I y 2 2 0.001 4 6 4 6 100 2 4 Output Power (Watts 6 1k 2 4 6 !0k 2 4 Frequency (Hz) Output vs Harmonie Distortion Frequency: 1kHz Load Imp: 8 ohms Output Power vs IM Distortion 60Hz : 7kHz ( 4 : 1 ) !! 4 11 ! I 2 I 0.001 0.1 6 4 I 6 4 .i - ^ To al —. 2 , 00001 6 4 2 ^ > 0.01 6 4 4; 7th •— u I i I 2 4 6 l 2 4 6 10 2 \ \ --- Output Power (Watts; j— r ]^ The distortion -Jata immediately above was obtained with rhe aid of a Bruel Pi Kja^r 3348 R^al Time Anaiyzer. These measuniments cannot b<i rnade with -.onvintional distortion analyzers because of noise focto.-:. 10 2 4 6 10 2 4 -< i00 Output Power 'Wal Fig. 8 22 ;| "Ar 0.001 4 6 100 4 .4- :: — 2 4 V 9. BLOCK DIAGRAM +53V INPUT OUTPUT 1V/10K 1OOW AC 8fl INPUT •4-6V -5V (To Power Peak Indicator Circuit) -f6V GREEN RED Fig. 9 23 10. SCHEMATIC DIAGRAM I VTTL.I\ ULUV/fN I 0002 g f 1 POWER BLOCK a 0003 T}HB fo ' Note: 1. i k016 W' | shows the reference circuit voltage 2. In the power block circuit, resistor R018,019 and capacitor C013 ( * marks) are the parts at approx. 30 watts Output. for adjustment, and so typical value is shown. 24 11. SPECIFICATIONS Power Source Power Consumption Power Output IHF Power Bandwidth (both Channels driven) Damping Factor Total Harmonie Distortion Intermodulation Distortion Frequency Response !nput Impedance Residual Noise Level Signal-to-Noise Ratio Crosstalk Peak Power Indicators Dimensions Weight • , 100/117/220/240 V AC, 50/60 Hz 50 VA at idling 700 VA with both Channels driven to clipping into 8 ohm loads 100 Watts per Channel minimum continuous sine wave ("RMS") at 8 ohms, 5-20,000 Hz with less than 0.01 %THD 50 Watts per Channel at 16 ohms 5 - 50,000 Hz for less than 0.1%THD 5 - 20,000 Hz for less than 0.01%THD 5 - 10,000 Hz for less than 0.005%THD Greater than 100 (1 KHz, 8 ohms) Less than 0.002% @ 1 KHz or below Less than 0.005% @ 10 KHz or below Less than 0.002% (60 Hz: 7 KHz, 4:1, 8 ohm load, 100 W Output) 5 - 100,000 Hz +0, -1 dB 10 K ohms Less than 0.05 mV (IHF A Network) Less than 0.1 mV (linear) Better than 120 dB at rated Output (IHF A, input shorted) Better than -70 dB @ 1 KHz Green at 1 W, 5 W, 25 W, seiectable Red at 25 W, 50 W, Maximum (110-130 W) selectabie (Response time: responds to 0.1 ms pulse — off after 0.3 sec) 15.75"(W) x 7.44"(H) x 9.76"(D) 400mm (W) x 189mm (H) x 248mm (D) 27.6 Ibs. (12.5 kg) Specifications and appearance design are subject to change for further improvement without notice. 26 Service Manual Nakamichi 620 NAKAMICHI RESEARCH INC. 1-153 Suzukicho, Kodaira, Tokyo Phone: (0423) 42-1111 Telex: 2832610 (NAKREI J) Cable: NAKAMICHI KOKUBUNJI NAKAMICHI RESEARCH (U.S.A.) 3NC. West Coast Office 1101 Colorado Avenue, Santa Monica, Caiif. 90401 Phone: (213) 451-5901 Telex: 652429 (NAKREi SNM) NAKAMICHI RESEARCH (U.S.A.) INC. New York Office 220 Westbury Avenue, Carle Place, N.Y. 11514 Phone: (516) 333-5440 Telex: 144513 (NAKRE! CAPL) Service Information Model Seria! N a Nakamichi 620 (Power Amplifier) from 4104902 Subject Addition of Protector Circuit NAKAMICHI [\j 0 ; I. D a t e OOD-M-0044 ( 1 / 5 ) l September, 1977 General: A. Purpose: A protector circuit has been added to prevent Speakers from breakage, as the breakage of transistors in 620 would induce possible breakage of the Speaker. Note; When the protector circuit is activated (speaker terminals shorted with relay contacts), the power supply for 620 is required to be once switched off so as to release the protecting function. The power should again be supplied for at least 5 minutes after switching off, B. Modification: Additional Parts: Part No. BA03865A Protector P.C.B. Ass'y .... 1 pce, 0J03687A E.P. Stud A ,...2 pcs. 0E00030A Washer 3mm . ,.. 1 pce. Modified Parts: Main Chassis Ass T y . ... Part No. has been changed from JA03104A to JA03104B (including Protector P.C.B, Ass ? y). Mechanism Ass 7 y ..,,,,, Part No, has been changed from JA03103A to JA03103B (including Protector P.C.B, Ass'y), C. Principle of Operation: The protector circuit aims at protecting the Speaker with a shortcut from the Speaker terminals to GND by operating the relay in Protector P.CB. Ass ! y when D.C, voltage is impressed between Speaker terminals against any possible accident. The time length required for protector to operate are specified as below according to D.C. voltages (either plus or minus) impressed between the Speaker terminals: D.C. Voltage betx^een Speaker Terminals Time required till Protector operates 50V DC approx, 0.5 sec or less 20V DC approx. 1.2 sec ± 30% OOD-M-0044 (2/5) D.C. Voltage between Speaker Terminals Time required till Protector operates 10V DC approx, 2,5 sec ± 30% 5V DC approx. 4 ^ 10 sec Once the protector circuit is activated, the protecting State is retained until the power supply to 620 is disconnected to release it. The power should be supplied after power capacitors are fully discharged (for approximately 5 minutes or more). Note: The protector circuit in 620 may occasionally be activated if a high transient D,C. voltage is delivered from the preamplifier connected with 620 at the time when the power supply for the preamplifier is turned on. The cause is not from any trouble in 620, For its countermeasure? the power for 620 is recommended to be supplied last of all. H . Parts List: Part No, BA03865A 0J03687A E.P. Stud A ,.,.2 pcs. 0E00030A Washer 3mm . .,, 1 pce, Schematic Part No. Ref, No. O4013402 403 0404 D401?402 D403 ZD401 ZD402 R401,402 R403;;404 407 R405.406 R408' R409,410 R4U ,414 R412 R413,415 C401.402 C403 RY401 Protector P.C.B. Ass'y .,,,1 pce, Description BA03865A Protector P.C*B. Ass'y 0B07727A 0B06078A Protector P.C.B, Transistor 2SC1400 0B06074A 0B01909A 0B06109A 0B06073A 0B06002A 0B01921A 0B05650A Transistor 2SA750 Silicon Diode 1S1555 Silicon Diode GP08B Zener Diode 10S Zener Diode 15R Carbon Resistor 330K ERD-25V J Carbon Resistor 12K ERD-25V J 0B01781A 0B05593A 0B01920A 0B05607A 0B01795A 0B01833A 0B05885A 0B01290A 0B07171A 1K ERD-25V J Carbon Resistor Carbon Resistor 150K ERD-25V J Carbon Resistor 10OK ERD-25V J Carbon Resistor 180 ERD-25V J Carbon Resistor 4,7K ERD-25V J Carbon Resistor 10K ERD-25V J Electrolytic Capacitor 100yF 10V Ceramic Capacitor 0,01yF 50V Relay HB-2T OOD-M-0044 (3/5) HI. Mounting Diagram and Schematic Diagram: Refer to Figs. 2 and 3. ~N . Modification Procedures for the Current Models: Following shox>zs the way hox^ to assemble the Protector P.C.B. Ass T y in the current Models. A. Parts to be required: Part No. BA03865A Protector P.C.B. Ass T y 1 pce. 0J03687A E.P. Stud A .,.,2 pcs. 0E00030A Washer 3mm .... 1 pce. B. Modification Procedures: Refer to Fig. 1. 1. Disassemble the Cabinet by removing five screws. . 2, Remove two screws from the Relay P.C.B. Ass 7 y and replace with E.P. Studs. Note to add a washer as shown in the figure, 3, Loosen the screw which fixes the cement resistor 6.8fi 10W to the chassis, then move the cement resistor to prevent contacting the Protector P.C.B. Ass 7 y. 4, Assemble the Protector P.C.B. Ass'y. 5, Disassemble the Rear Angle by removing two screws, 6, Solder the Signal wires (WHT,WHT) of the Protector P.C.B. Ass T y to the Speaker terminal (output terminal) plus side of both Channels, 7, Solder the RED wire of the Protector P.C.B, Ass T y to the plus terminal (RED wires are already soldered) of the capacitor Cl 39?000yF 63V, 8, Solder the BLU wire of the Protector P.C.B» Ass 7 y to the minus terminal (BLU wires are aiready soldered) of the capacitor C2 39,000yF 63V. 9, Bind these wires at an appropriate point, 10, Assembie the Rear Angle, 11, Assemble the Cabinet, OOD-M-0044 Protector P.C.B.Assy Washer 3mm Cement Resistor Reiay P.C.B.Assy Fig. 1 Protector P.C.B. Ass'y Mounting Diagram (4/5) Schematic Diagram J + 53V LEFT{^7- lNPUT,-t-, RIGHTVM POWER BLOCK rrr-\\- ' ^ ^ ^ E12 i r'L3OI H<:\ -TMDC 100 >n I _J I RELAY 30ARD iR^ 3 OOD-M-0044 ( 5 / 5 ) ' | RI---IW R2---5W R3---25W R4---25W R5---50W R6---MAX 47K//1M I8K//39OK 6.8K//5-.K 6.8K//56K 3.3K//IOK 2.7K LAMP P C B. "1 OUTPUT TERMINAL L =PDI Q r INDICATOR SW. PC.B. I 1 LAMP PC.B. 30ARD u I Ri.-.tw R2--5W R3 ---2bW R4---25W R5---5OW R6---MAX H 4 3 2 —GuuuD— BOARD Fig. 10 -7K//1M I8K//39OK 6.8K//56K 6.8K//56K 3.3K//IOK 2.7K I