Nakamichi 620, Service Manual

Page 1: ...Nakamichi Service Manual Nakamichi 620 power amplifier...

Page 2: ...ting Diagram and Parts List 11 5 1 Power Block Ass y 11 5 1 1 Power Block P C B Ass y 11 5 1 2 Power Transistor P C B Ass y 11 5 2 Output P C B Ass y 11 5 3 indicator P C B Ass y 13 5 4 Indicator Sw P...

Page 3: ...er 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...

Page 4: ...es of an ampli fier 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 th...

Page 5: ...ode 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...

Page 6: ...3 0 3 id If 0 of the Q1 Q3 pair is equal to that of the Q2 Q4 pair then 0i03 j32 4 assumed as0o The following equation will be obtained Class B Class A Class o id z A 6 o id V ii O Fig 2 7 p2 i r2 r4...

Page 7: ...that compares the output voltage of AMP2 with reference voltage corre sponding to power ievel 1 5 25 or Max watts AMP3 and AMP4 are operational amp ICs with open collector output Output of these ampl...

Page 8: ...ass y 3 2 Refer to Fig 3 3 and remove F01 and F02 then remove F03 F04and F05 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...

Page 9: ...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 Dio...

Page 10: ...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 capa citor F02 Fig 3 10...

Page 11: ...ig nais 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 th...

Page 12: ...1 Resistors R018 019 and capacitor C013 marks are the parts for adjustment and so typical value is shown Refer to 4 Read justment of Power Block 2 Diode1S1555 transistors 2SB628and 2SD608 are the sam...

Page 13: ...4 TJ Carbon Resistor 22 ERD 14 TJ Carbon Resistor 100 ERD 14 TJ Carbon Resistor 22K ERD 14 TJ Carbon Resistor 2 2 ERD 14 TJ Carbon Resistor 1K ERD 14 TJ Cement Resistor 0 22 5W Carbon Resistor 4 7 ERD...

Page 14: ...5 3 Indicator P C B Ass y Note Diode 1S1555 is the same as FDH 999 5 4 Indicator Sw P C B Ass y o i o o O O I i 7 0 iNDICAT R BOARD Fig 5 4 5 5 Indicator Lamp P C B Ass y 3 GRN Fig 5 6 Fig 5 5 13...

Page 15: ...J TJ TJ 18V 16V 25VM 16V n 11 n o Ivi I V I O Electrolytic Capacitor 6 8M 1 6V M MS 3P T Post 3 4P T Post 1 pcs pce Schematic Ref No R055 R056 R057 R058 R059 061 R060 062 R063 R064 R065 SW051 052 Q301...

Page 16: ...ss y Power Block Ass y Rear Angle Cord with Terminal A Q ty 1 1 5 5 1 2 1 2 1 1 1 2 1 1 2 1 1 Schematic Ref No L01 L02 L03 L04 L05 L06 L07 L08 L09 L10 L11 L12 L13 Part No 0B05122A 0B05123A 0B05124A 0B...

Page 17: ...6 2 Mechanism Ass y B01 01 01 L01 L02 L01 Fig 6 2 16...

Page 18: ...e S15VB 20 Cement Resistor 6 8P 10W Relay P C B Ass y Electrolytic Capacitor 39 000 uF 63V Q ty 1 1 4 1 1 4 4 4 1 1 1 I 2 1 1 1 1 2 Schematic Ref No 10 11 L01 L02 L03 L04 L05 L06 L07 LOS L09 L10 L11 L...

Page 19: ...6 4 Main Chassis Ass y C01 L11 LQ7 9 L06 03 Fig 6 4 18...

Page 20: ...6 5 Front Panel Ass y C02 L01 01 6 6 Rear Panel Ass y C03 Fig 6 5 L04L03 13 06 L05 01 L 2 Fig 6 6 19...

Page 21: ...et 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 W...

Page 22: ...2 D...

Page 23: ...0 2 4 6 1k 2 4 6 0k 2 4 Frequency Hz Output vs Harmonie Distortion Frequency 1kHz Load Imp 8 ohms 4 2 0 001 6 4 2 00001 6 4 I I I u 11 To 4 7th al i 2 4 6 l 2 4 6 10 2 4 6 100 Output Power Watts The d...

Page 24: ...V 9 BLOCK DIAGRAM 53V INPUT 1 V 1 0 K AC INPUT OUTPUT 1OOW 8 f l 4 6V To Power Peak 5V Indicator Circuit f6V GREEN RED Fig 9 23...

Page 25: ...gf 0003 a T HB fo 1 POWER BLOCK k016 W Note 1 i shows the reference circuit voltage at approx 30 watts Output 2 In the power block circuit resistor R018 019 and capacitor C013 marks are the parts for...

Page 26: ...02 1 KHz or below Less than 0 005 10 KHz or below Intermodulation Distortion Less than 0 002 60 Hz 7 KHz 4 1 8 ohm load 100 W Output Frequency Response 5 100 000 Hz 0 1 dB nput Impedance 10 K ohms Res...

Page 27: ...832610 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...

Page 28: ...3865A Protector P C B Ass y 1 pce 0J03687A E P Stud A 2 pcs 0E00030A Washer 3mm 1 pce Modified Parts Main Chassis AssT y Part No has been changed from JA03104A to JA03104B including Protector P C B As...

Page 29: ...all H Parts List Part No BA03865A Protector P C B Ass y 1 pce 0J03687A E P Stud A 2 pcs 0E00030A Washer 3mm 1 pce Schematic Ref No Part No Description O4013402 403 0404 D401 402 D403 ZD401 ZD402 R401...

Page 30: ...re 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 Ass7 y 4 Assemble the Protector P C B Ass y 5 Dis...

Page 31: ...OOD M 0044 4 5 Washer 3mm Cement Resistor Protector P C B Assy Reiay P C B Assy Fig 1 Protector P C B Ass y Mounting Diagram...

Page 32: ...Schematic Diagram LEFT 7 lNPUT t RIGHTVM J 53V POWER BLOCK rrr I _ J E12 n r L3OI i H TMDC 100 I RELAY 30ARD iR 3...

Page 33: ...OOD M 0044 5 5 RI IW 47K 1M R2 5W I8K 39OK R3 25W 6 8K 5 K R4 25W 6 8K 56K R5 50W 3 3K IOK R6 MAX 2 7K...

Page 34: ...1 OUTPUT TERMINAL 30ARD L r Q INDICATOR SW PC B u Ri tw 7K 1M R2 5W I8K 39OK R3 2bW 6 8K 56K R4 25W 6 8K 56K R5 5OW 3 3K IOK R6 MAX 2 7K H 4 3 2 GuuuD LAMP P C B PDI I 1 LAMP PC B I I BOARD Fig 10...