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Bose 550 Service Manual

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Model 550
AM/FM Stereo Receiver
Service Manual
Part Number 112429 REV 01

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Summary of Contents for Bose 550

  • Page 1 ® ® Model 550 AM/FM Stereo Receiver Service Manual Part Number 112429 REV 01...
  • Page 2 Contents Safety Information ..........................3 Electrostatic Discharge Sensitive (ESDS) Device Handling ............4 Specifications ..........................5-6 Technical Description ........................7 Disassembly/Assembly Procedures ..................8-10 Figure 1. Antenna Placement Diagram ..................10 Test Procedures ........................11-14 Figure 2. AM/FM Adjustment Location ................... 12 Figure 3.
  • Page 3 SAFETY INFORMATION 1. Parts that have special safety characteristics are identified by the symbol on schematics or by special notes on the parts list. Use only replacement parts that have critical characteristics recommended by the manufacturer. 2. Make leakage current or resistance measurements to determine that exposed parts are acceptably insulated from the supply circuit before returning the unit to the customer.
  • Page 4 CAUTION: THE 550 RECEIVER CONTAINS NO USER-SERVICEABLE PARTS. TO PRE- VENT WARRANTY INFRACTIONS, REFER SERVICING TO WARRANTY SERVICE STA- TIONS OR FACTORY SERVICE.
  • Page 5 SPECIFICATIONS AM Tuner: 20 dB Usable Sensitivity 350 uV (ferrite loopstick) Adjacent Channel Selectivity 35 dB Total Distortion .9% (400 Hz @ 30% Modulation) Image Rejection 37 dB IF Rejection 45 dB Signal to Noise Ratio 40 dB FM Tuner: IHF Usable Sensitivity 2.0 uV/11.25 dBf (Mono) 3.5 uV/16.11 dBf (Stereo)
  • Page 6 SPECIFICATIONS Input Sensitivity Impedance: Aux. and Tape 150 mV/ 50k Ohm Capacitance: Phono 2.75 mV/ 47k Ohm, 150 pF Source and Room Low Filter -3 dB @ 100Hz Compensation -7 dB max. @ 20Hz Controls: Low Frequency Control ±8 dB @ 140Hz Narrow Position (center frequency) ±1 dB @ 20Hz and 1kHz...
  • Page 7 Bose 901 loudspeakers. The built-in equalizer can be switched into the circuit when playing Bose 901 Series III or Series IV speak- ers. You can pre-set the Model 550 via the rear panel switches for various combinations of loudspeakers.
  • Page 8 DISASSEMBLY/ASSEMBLY PROCEDURES Note: Numbers in parentheses corre- 6. Front Panel Replacement spond to the callouts in Figure 8. 6.1 Place the front panel onto the unit and 1. Top Cover Removal clip the bottom of the front panel into place. 1.1 Remove the 4 screws (A-14) located 6.2 Secure the top of the front panel and on each side of the unit.
  • Page 9 DISASSEMBLY/ASSEMBLY PROCEDURES 15.4 Replace any defective bulbs. 11. Dial Lamp Assembly Removal 16. Meter Lamp Assembly Replacement 11.1 Perform procedure 1. 16.1 Place the PC board into the housing 11.2 Carefully slide the dial lamp PC board and secure it to the housing. to the left (with the unit facing you) and lift the board off of the clips.
  • Page 10 TEST PROCEDURES 2. FM/MPX Tuner Adjustment 1. AM Tuner Adjustment Procedure Note: Refer to the antenna placement 2.1 Connect an FM signal generator to the diagram Figure 1. antenna terminals on the rear panel. 1.1 Connect an AM signal generator to an 2.2 Connect a voltmeter to the tape output AM loop antenna.
  • Page 11 TEST PROCEDURES FM Alignment Procedure MPX Alignment Procedure...
  • Page 12 Figure 2. AM/FM Adjustment Location...
  • Page 13 TEST PROCEDURES 3. Loudness Control Procedure 5.3 Reference a dB meter to the output with the low frequency control centered and Note: Use the following control settings. the wide/narrow switch in the OUT position. Slide pots centered, speaker A switch selected with the output connected to an 8 5.4 Slide the control from one side to the ohm load, all switches out except for the...
  • Page 14 TEST PROCEDURES 8. Amplifier Adjustment Procedure 7.3 Reference a dB meter to the output. Note: Preheat the unit for about 20 minutes 7.4 Check the response using the chart prior to performing the following procedure. below. 8.1 Connect a DC voltmeter to the test points TP 501-502 (across R536) for the ®...
  • Page 15 Figure 4. Block Diagram...
  • Page 16 Figure 5. Wiring Diagram...
  • Page 17 Figure 6. Main PCB Layout...
  • Page 18 Figure 7. PCB Layout...
  • Page 19 Figure 8. Exploded View...
  • Page 20 Figure 9. Dial String Diagram...
  • Page 21 Figure 10. Pinout Location Diagram...
  • Page 22 PART LIST NOTES 1. This part is not normally available from Customer Service. Approval from the Field Service Manager is required before ordering. 2. The individual parts located on the PCBs are listed in the Electrical Parts Lists. This part is critical for safety purposes. Failure to use a substitute replacement with the same safety characteristics as the recommended replacement part might create shock, fire and/or other hazards.
  • Page 23 PART LIST Main Assembly (see Figure 8) Item Description Part Note Number Number Front Panel Assembly 112889 Cabinet 112344 Bottom Plate 112890 Dial Window 112345 Control Panel 112346 Pointer 112347 Terminal Chassis 112891 Dial Scale 112892 Tuning Knob 112277 A-10 Push Knob 112228 A-11...
  • Page 24 PART LIST Main Assembly (see Figure 8) Item Description Part Note Number Number B-20 Drum 112912 B-21 Drum Spring 112913 B-22 Shaft Washer 109842 B-30 Sub. Chassis (B) 112914 B-32 Shield Paper (B) 112915 B-33 Pulley Stud (A) 112916 B-34 Ground Lug 112357 B-35...
  • Page 25 112330 VR453-456 25K (bass and treble) 112310 Resistors Reference Description Part Note Designator Number R1, 37, 549,550 1mΩ (J) carbon 113282 R2,7,12,17,58,71 22Ω (J) carbon 113284 220Ω (J) carbon 113349 R4, 13, 49, 51, 63, 64 3.3kΩ (J) carbon 107157-...
  • Page 26 PART LIST Resistors Reference Description Part Note Designator Number 220kΩ (J) carbon 113318 16kΩ (J) carbon 114089 4.7Ω (J) carbon 114090 R57, 79, 80, 93, 479, 100kΩ (J) carbon 113281 480, 497, 498, R59, 60, 67, 68 2.7kΩ (J) carbon 113340 R65, 66 820Ω...
  • Page 27 Resistors Reference Description Part Note Designator Number R559, 560 330Ω 1w (J) metal oxide 112321 R561 47Ω 1/2w (J) carbon 113251 R563, 564 82Ω 2w (J) metal oxide 112322 R565 18Ω (J) carbon 114122 R566-570 220Ω (J) carbon 113256 R571 27kΩ...
  • Page 28 PART LIST Capacitors Reference Description Part Note Designator Number 470P (J) Polyster 109945 .047 (M) Polyster 112222 .47/25V (LL) Electrolytic 114079 C63, 64 .22/25V (LL) Electrolytic 114080 C65-68 .0056 (YB) Ceramic 100397-7 C69, 70 .001 (YB) Ceramic 100397-3 C71, 72, 75, 76, 87, 88, 4.7/35V (LL) Electrolytic 114081 95, 96, 477, 478...
  • Page 29 113407 C537 1000/35V Electrolytic 114115 C538 220/50V Electrolytic 114116 C539, 540 6800/50V Electrolytic 114117 C543, 544 1000/16V Electrolytic 113364 C549, 550 47/50V Electrolytic 114118 C601 .0068 112363 C902, 904 .0018 (J) Polyster 109967 C903 .0036 (J) Polyster 114126 C905 1/25V Electrolytic...
  • Page 30 PART LIST Integrated Circuits Reference Description Part Note Designator Number HA11211 (FM IF) 112114 HA1156W (MPX) 112294 IC3, 4 BA312 (PRE AMP) 112295 IC451 FS78 15C (ZENER IC) 112290 IC452 4558D (OP AMP) 110369 Diodes Reference Description Part Note Designator Number D1, 5 1S2787...
  • Page 31 VOLTAGE CONVERSION INSTRUCTIONS Refer to Figures 11 and 12 for the following procedures 120 to 240 Voltage Conversion 1. Locate the brown and yellow power transformer wires, remove the crimp insulator, and separate the wires. 2. Tape or insulate the brown wire (this wire is not used for 240 volt wiring, but it will be needed to convert back to 120 volt wiring).

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