BOSE 300 PM Schematic

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MODEL 300PM LOUDSPEAKER

1997 Bose Corporation

Service Manual

Part Number 193626 Rev. 00

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CONTENTS

Note: This service manual has been updated with information from supplement 193626-S2, affecting part numbers for PTC1 and PTC2.

Specifications......................................................................................................................3

SmartProtect Crossover PCB operation and troubleshooting ....................................... 4

Disassembly/Assembly procedures...............................................................................5-6

Test procedures .................................................................................................................. 7

Figure 1. Model 300PM Loudspeaker test setup diagram .............................................................. 7

Figure 2. Model 300PM Loudspeaker driver wiring diagram........................................................... 8

Figure 3. Model 300PM Loudspeaker schematic diagram.............................................................. 9

Figure 4. Model 300PM Loudspeaker Crossover Assembly top side etch layout diagram ........... 10

Figure 5. Model 300PM Loudspeaker Crossover Assembly bottom side etch layout ................... 11

Model 300PM Loudspeaker crossover assembly part list (per figures 4&5)............... 12

Model 300PM Loudspeaker part list (per figure 6) ......................................................... 13

Figure 6. Model 300PM Loudspeaker exploded view ................................................................... 13

Model 300PM Loudspeaker packing part list (per figure 7) ..........................................14

Figure 7. Model 300PM Loudspeaker packing diagram................................................................ 14

Model 300PM Loudspeaker Accessories........................................................................ 15

Figure 8. CB-22 bracket ................................................................................................................ 15

Figure 9. GBB-1 bracket ............................................................................................................... 15

Figure 10. GWS-200 bracket ........................................................................................................ 15

CAUTION: THE MODEL 300PM LOUDSPEAKER CONTAINS

NO USER-SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICING TO WARRANTY SERVICE STATIONS OR FACTORY SERVICE.

PROPRIETARY INFORMATION

THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF BOSE® CORPORATION WHICH IS BEING FURNISHED ONLY FOR THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT BY AN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE

BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED

FOR ANY OTHER PURPOSE.

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SPECIFICATIONS

External Dimensions: 12.83"L x 8.43"D x 7.25"H

(32.6cm x 21.4cm x 18.42cm)

Internal Cabinet Volume: 5.7 Liters (347 cu.in.) net Sensitivity (1W, 1m): 83.8dB SPL (calculated), free

field, per IEC-268-5 (for octaveband centered at 400Hz).

SmartProtect Circuit characteristics:

Turn-on voltage of the transistors of the electronic switch: 1.5-1.8 Vrms Turn-on level rise: 2-6 dB On resistance: <0.33Ω Maximum audio voltage applied to speaker: 60 Vrms Maximum continuous sinusoidal current: 3.4 Arms ±15% Reset Time: 250-300 ms

Port (each side): Flared slot port tuned to 60Hz. Impedance: 6Ω Nominal, 4.8Ω minimum from

20Hz to 20kHz.

Power Handling: 100W (24.5 Vrms) continuous

600W peak power handling w/SmartProtect circuit

Weight: 12.5 lb (5.7 kg) each Shipping Weight: 28 lb (12.7 kg) per packed pair

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SmartProtect Crossover PCB operation and troubleshooting

Note: Refer to Figure 3. Model 300PM Loudspeaker schematic diagram, for the following information.

The SmartProtect PCB is an electronic switch, in series with the drivers, used to protect the drivers from high current levels. It has a fast turn-on time of 100 milliseconds. At turn-on, current will flow through R16, R15, C2, D1, D2, C1, and R18. C2 and C3 form a virtual power supply which is used to provide operating voltage for the circuit as well as the bias for Q7 and Q8. This bias is limited by the zener diode D3 to 6.8 V. D1 and D2 form a voltage doubler. Once C2 is charged, Q9 will conduct and provide a charge path for C3. Once C3 is charged and the input audio voltage becomes lower than 1.5 Volts, Q9 will turn off. With Q9 shut off, the charge on C3 provides a voltage used to operate the circuit for up to 5 hours. R15 is a current sensing resistor. If current levels through it are too high, it will turn on either Q3 or Q4. This will pull the base of Q1 to the virtual ground, tripping the monostable multivibrator formed by Q1 and Q2. This will provide a 250 to 300 millisecond positive pulse to the base of Q5, turning it on for that amount of time. While Q5 is conducting, it will apply 0 Volts to the gates of Q7 and Q8, shutting them off and disabling the loudspeaker for that amount of time. Once the charging of C5 through R2 is completed, Q5 will shut off again, turning Q7 and Q8 back on, and allowing the speaker to operate again. If the overload condition persists, it will trip the circuit again after about 10 ms, shutting off the drivers again.

Troubleshooting

1. If PTC1 is open, the unit will not play at low volume levels (Vin < 1.5 Volts) when the system is first turned on, but as the volume is increased, the SmartProtect circuit will turn on, and the speaker will operate. It will then operate for 5 hours, until the charge on C3 is too low to keep the circuit running, and then the speaker will shut off again.

2. If either R18 or R16 is open, there will be no charge path for the virtual power supply formed by C2 and C3, and the circuit will never turn on. The symptom will be that the speaker will play at low volume levels (Vin < 1.5 Volts), but as the volume is turned up, the speaker will stop operating. This may also happen if for any reason Q7, Q8 or any other component in the circuit fails, and the internal safety “watchdog” C7 turns the Q5 on preventing the Q7 and Q8 from being overheated.

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DISASSEMBLY/ASSEMBLY PROCEDURES

Note: Refer to Figure 6 for the following

procedures.

1. Grille removal

1.1 Using your fingers, grasp the grille (1)

edge nearest the port slot and gently pull the grille away from the cabinet until it comes free.

1.2 Grasp the opposite edge of the grille and gently pull it away from the cabinet until it comes free as well.

2. Grille replacement

2.1 Orient the grille (1) so that the Bose

logo is aligned with the print on the rear of the cabinet.

2.2 Align the two grille posts on the curved grille edge with the cabinet grille socket grommets (4) and press the grille edge in place.

2.3 Align the two grille posts at the opposite grille edge with the cabinet grille socket grommets and press the grille in place. The grille should be neat and flush with the cabinet.

3. Driver removal

3.1 Remove the grille (1) using

procedure 1.

3.2 Using a phillips-head screwdriver, remove the three screws (2) that secure the driver (3) to the cabinet.

3.3 Using your fingers, grasp the plastic basket of the driver and pull gently. The driver should come free.

3.4 Note the driver wiring color code, and cut the wires as close to the terminals as possible.

4. Driver replacement

4.1 Observing polarity, solder the wires

from the crossover assembly (9) to the driver (3) terminals.

4.2 Orient the driver correctly into the cabinet and secure it using the screws (2) removed in procedure 3.2.

4.3 Replace the grille (1) using procedure 2.

5. Crossover Assembly removal

5.1 Remove the driver (3) located behind the curved portion of the grille (1) using procedure 3. Do not cut the wires to the driver.

5.2 Remove the batting behind the driver and retain it to reinstall later.

5.3 Using a long shaft phillips-head screwdriver, remove the four screws (8) that secure the crossover assembly (9) to the binding post connector (10).

5.4 Gently pull the crossover assembly straight off of the metal tabs on the binding post connector until it comes free. You can now slide the crossover assembly out through the driver opening.

5.5 Unsolder the wires from the crossover assembly.

6. Crossover Assembly replacement

6.1 Solder the driver (3) wires to the

appropriate locations on the crossover assembly (9).

6.2 Insert the crossover assembly through the driver opening.

6.3 Orient the crossover assembly so that the tabs on the binding post connector (10) and the receptacles on the crossover assembly are aligned.

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DISASSEMBLY/ASSEMBLY PROCEDURES (CONT.)

6.4 Gently slide the crossover assembly

onto the tabs on the binding post connector until it is seated.

6.5 Secure the crossover assembly using the four screws (8) removed in procedure 5.

6.6 Replace the batting removed in procedure 5.2.

6.7 Replace the driver (3) and grille (1) using procedure 4.

7. Binding Post Connector removal

7.1 Remove the grille (1), driver (3), and

crossover assembly (9) using procedure 5.

7.2 Remove the four screws (2) that secure the binding post connector (10) to the speaker cabinet.

7.3 Gently pull on the binding post connector housing until it comes free of the cabinet.

8. Binding Post Connector replacement

8.1 Slide the binding post connector (10)

into the rear of the cabinet. Be sure it is oriented so that the + and - markings on the binding post connector are nearest the edge of the cabinet.

8.2 Secure the binding post connector to the cabinet using the four screws (2) removed in procedure 7.2. Be sure not to overtighten the screws, or you will crack the binding post connector housing.

8.3 Reinstall the crossover assembly (9), driver (3), and grille (1) using procedure 6.

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TEST PROCEDURES

Frequency Generator

+ -

Power Amplifier

DMM

Loudspeaker

Figure 1. Model 300PM Loudspeaker test

setup diagram

Note: Refer to Figure 2. Model 300PM

driver wiring diagram for the following procedure.

1. Phase Test

1.1 Remove the speaker grille using

Disassembly/Assembly procedure 1.

2.4 Replace the grille using procedure 2.

3. Air Leak Test

3.1 Remove the grille using procedure 1.

3.2 Apply a 6Vrms, 60Hz signal to the

input terminals on the rear of the speaker cabinet. Leave the speaker port open.

3.3 Test duration should be 5 seconds minimum.

3.4 Listen carefully for air leaks along all glue joints, at the binding post connector, and at both transducer mounting locations. Air leaks will be heard as a hissing or sputtering sound. All repairs must be hidden.

3.5 Replace the grille using procedure 2.

1.2 Observing polarity, apply a +6Vdc level

to the input terminals on the rear of the loudspeaker. The drivers should both move outward.

1.3 Replace the grille using procedure 2. Note: Refer to Figure 1. Model 300PM

Loudspeaker test setup diagram, for the following tests.

2. Rub and tick test

2.1 Remove the grille using procedure 1.

2.2 Apply a 6Vrms, 10Hz signal to the

input terminals on the rear of the speaker cabinet.

2.3 Listen carefully for any buzzes, rattles, or other extraneous noises from the drivers or trim parts.

4. Power Sweep Test

4.1 Apply a 6Vrms, 10Hz signal to the

input terminals on the rear of the speaker cabinet. Leave the speaker port open.

4.2 Sweep the input frequency from 10Hz to 3kHz.

4.3 Reduce the input voltage level to 4Vrms and sweep the oscillator from 3kHz to 5kHz.

Note: The whooshing noise from the port at approximately 60Hz is acceptable.

4.4 Replace any transducer that has a buzzing noise. There shall not be any buzzes or rattles from the internal connecting wires or components. Redress any buzzing wires.

Note: There is a normal suspension noise. To distinguish between a rub or a tick and suspension noise, displace the driver cone slightly with a finger. If the noise stays the same, it is suspension noise.

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BLACK

DRIVER

PCB

RED

BLUE

DRIVER

Figure 2. Model 300PM Loudspeaker driver wiring diagram

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R19

RXEO25

PTC1

(0.25A, 3.0 OHMS)

R20

100K

10/25V

51K

FRONT

DRIVER

(RED)

1 W41

+ OUTPUT

PTC2

RXE040

(BLUE)

65uH

10/50V

(0.4A,1.3 OHM)

+6.8V

51K

2SA608K-E

10/25V

51K

20K

2SC536K-E

Q10

10K

R21

IRLI540G

S 3

R10

100K

2SC536K-E

560

2SC536K-E

51K

2SC536K-E

0.27

51K

R14

1N4148

R13

R12

1N4148

R11

1.5K

1N4148

R15

0.15

R16

S 3

IRLI540G

D 2

+ INPUT

DRIVER

ANGLED

(BLUE)

- OUTPUT

(BLACK)

R17

R18

20K

40K

1N3070

0.33/100V

200

1.0M

100pF

1N4148

2SA608K-E

1N4148

2SA608K-E

1N4736

100/25V

0.33/250V

1N3070

Figure 3. Model 300PM Loudspeaker schematic diagram

Notes: Unless otherwise specified

1. Resistor values are in Ohms.

- INPUT

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Figure 4. Model 300PM Loudspeaker Crossover Assembly top side etch layout diagram

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Figure 5. Model 300PM Loudspeaker Crossover Assembly bottom side etch layout

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Model 300PM Loudspeaker crossover assembly part list (per figures 4&5)

Reference

Designator

Description Part Number Qty per

Assy.

R1 Res, Metal Oxide, 1W, 5%, 39KΩ 171259-3935 1 R2 Res, CF, 1/4W, 5%, 1 MEGΩ 120968-1055 1 R3, R4, R17 Res, CF, 1/4W, 5%, 20kΩ 120968-2035 3 R5, R6, R7, R9, R19, Res, CF, 1/4W, 5%, 51kΩ 120968-5135 5 R8 Res, CF, 1/4W, 5%, 560Ω 120968-5615 1 R10, R20 Res, CF, 1/4W, 5%, 100kΩ 120968-1045 2 R11, R12, R13, R14 Res, CF, 1/4W, 5%, 1.5kΩ 120968-1525 4 R15 Res, Metal Oxide, 2W, 5%, .15Ω 177962-R155 1 R16 Res, Metal Oxide, 1W, 5%, 2kΩ 171259-2025 1 R18 Res, Fusing, 1/4W, 5%, 200Ω 130102-2015 1 R21 Res, CF, 1/4W, 5%, 10kΩ 120968-1035 1 C 1 Cap, Film, 85, 100V, 5%, .33uF 120388-334 1 C 2 Cap, Box, 85, 250V, 10%, .33uF 190483-334 1 C 3 Cap, El, 85, 25V, 20%, 100uF 119941-101E 1 C 4 Cap, Disc, SL, 50V, 10%, 100pf 137269-101 1 C5 Cap, Box, 85, 50V, 5%, .27uF 137127-274 1 C6, C7 Cap, El, BP, 85, 25V, 20%, 10uF 149948-100E 2 C8 Cap, El, BP, 85, 50V, 20%, 10uF 138365 1 L1 Inductor, 65 uH, .11 Ohm, Ferrite 189799 1 D3 Diode, Zener, 6.8V, 1W, 5%,

116995-4736A 1

1N4736

D4, D5, D6, D7, D8,D9Diode, Switching, 75V, 300mA

121501 6

1N4148

Q2, Q3, Q4, Q5, Q10 Transistor, Bi-polar, N, 60V, 200mA,

117921 5

TO-92, 2SC536K-E

Q1, Q6, Q9 Transistor, Bi-polar, P, 60V, 200mA,

119168 3

TO-92, 2SA608K-E D1, D2 Diode, Glass, 200V, .5W, 1N3070 190346 2 Q7, Q8 N-Channel, Hexfet, IRL1540G 190347 2 PTC1 Polyswitch, 60V, 4mm 190348-1 1 PTC2 Polyswitch, 60V, 4mm 191995-1 1 W5,W6 Connector, Terminal, 1 Pos, Female 147946 2 used with L1 Screw, Machine, 4-40x1, Pan, Xrec 103146-16 1 used with L1 Nut, Hex, 4-40 103234-440 1 used with L1 Washer, Flat, .141, #5 108258-05 1

PCB, Bare Board, 300PM 187255-001 1

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Model 300PM Loudspeaker part list (per figure 6)

Item

Description Part Number Quantity per

Number

1 Grille Assembly, 300PM 187239-001 1 2 Screw, Tapp, 8-11x.75,Pan, Xrc/Sq 17 2672-12 1 0 3 Driver Assembly, Shielded, 4.5” 187246-001 2 4 Grommet, Grille Socket 176068 4 5 Insert, Threaded, Ext/Intl 121690 4 6 Washer, Lock, .326, 5/16, Intl T 121692-31 4 7 Nut, Lock, Flange, M8 121691 4 8 Screw, Hilo, 6x.375, Pan/Xrec 175972-06 4 9 Crossover Assembly, 300PM 18 7241-001 1

10 Connector, Binding Post, 203, Grey 187232-003 1

- Nameplate, Logo, Black 187254-001 1

5 6 7

REF

(2X)

Assembly

REF

(4X)

(3X)

(2X)

(3X)

REF

(4X)

5 6 7

(2X)

LOGO NOT SHOWN

Figure 6. Model 300PM Loudspeaker exploded view

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Model 300PM Loudspeaker packing part list (per figure 7)

Item

Description Part Number Quantity per

Number

1 Packing, End Cap, 203 187243-001 2 2 Bag,Poly, 13.5x33.5x13x3 mil 106595 2 3 Carton, RSC, 300PM 187242-001 1

(2X)

Pair

Figure 7. Model 300PM Loudspeaker packing diagram

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Model 300PM Loudspeaker Accessories

There are three optional brackets that can be used to mount the Model 300PM Loudspeaker that are available through Bose BKK. They are model numbers CB-22, GWS-200, and GBB-1.

Note: All measurements are in millimeters; all angles are in degrees.

Figure 8. CB-22 bracket

Figure 9. GBB-1 bracket

Figure 10. GWS-200 bracket

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SPECIFICATIONS AND FEATURES SUBJECT TO CHANGE WITHOUT NOTICE

Bose Corporation The Mountain Framingham, Massachusetts, USA 01701

P/N 193626 REV. 00 08/97 FOR TECHNICAL ASSISTANCE OR PART ORDERS, CALL 1-800-367-4008