BBK SW-8, SW-10, SW-12 Service Manual

PHOENIX

SW - 8

SW - 10

SW - 12

Service Manual

SW-8 Principle ans Servicing

1. Block diagram of the player

Block diagram of the player is shown in the figure 1.1:

7PHOENIX SUB

R L SW GND

INPUT BOARD

~29 ~14 GND

TRANSFORMER

~14 ~29

INPUT BOARD

R L SW GND

PHASE CONTROL

LPF FILTER

1 2V

SW1

G ND

+12 V

S W1

G ND

-1 2V

+12 V

Frequency adjust

3PHOENIX

LPF FILTER

Volume adjust

AMPLIFIER OUTPUT

R&L CONECT BOARD

R SPEAKER SW POWER AMPLIFIER

L SPEAKER

~29 ~14 GND ~14 ~29

POWER SUPPLY

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CPHOENIX

SW SPEAKER

AMPLIFIER BOARD

Figure 1.1 Block diagram of the player

2. SW-8 working principle

SW-8 is composed of a bass loudspeaker and left/right channel loudspeaker; signals input from

input board; left and right channel signals (L, R) directly output to left and right loudspeaker; bass

signals (SW) perform pre-amplifying processing through 4558 and fulfil phase and volume control, and

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Then input to power amplifying circuit of power amplifier board. SW signals perform differential

amplifying through the differential circuit composed by V301 V304, and then perform composite power

amplifying through rear stage triode and output to bass loudspeaker.

To protect bass loudspeaker, this player has over-voltage and over-current protection circuit.

Protection method is that disconnect loudspeaker output through disconnecting relay Y301 when

protection starts up.

A over-voltage sampling circuit is connected on SW output end which is composed of R353 and

R337. When output central point of a channel is over +4.3V or lower than -4.3V DC voltage, V318 or

V317 is on to make their C electrode voltage decrease, V319 is also on and finally relay disconnects and

loudspeaker output is disconnected. Over-current protection principle is the same with that of over-

voltage, a over-current sampling triode V313 is connected on output load resistor and load resistance is

R323, R324. When over-current trouble appears, voltage drop that produces on R323, R324 will

increase quickly, once it exceeds B electrode voltage of V303, V313 is on and V319 is also on, finally

relay is connected and loudspeaker output is disconnected.

3 Function introduction to 4558

(1) Description

The RC4558 and RM4558 devices are dual general-purpose operational amplifiers with each half

electrically similar to the A741 except that offset null capability is not provided.

The high common-mode input voltage range and the absence of latch-up make these amplifiers

ideal for voltage-follower applications. The devices are short-circuit protected and the internal frequency

compensation ensures stability without external components.

The RC4558 is characterized for operation from 0?C to 70?C, and the RM4558 is characterized for

operation over the full military temperature range of 55 C to 125 C.

(2) FEATURES

Continuous-Short-Circuit Protection

Wide Common-Mode and Differential

Voltage Ranges. No Latch-Up

No Frequency Compensation Required

Low Power Consumption

Unity-Gain Bandwidth . . . 3 MHz Typ

Gain and Phase Match Between Amplifiers

Low Noise . . . 8 nV?Hz Typ at 1 kHz

Designed To Be Interchangeable With

Raytheon RC4558 and RM4558 Devices

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PIN No Symbol I/O Description

1 1OUT O Output 1

2 1IN– I Inverting Input Pin 1

3 1IN+ I Non-Inverting Input Pin 1

PIN No. Symbol I/O Description

4 V CC– I Negative Pow er Supply

5 2IN+ I Non-Inverting Input Pin 2

6 2IN– I Inverting Input Pin 2

7 2OUT O Output 2

8 V CC+ I Positive Pow er Supply

(3) PIN CONFIGURATION

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4. PCB Board

(1) signal Board

R101

R102

C107

C106

C111

R103

R104

C105 C104

C112

N101

R106 RP101

C108

C103

R105

RP102

C102

C101

C109

R107

3PHOENIX-0

C110

051110

XP3

OUT

+12 -12G

XS4

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+ 11 hidden pages