Pioneer SPEC-2 서비스 매뉴얼 - 페이지 9

{카테고리_이름} Pioneer SPEC-2에 대한 서비스 매뉴얼을 온라인으로 검색하거나 PDF를 다운로드하세요. Pioneer SPEC-2 50 페이지. Pioneer spec-2 stereo power amplifier operating instructions
Pioneer SPEC-2에 대해서도 마찬가지입니다: 사용 설명서 (17 페이지)

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Power Switch OFF Muting

Since +B3 normally passes from R7 to R6 and

flows to -B.2, Q28 base is maintained at cut off

potential. When the power switch is tumed OFF,

-B2 immediately ceases, since its time constant is

smaller than

+83.

Consequently, +83

passes

through Dl and is applied to Q28 base, tuming

Q28 ON. Point B potential then falls rapidly,

tuming Q27 and Q30 OFF.

lmpedance Selector Muting

When the impedance selector switch (S1) is

changed from 8Sl to 4Sl, uncharged capacitor C2

is introduced into the - 82 circuit, temporarily

reducing -B2 voltage. This causes Q28 to switch

ON, C1 to be discharged, and Q29 & Q30 to be

switched OFF.

SPEG.El

Although Q28 switches OFF again, Q29 and Q30

continue in the OFF condition for several seconds

while C1 is charging.

Temperature Detector

The temperature detector employs positive coeffi-

cient thermistors (posistors). These are temperature

sensitive elements possessing a positive temperature

response, rapidly increasing in resistance when a

certain temperature is exceeded (see Figs. 8 & 9).

The posistors (TH3 & TH4) are mounted on the

power transistor. If some abnormality increa.ses

the temperature to the posistor operating point,

their

resistance rapidly

increases, reducing the

potential at point C. This allows DB to conduct,

so that the potential at point D drops and Q27

switches ON.

, 2

p o i n t

-Tem0erature

t ("

Fig. 8 Posistor-temperature Response

Fig. 9 Temperature Detector Circuit