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Excellent manual, detailed, very useful! Exactly what I needed, I'd recommend it to all who need it. Although images are scanned easily readable and explicit. A valuable tool product at a price more than modest, take it with confidence and you will not regret it!
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Clear and complete service manual. Easy now to restore my old Kenwood KD-1500.
Thanks a lot.
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Thanks for this "hard to find" service manual. This Sony PS212A is a very good turntable that needed to be restored !
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Excellent quality on these manuals. Same as having the original printed manual and incredibly useful when doing a custom install like me. Keep it up on the good work.
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This is an excellent information source. Great quality and tons of info regarding technical service for the Technics SH8065.
3. ADVANTAGE OPERATION AND OF POWER AMPLIFIER CIRCUITRY SECTION
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QThere is neccessity to decrease not the phase response till DC rangein order to increase the musicsignalresponse of extremely low frequencyrange. Therefore, amplifier is this employingno capacitors exceptonesfor phase compensation, and has an almostperfecttransient characteristics. OThe first stageFET(2SK97) a dual FETof even characterisis tics and has a large Cm and no-leakage currentat normal temparature. To avoid the influenceby temperature drift, such as center voltage(0V) deviation, this FETis used as differentialamplifier and operatesat cross point which is the optimum point of drain current(at about 3mA) against the temperature drift. QTransistors, TR05and TR07,the push-pull pre-driverstage functionsas currentdifferential amplifierthat the stabilized operationcan be obtained. In addition,the collector current of these transistors enough high to make linearity is excel lent. OSincethis Amplifier employsphaseadvancer circuits [C06, C08, C15, R29, C16 and R30J,which have not been frequently used,to compensate the phasecharacteristics on high frequencyrangeand is also made to have enough
3-1. Advantage
current on each stage to increase the through-rate, the performance on high frequency range is conspicuously improved. OTo avoid the voltage deviation, regulatedpower supply circuit composedof ZD0'1, ZD02 is employed.
3-2. Operation
The use of differentialamplificationat first stagedual FET, (FET01, FET02) and connectionof the FETto the differential amplifier composedof TR01,TR02,make possibleto obtain enoughgainand remarkable low distortion. The output signalsof TR0'1 and TR02are untiphase. The output signalof TR02addsto TR05,on the other hand, the output phaseof TRO1 invertedbyTR03,then,it becomes is input signalof TR04and TROZwhich cascoded are connection. The output signals TR05and TR07are inphase at that the operationof this stageis push-pulldrive and currentdifferential amplification.The power amplifierof the f inal stageis composed of SEPP (SingleEnded push-pull)symmetry comple mentaryin 3-stage darlingtonconnectiontype. TR@and TR10arecomposing currentlimitercircuitto protect power transistor from break-down overload. by
4. ADJUSTMENTS
4-1. Driver Circuit BoardAdjnstments (Seethe picture of top view on page 3.)
N o t e :1 . M a s t eV o l u m e . . . . . . r 1. Room Temperature. ......Minimum 3. For adjustment, run the unit for more than 3 minutesafter the power is switchedon.
suBfEcr ,or,r"r*, |
DC Volt Meter Sameas above
MEASURE OUTPUT Speaker Terminal Sameas above
ADfusr I oolrrr ro*
F-2721 vR01, vR02 F-2722 VRO1, VRO2 F-2721 VRO3
CONDITION " Set VR01 and VR02 to center oosition. o Then, for the purpose of proceeding the accurateadjustment, set the voltaeeto 0 volt by VR01first and V-RO2 next. o By turning VR03counterclockwise, the-bias current is decreased gradually.
D C0 V + 5 m V
DC 0V+5mV
Sameas above
T PT e r m i n a + ) ( - ) (l ot F-2721 of F-2723
DC 20mV+1mV
Sameas above T PT e r m i n a + ) ( - ) (l
F-2722 VRO3
DC 20mV+1mV
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