Arcam-Alpha9P-int-sm维修电路原理图.pdf
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1、ALPHA 9/9P SERVICE MANUALALPHA 9/9P SERVICE MANUALARCAM ALPHA 9/9P SERVICE MANUALIssue 1 Serial No. 001 - (Paul Newton July 96)Circuit DescriptionInput/Output SelectionThe Alpha 9 integrated amplifier has 6 line levelinputs and optional phono input selected by use ofthe motorised listen switch, SW20
2、1.The use of the record switch SW202 allowsrecording of one source whilst listening to another.The Processor/Tape 2 switch, SW207, allows tapemonitoring of a 3 head tape deck connected to theProcessor/Tape 2 sockets. It can also be used toallow input signals to be routed to an externalsurround decod
3、er for processing before beingrouted back to the Alpha 9. Tone Control & Preamp Out/Power Amp InThe tone control stage on the Alpha 9 is basedaround a dual op-amp Z2. The first half providesa buffer stage for the tone controls and the secondone with its frequency dependent feedback is usedas the ton
4、e control itself.The output of the tone control then passes throughthe balance control RV201 and then onto thepower amp stages and the preamp out bufferstage formed by Z203.The tone controls and balance pot can bebypassed by use of the direct switch SW205.The Alpha 9 can be driven from an externalpr
5、eamplifier source by moving the internal switchSW206 to disconnect the Alpha 9 preamp stagesfrom the power amp.Power AmplifierThe signal from either the Alpha 9 input sockets oran external preamp enters the power amp stagevia C12 and R35. Q11, Q16 form a long, tailed pair driven by thecurrent source
6、 formed by Q18 and Q19.Q6 is the Class A stage driving the quasicomplementary output stage of Q4, Q5, andmosfets Q1, 2.The Alpha 9 and Alpha 9P utilize an auto biascircuit to maintain the correct quiescent current(IQ). The circuit works by monitoring the voltageacross the 0.22 ohm resistors R1, RA1
7、andcomparing it to a voltage derived from the - 44v railvia R24. Both these voltage are fed into the inputsof comparator Z3. If the voltage across the 0.22ohm resistors increases the output of thecomparator goes high impedance and Q15 isturned off. This causes capacitor C72 to dischargeand reduce th
8、e bias on the base of Q17 whichreduces the IQ. Conversely if the voltage acrossthe 0.22 ohm resistors is low then Q15 is turned onmore and C72 charges and increases the bias onQ17 and so increases the IQ. Under signalconditions a low frequency, variable mark/spaceratio, waveform can be seen on the c
9、ollector oftransistor Q20 as the bias is being automaticallyadjusted. Z1 is a d.c. servo used to maintain a low d.c. offsetat the speaker outputs.Power SuppliesThe Alpha 9/9P is powered by a toroidaltransformer with 2 sets of secondary windings.The main windings are used to provide +/-44VD.C. after
10、rectification and smoothing by diodesD201-204 inc. reservoir capacitors C201, 202.The second winding is rectified to provide anunregulated supply voltage for the motor driver ics,Z402 (for the volume control) & Z403 (for the listenselector).This unregulated supply is also smoothedand regulated with
11、a simple stabilizer circuit (zenerdiode D402 and associated components) toprovide a stable voltage for the micro controllerZ401.Protection/ Mute circuit The protection and mute functions are carried outby Z501. This performs turn on delay, d.c. offsetdetection and thermal cutout. It also displays th
12、estatus of the amplifier with the use of a bicolourLED - Green for ready and Amber for when thespeakers are disconnected internally because of afault condition or on initial power up whilst the 5second switch on delay mute is operating.If the unit suffers a current overload the protectioncircuit may
13、 latch and the unit will not reset until ithas been switched off and on again. If theprotection is activated by a thermal problem theunit will begin to operate again when it has cooleddown.The thermal cut out operating point is set by thethermistor TH501, mounted close to the outputdevice heatsinks.
14、Disc Stage (optional)RadioFans.CN 收音机爱 好者资料库ALPHA 9/9P SERVICE MANUALALPHA 9/9P SERVICE MANUALThe optional phono stage board available for theAlpha 9 provides amplification and RIAAequalization for both moving coil (MC) and movingmagnet (MM) cartridges.Transistors Q2-5 and their associated component
15、sprovide the extra gain required for moving coilcartridges when required Z1 forms a flat responsegain stage with the gain set by R3 and R4. R5 andC2 provide a low pass filter used as the highfrequency part of the RIAA de-emphasis. Thenegative feedback loop around IC2, R7, 8, 9, 10and C3 provides the
16、 active low frequency RIAA de-emphasis. The pcb mounted switch selects between MM or MC.The board is powered by +/- 15V regulated rails fromthe main pcb and the +15V rail is then regulated to6.3V by Q1 and D1, D2 to power the moving coilstage.Disassembly For Servicing1.Remove the top cover and front
17、 panel.2.Remove 2 screws securing the sub front to thechassis sides and 3 screws holding thesubfront to the chassis base.3.Remove 3 screws holding the pcb to thechassis. These can be found close to the largeheatsink and also near to the mains inletsocket.4.Remove 5 screws from the rear panel, one at
18、each end and 3 along the bottom edge.5.Remove the transformer bolt.The pcb, with the rear panel, transformer andsubfront attached, can now be pulled backwards outof the unit.TEST POINTDC VOLTAGETP1+ 5VTP2+9.6VTP30V MUTE ON +2V MUTE OFFTP40V VOL UP +5V VOL DOWNTP5+5V VOL UP 0V VOL DOWNTP6+15VTP7-15VT
19、P8+44VTP9-44VTEST POINTDC VOLTAGETP100.5VTP110.5VTP12-2VTP13-2VTP14+2.2VTP15+2.2VTP16+6.8VTP170V MUTE ON +2V MUTE OFFThe IQ voltage measured across the 0.22 ohmresistors R1, RA1 or R101, RA101should be about 6-7 mV.RadioFans.CN 收音机爱 好者资料库ALPHA 9/9P SERVICE MANUALALPHA 9/9P SERVICE MANUALAlpha 9 Inte
20、grated Amplifier Parts ListRef. No.DescriptionPart No.C1ELST 100U 25V2N710C2PEST 47N 63V 5%2K347C3ELST 100U 100V2N710BC4PCRB 100N 100V 5% RA 5mm2H410C5PPRO 680P 5% 63V RA2D168C6PSTY 56P 160V ENCAP 1PF%2F056C7ELST 10U 50V2N610C8ELST 100U 25V2N710C9PEST 15N 63V 5%2K315C10PEST 15N 63V 5%2K315C11PPRO 22
21、0P 5% 63V RA2D122C12ELST NON POLAR 10UF 35V2U610C13NPPRO 220P 5% 63V RA2D122C14NPPRO 220P 5% 63V RA2D122C15NELST 10U 50V2N610C16NPCRB 100N 100V 5% RA 5mm2H410C17NPCRB 100N 100V 5% RA 5mm2H410C18NPPRO 100P 63V 5% RA2D110NC19NPPRO 100P 63V 5% RA2D110NC20PEST 15N 63V 5%2K315C21NELST 10U 50V2N610C22PCRB
22、 100N 100V 5% RA 5mm2H410C23PCRB 100N 100V 5% RA 5mm2H410C25NPPRO 2N2 5% 63V RA2D222C26NELST 10U 50V2N610C71ELST 10U 50V2N610C72ELST 100U 25V2N710C101ELST 100U 25V2N710C102PEST 47N 63V 5%2K347C103ELST 100U 100V2N710BC104PCRB 100N 100V 5% RA 5mm2H410C105PPRO 680P 5% 63V RA2D168Alpha 9 Integrated Ampl
23、ifier Parts ListRef. No.DescriptionPart No.C106PSTY 56P 160V ENCAP 1PF%2F056C107ELST 10U 50V2N610C108ELST 100U 25V2N710C109PEST 15N 63V 5%2K315C110PEST 15N 63V 5%2K315C111PPRO 220P 5% 63V RA2D122C112ELST NON POLAR 10UF 35V2U610C113NPPRO 220P 5% 63V RA2D122C114NPPRO 220P 5% 63V RA2D122C115NELST 10U 5
24、0V2N610C116NPCRB 100N 100V 5% RA 5mm2H410C117NPCRB 100N 100V 5% RA 5mm2H410C118NPPRO 100P 63V 5% RA2D110NC119NPPRO 100P 63V 5% RA2D110NC120PEST 15N 63V 5%2K315C121NELST 10U 50V2N610C122PCRB 100N 100V 5% RA 5mm2H410C123PCRB 100N 100V 5% RA 5mm2H410C125NPPRO 2N2 5% 63V RA2D222C126NELST 10U 50V2N610C17
25、2ELST 100U 25V2N710C173ELST 100U 25V2N710C201ELST 10m 50V RA 32mm2N910C202ELST 10m 50V RA 32mm2N910C205PPRO 4N7 63V 5% RA2D247NC206PPRO 4N7 63V 5% RA2D247NC207ELST 10U 50V2N610C208ELST 10U 50V2N610C209ELST 10U 50V2N610C210ELST 10U 50V2N610C301NCERD 1N0 63V 20% RA2A210C401NELST 1M0 25V2N810ALPHA 9/9P
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