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 MANUAL ARCAM ALPHA 9/9P SERVICE MANUAL Issue 1 Serial No. 001 - (Paul Newton July 96) Circuit Description Input/Output Selection The Alpha 9 integrated amplifier has 6 line level inputs and optional phono input selected by use of the motorised listen switc
2、h, SW201. The use of the record switch SW202 allows recording of one source whilst listening to another. The Processor/Tape 2 switch, SW207, allows tape monitoring of a 3 head tape deck connected to the Processor/Tape 2 sockets. It can also be used to allow input signals to be routed to an external
3、surround decoder for processing before being routed back to the Alpha 9. Tone Control & Preamp Out/Power Amp In The tone control stage on the Alpha 9 is based around a dual op-amp Z2. The first half provides a buffer stage for the tone controls and the second one with its frequency dependent feedbac
4、k is used as the tone control itself. The output of the tone control then passes through the balance control RV201 and then onto the power amp stages and the preamp out buffer stage formed by Z203. The tone controls and balance pot can be bypassed by use of the direct switch SW205. The Alpha 9 can b
5、e driven from an external preamplifier source by moving the internal switch SW206 to disconnect the Alpha 9 preamp stages from the power amp. Power Amplifier The signal from either the Alpha 9 input sockets or an external preamp enters the power amp stage via C12 and R35. Q11, Q16 form a long, taile
6、d pair driven by the current source formed by Q18 and Q19. Q6 is the Class A stage driving the quasi complementary output stage of Q4, Q5, and mosfets Q1, 2. The Alpha 9 and Alpha 9P utilize an auto bias circuit to maintain the correct quiescent current (IQ). The circuit works by monitoring the volt
7、age across the 0.22 ohm resistors R1, RA1 and comparing it to a voltage derived from the - 44v rail via R24. Both these voltage are fed into the inputs of comparator Z3. If the voltage across the 0.22 ohm resistors increases the output of the comparator goes high impedance and Q15 is turned off. Thi
8、s causes capacitor C72 to discharge and reduce the bias on the base of Q17 which reduces the IQ. Conversely if the voltage across the 0.22 ohm resistors is low then Q15 is turned on more and C72 charges and increases the bias on Q17 and so increases the IQ. Under signal conditions a low frequency, v
9、ariable mark/space ratio, waveform can be seen on the collector of transistor Q20 as the bias is being automatically adjusted. Z1 is a d.c. servo used to maintain a low d.c. offset at the speaker outputs. Power Supplies The Alpha 9/9P is powered by a toroidal transformer with 2 sets of secondary win
10、dings. The main windings are used to provide +/-44V D.C. after rectification and smoothing by diodes D201-204 inc. reservoir capacitors C201, 202. The second winding is rectified to provide an unregulated supply voltage for the motor driver ics, Z402 (for the volume control) & Z403 (for the listen s
11、elector).This unregulated supply is also smoothed and regulated with a simple stabilizer circuit (zener diode D402 and associated components) to provide a stable voltage for the micro controller Z401. Protection/ Mute circuit The protection and mute functions are carried out by Z501. This performs t
12、urn on delay, d.c. offset detection and thermal cutout. It also displays the status of the amplifier with the use of a bicolour LED - Green for ready and Amber for when the speakers are disconnected internally because of a fault condition or on initial power up whilst the 5 second switch on delay mu
13、te is operating. If the unit suffers a current overload the protection circuit may latch and the unit will not reset until it has been switched off and on again. If the protection is activated by a thermal problem the unit will begin to operate again when it has cooled down. The thermal cut out oper
14、ating point is set by the thermistor TH501, mounted close to the output device heatsinks. Disc Stage (optional) RadioFans.CN 收音机爱 好者资料库 ALPHA 9/9P SERVICE MANUALALPHA 9/9P SERVICE MANUAL The optional phono stage board available for the Alpha 9 provides amplification and RIAA equalization for both mo
15、ving coil (MC) and moving magnet (MM) cartridges. Transistors Q2-5 and their associated components provide the extra gain required for moving coil cartridges when required Z1 forms a flat response gain stage with the gain set by R3 and R4. R5 and C2 provide a low pass filter used as the high frequen
16、cy part of the RIAA de-emphasis. The negative feedback loop around IC2, R7, 8, 9, 10 and C3 provides the active low frequency RIAA de- emphasis. The pcb mounted switch selects between MM or MC. The board is powered by +/- 15V regulated rails from the main pcb and the +15V rail is then regulated to 6
17、.3V by Q1 and D1, D2 to power the moving coil stage. Disassembly For Servicing 1.Remove the top cover and front panel. 2.Remove 2 screws securing the sub front to the chassis sides and 3 screws holding the subfront to the chassis base. 3.Remove 3 screws holding the pcb to the chassis. These can be f
18、ound close to the large heatsink and also near to the mains inlet socket. 4.Remove 5 screws from the rear panel, one at each end and 3 along the bottom edge. 5.Remove the transformer bolt. The pcb, with the rear panel, transformer and subfront attached, can now be pulled backwards out of the unit. T
19、EST POINTDC VOLTAGE TP1+ 5V TP2+9.6V TP30V MUTE ON +2V MUTE OFF TP40V VOL UP +5V VOL DOWN TP5+5V VOL UP 0V VOL DOWN TP6+15V TP7-15V TP8+44V TP9-44V TEST POINTDC VOLTAGE TP100.5V TP110.5V TP12-2V TP13-2V TP14+2.2V TP15+2.2V TP16+6.8V TP170V MUTE ON +2V MUTE OFF The IQ voltage measured across the 0.22
20、 ohm resistors 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 MANUAL Alpha 9 Integrated Amplifier Parts List Ref. No.DescriptionPart No. C1ELST 100U 25V2N710 C2PEST 47N 63V 5%2K347 C3ELST 100U 100V2N710B C4PCRB 100N 100V 5% RA 5mm2H
21、410 C5PPRO 680P 5% 63V RA2D168 C6PSTY 56P 160V ENCAP 1PF%2F056 C7ELST 10U 50V2N610 C8ELST 100U 25V2N710 C9PEST 15N 63V 5%2K315 C10PEST 15N 63V 5%2K315 C11PPRO 220P 5% 63V RA2D122 C12ELST NON POLAR 10UF 35V2U610 C13NPPRO 220P 5% 63V RA2D122 C14NPPRO 220P 5% 63V RA2D122 C15NELST 10U 50V2N610 C16NPCRB
22、100N 100V 5% RA 5mm2H410 C17NPCRB 100N 100V 5% RA 5mm2H410 C18NPPRO 100P 63V 5% RA2D110N C19NPPRO 100P 63V 5% RA2D110N C20PEST 15N 63V 5%2K315 C21NELST 10U 50V2N610 C22PCRB 100N 100V 5% RA 5mm2H410 C23PCRB 100N 100V 5% RA 5mm2H410 C25NPPRO 2N2 5% 63V RA2D222 C26NELST 10U 50V2N610 C71ELST 10U 50V2N61
23、0 C72ELST 100U 25V2N710 C101ELST 100U 25V2N710 C102PEST 47N 63V 5%2K347 C103ELST 100U 100V2N710B C104PCRB 100N 100V 5% RA 5mm2H410 C105PPRO 680P 5% 63V RA2D168 Alpha 9 Integrated Amplifier Parts List Ref. No.DescriptionPart No. C106PSTY 56P 160V ENCAP 1PF%2F056 C107ELST 10U 50V2N610 C108ELST 100U 25
24、V2N710 C109PEST 15N 63V 5%2K315 C110PEST 15N 63V 5%2K315 C111PPRO 220P 5% 63V RA2D122 C112ELST NON POLAR 10UF 35V2U610 C113NPPRO 220P 5% 63V RA2D122 C114NPPRO 220P 5% 63V RA2D122 C115NELST 10U 50V2N610 C116NPCRB 100N 100V 5% RA 5mm2H410 C117NPCRB 100N 100V 5% RA 5mm2H410 C118NPPRO 100P 63V 5% RA2D11
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