Arcam-Alpha10-pwr-sm维修电路原理图.pdf

ALPHA 10/10P SERVICE MANUALALPHA 10/10P SERVICE MANUAL1ALPHA 10/10P SERVICE MANUALCIRCUIT DESCRIPTIONThe mother PCB is common for both the A10 and A10P with the exception of the input mode switch and pre-ampoutput mute relay which are only fitted to the A10 and the power/standby LED and links to parallel the inputconnections to what would otherwise be the pre-amp output for use with a mono link. The amplifier is based on theD290/Alpha 9 design but with lower gain, a higher current and higher voltage driver stage and a high power outputstage. The current servo has been improved over the Alpha 9 to be output device independent. A micro supervisesthe amplifier state, switch state and remote control functions. Provision is made for an additional 3rd channel PCB tobe added with power supply and protection circuitry access.Input stageThe input connections are taken either from the pre-amp connector, LK12X, or the external power amp input on theA10 depending on the position of SW1. On the A10P, the input is taken from the external power amp input only withprovision for a mono shorting link by having two parallel input connectors. On the A10, there is a mute relay on thepre-amp outputs which are always connected to the pre-amp connector, LK12X.The signal is passed through a low pass filter with a -3dB point of 550KHz at normal gain and 740KHz at low gain.The gain is selected by SW2. C72 and C74 are d.c. blocking capacitors with a -3dB point of 0.7Hz. A d.c. errorcorrection current is injected into the base of Q19 and 26 from the voltage servo Z3 and 4, to null any voltage offset atthe amplifier output.The input and voltage amplifier stages both run off regulated 15 Volt suppies. The input stage is an NPN differentialinput, Q18, 19, 25 and 26, with an adjustable current source, Q21 and 28 which sets the quiescent current through allthe stages but specifically the output stage. C37, R58, C49 and R66 keep the input stage and voltage amplifier stable.Q52, 53, 54 and 55 form a current mirror to ensure that the differential input is balanced during normal operation.Voltage AmplifierThe voltage amplifier consists of another differential pair, Q48, 49, 50 and 51. Q48 and 50 are the positive pulling sideof the voltage amplifier output and Q49 and 51 pull negative via a current mirror Q8, 9, 10 and 11. The network C12,36, R74 and 77 give the current mirror gain to compensate for the fact that Q49 and Q51 is only driven from the low-impedance side of the input stage current mirror. The network ensures a fast, symmetrical slew rate of the voltageamplifier stage.Network C69, 70, R172, 174 ensure the overall stability of the amplifier by reducing the open loop gain at highfrequencies.Second Voltage Amplifier and Driver StageQ33, 36, 41 and 44 are the next voltage amplifier stage with feedback applied from the output coupled to theiremitters. This stage runs on the full supply rail voltages and splits the level shifts the signal via Q2, 3, 5 and 6 to drivethe gates of the output MOSFETs, Q13, 14, 15 and 16. Q2 and 3 simply buffer the inverted signal at the collector ofQ36 to drive the low side MOSFETs, Q13 and 15. Q5 and 6 invert the inverted signal at the collector of Q41 and Q44to drive the high side MOSFETs, Q14 and 16. To ensure that the high side drive is able to swing far enough to ensurethe high side MOSFETs can be driven to saturation, a bootstrap, C5, D41 R57, C78 and D22 boosts the driver stagepower supply during positive excursions of the amplifier output. This is inactive at low output voltage swings as anydistortion induced by the network would be more audible at such levels.Output StageBoth the high and low side output devices feature over-current protection, Q17, 23, 24, 30 which clamps the gate ofthe MOSFET it protects. A high current is permitted through the MOSFET for a few milliseconds after which time thecurrent is throttled down to about 10A peak. A second current sensing network, Q32 and Q35 activates theover-current protection cut-out if the low side is current limiting for too long, a few hundred milliseconds. The currentsensing resistors do not reduce the transconductance of the MOSFETs because the driver stage is referenced to theMOSFET source. This means that the current through the driver stage is also sensed but this is insignificant as fas asover-current protection sensing is concerned.Auto-biasRadioFans.CN 收音机爱 好者资料库ALPHA 10/10P SERVICE MANUALALPHA 10/10P SERVICE MANUAL2Figure 1Block Diagram of Power AmplifierSense ResistorComparitor OutputMeasured Current (blue)Other MOSFET-ve MOSFET50%49%52%Bias correctUnder BiassedOver BiassedFigure 2 Auto-bias under dynamic conditionsThe bias is regulated in two modes, one where these is no signal and one when signal is being split between the highand low side MOSFETs when driving a alternating signal into a load.Under static conditions, Z8 simply compares the sensed current, which includes the driver stage current, with a d.c.mode reference of 13mV. The sense resistor is 0.11 so this corresponds to a current of about 120mA, some of whichis driver current. The current through the MOSFETs is about 80mA at this point. The comparator output is level shiftedto drive the integrating current servos Z3 and 4. This adjusts the amplifier current so that, on average, the bias level isheld at the reference point.Under dynamic conditions, the low side drive will definitely be conducting more current than the reference (80mA) forhalf the signal cycle and will be switched off for the other half. The result is a rectangle wave output from thecomparator, Z4.When the output stage is biassed correctly (class AB operation) the comparator output toggles when the currentthrough the sense resistor for the -ve MOSFET is equal to the d.c. mode static reference level and at the half waypoint of the signal. The result is a perfect square wave output from the comparator. Under these conditions, the +veMOSFET is also conducting the same amount of current at this point. If the bias level is lower than the reference, say,at zero (class B operation) then the -ve MOSFET will spend slightly less than half the time conducting at or above thereference level resulting in a rectangle wave output from the comparator at a duty cycle slightly less than 50%. If thebias level is higher than the reference then the -ve MOSFET will spend slightly more than half the time conducting ator above the reference level resulting in a rectangle wave output at a duty cycle slightly more than 50%. The changein duty cycle away from 50% causes the integrator, Z3 and Z4 to adjust the bias level via the bias adjustingtransistors, Q22 and 29.The integrator has a reference, the a.c. mode dynamic reference, for a bias point slightly higher than for a 50% dutycycle. This eliminates the possibility of the bias being slowly throttled due to component tolerance mismatch resultingin a reference which would pull the servo down. A high dynamic bias reference level simply stabilises the bias slightlyhigher than the static reference but a low dynamic reference causes the bias to drift down to complete throttle.This system works if the signal is a.c., symmetrical and is not a rectangle wave. Certainly, only a.c. signals are passedRadioFans.CN 收音机爱 好者资料库ALPHA 10/10P SERVICE MANUALALPHA 10/10P SERVICE MANUAL3Figure 3 Micro Block Diagramthrough the amplifier due to C72 and 74 d.c. blocking capacitors and on average the signal will be symmetrical. Anyshort-term asymmetry will be ironed out by the long time constant of the integrator. Main Power SupplyThe main power supply is regulated in two stages. First it is pre-regulated by Q1 and 4 to about 11V less than themain supply rails. This supply is made available to an option board. The maximum load on these supplies is 150mAfor less than 2W dissipation in Q1 and 4. These supplies are then regulated to +/-15V by Z1 and 2. These supplies areused by the input stages of the power amplifiers including any 3rd channel board, the pre-amplifier board and anoptional phono amplifier board. The positive voltage regulator, Z1, has a larger heatsink than Z2 because the phonoboard consumes much more current from the positive rail than from the negative rail.Control MicroThe control micro performs the following functions.Switches the amplifier on or off,Mutes the speakers #1 or #2 or the pre-amp output,Monitors the heatsink temperature,Monitors RF content of speaker outputs,Handles the remote bus and infra red remote input,Reports fault conditions to the main display and LED,Reads the speaker and power switch positions. The control micro runs of the constant power supply from standby transformer, TX2. This enables the amplifier to beswitched on or off remotely from the remote bus or, in the case of the integrated amplifier, from an infra red remotecontrol. This power supply is intended to supply all the digital circuitry in the amplifier including any option boards.This is supplied at 8V to the other boards where it will be locally regulated to 5V as required.The micro communicates with the display board via a multi-master I2C bus. This bus is used to report amplifier andpower status to the display micro and remote control commands received. It is also possible for the display micro tocontrol functions on the power amplifier board. The option board also uses this bus to receive any remote controlcommands and communicate with the display micro.The external remote bus handles raw information from infra red sensors with no demodulating. The remote bus inputcan be echoed to the output through a buffer circuit. The incoming signal is demodulated by Z13. Raw signal is alsosent to the micro interrupt line, pin 12, for assessing the noise on the remote bus. In addition, any d.c. signal on theremote bus is sensed on pin 2 of the micro in when it is not being used as an output to mute the hardware remoteecho buffer. The micro must modulate any output it sends to this bus with a carrier (37KHz). The output will drive oneor two series infra red LEDs directly.The list below shows how various fault conditions can be deduced simply from the Power LED behaviour.ALPHA 10/10P SERVICE MANUALALPHA 10/10P SERVICE MANUAL4On power up, the protection should be engaged. This is checked after 3 seconds on pin 9 of Z9. If it isnthappening, the unit shuts down with flashing red.If the protection does not clear after about 16 seconds on power-up the unit shuts down to flashing red. Thisis usually caused by a voltage offset.Any main amp power loss detected on pin 26 after power-up causes a shut down to flashing red.Any RF detected on pin 3 results on immediate shut down to flashing red.Any protection fault detected after power up on pin 9 results in a flashing amber LED for about 16 secondsmax. If it has not cleared by then the unit is shut down to flashing red. Protection faults are caused by voltageoffset or over-current. Over-current should latch resulting in a shut down after 16 seconds. Voltage offsetsshould clear themselves if brief.A temperature fault on pin 25 results in the power LED flashing slow amber and can last indefinitely until itclears. When it clears the flashing will speed up until the protection times back in. ALPHA 10P POWER AMP MAIN BOARD PARTS LISTRef No.DescriptionPart NoC1ELST 100U 100V2N710BC2ELST 100U 100V2N710BC3MLC 100N 50V X7R 10% SM2C410C4ELST 100U 100V2N710BC5ELST 100U 100V2N710BC6ELST 22U 63V2N622C7ELST 10U 50V2N610C8ELST 22U 63V2N622C9ELST 10U 50V2N610C10ELST 10U 50V2N610C11ELST 1U0 50V2N510C12PPRO 4N7 63V 5% RA2D247NC13SUPPR CAP 4N7 250V2K247C14PPRO 150P 5% 63V RA2D115C15ELST 10U 50V2N610C16ELST 10U 50V2N610C17ELST 10U 50V2N610C18ELST TNC 10m 63V RA 40mm2N910AC19ELST TNC 10m 63V RA 40mm2N910AC20PPRO 4N7 63V 5% RA2D247NC21PPRO 4N7 63V 5% RA2D247NC22ELST 100U 25V2N710C23ELST 100U 25V2N710C24ELST 100U 25V2N710C25ELST 100U 25V2N710C26ELST 100U 25V2N710C27ELST 100U 25V2N710C28MLC 470P 100V NPO 5% SM2C147C29MLC 470P 100V NPO 5% SM2C147C30MLC 470P 100V NPO 5% SM2C147C31MLC 100N 50V X7R 10% SM2C410C32ELST 22U 63V2N622C33ELST 22U 63V2N622C34MLC 100N 50V X7R 10% SM2C410C35PPRO 150P 5% 63V RA2D115C36PPRO 4N7 63V 5% RA2D247NC37PPRO 1N0 5% 63V RA2D210C38PPRO 680P 63V 5% RA2D168C39PPRO 680P 63V 5% RA2D168C40MLC 10N 50V X7R 10% SM2C310C41MLC 10N 50V X7R 10% SM2C310C42MLC 10N 50V X7R 10% SM2C310C43MLC 10N 50V X7R 10% SM2C310C44SUPPR CAP 4N7 250V2K247C45ELST 10U 50V2N610C46SUPPR CAP 4N7 250V2K247C47SUPPR CAP 4N7 250V2K247C48ELST 3M3 25V2N833C49PPRO 1N0 5% 63V RA2D210C50ELST 1U0 50V2N510C51ELST 220U 16V2N722C52ELST 220U 16V2N722C53ELST 220U 16V2N722C54ELST 220U 16V2N722C55PCRB 100N 100V 10% RA 5mm2H410C56PCRB 100N 100V 10% RA 5mm2H410C57PCRB 100N 100V 10% RA 5mm2H410C58PCRB 100N 100V 10% RA 5mm2H410C59PCRB 100N 100V 10% RA 5mm2H410C60PCRB 100N 100V 10% RA 5mm2H410C61PPRO 100P 63V 5% RA2D110NALPHA 10/10P SERVICE MANUALALPHA 10/10P SERVICE MANUAL5C62PPRO 100P 63V 5% RA2D110NC63PPRO 150P 5% 63V RA2D115C64PPRO 330P 5% 63V RA2D133C65PPRO 150P 5% 63V RA2D115C66PPRO 330P 5% 63V RA2D133C67PEST 15N 63V 5%2K315C68PEST 15N 63V 5%2K315C69PSTY 56P 160V ENCAP 1PF%2F056C70PSTY 56P 160V ENCAP 1PF%2F056C71ELST NON POLAR 10UF 35V2U610C72ELST NON POLAR 10UF 35V2U610C73ELST NON POLAR 10UF 35V2U610C74ELST NON POLAR 10UF 35V2U610C75PEST 47N 63V 10%2K347C76PEST 47N 63V 10%2K347C77PEST 47N 63V 10%2K347C78PEST 47N 63V 10%2K347C79ELST NON POLAR 10UF 35V2U610C80ELST NON POLAR 10UF 35V2U610C81MLC 22P 100V NPO 5% SM2C022C82MLC 22P 100V NPO 5% SM2C022C83ELST 100U 25V2N710C84MLC 100N 50V X7R 10% SM2C410C85MLC 100N 50V X7R 10% SM2C410C86MLC 100N 50V X7R 10% SM2C410C87MLC 100N 50V X7R 10% SM2C410C88MLC 100N 50V X7R 10% SM2C410C89MLC 100N 50V X7R 10% SM2C410C90ELST 10U 50V2N610C91PPRO 680P 63V 5% RA2D168C92MLC 10N 50V X7R 10% SM2C310C93MLC 1N0 50V X7R 10% SM2C210C94MLC 10N 50V X7R 10% SM2C310C95ELST 10U 50V2N610C96ELST 10U 50V2N610C97MLC 100N 50V X7R 10% SM2C410C98MLC 10N 50V X7R 10% SM2C310C99CERD 10PF 63V 10%2A010C100CERD 10PF 63V 10%2A010D1ZENER 15V 400MW3C11504D2ZENER 15V 400MW3C11504D3ZENER 10V 400MW3C11004D4ZENER 10V 400MW3C11004D5ZENER 10V 400MW3C11004D6ZENER 10V 400MW3C11004D7ZENER 10V 400MW3C11004D8ZENER 10V 400MW3C11004D9ZENER 10V 400MW3C11004D10RECTIFIER 6A40 6A 400V3B6A40D11RECTIFIER 6A40 6A 400V3B6A40D12RECTIFIER 6A40 6A 400V3B6A40D13RECTIFIER 6A40 6A 400V3B6A40D14RECTIFIER 1N4003F 1A 200V3B4003D15RECTIFIER 1N4003F 1A 200V3B4003D16SSDIODE 1N4148 75V3A4148D17SSDIODE 1N4148 75V3A4148D18RECTIFIER 1N4003F 1A 200V3B4003D19RECTIFIER 1N4003F 1A 200V3B4003D20SSDIODE 1N4148 75V3A4148D21RECTIFIER 1N4003F 1A 200V3B4003D22RECTIFIER 1N4003F 1A 200V3B4003D23RECTIFIER 1N4003F 1A 200V3B4003D24RECTIFIER 1N4003F 1A 200V3B4003D25RECTIFIER 1N4003F 1A 200V3B4003D26SSDIODE 1N4148 75V3A4148D27RECTIFIER 1N4003F 1A 200V3B4003D28SSDIODE 1N4148 75V3A4148D29ZENER 4V7 400MW3C04704D30SSDIODE 1N4148 75V3A4148D31SSDIODE 1N4148 75V3A4148D32SSDIODE 1N4148 75V3A4148D33SSDIODE 1N4148 75V3A4148D34SSDIODE 1N4148 75V3A4148D35SSDIODE 1N4148 75V3A4148D36SSDIODE 1N4148 75V3A4148D37S