Arcam-A65-int-sm维修电路原理图.pdf

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1、A65/75 DiVA A65, A75 & P75 Plus Amplifi ers Service Manual ARCAMARCAM Issue 1.0 RadioFans.CN 收音机爱 好者资料库 Contents List ! Contents list ! Circuit description ! Service guide ! Circuit diagrams ! Component overlays ! Circuit board parts list ! General assembly parts list RadioFans.CN 收音机爱 好者资料库 A65/75/

2、75P Plus Circuit Description PSU In order get the output devices to turn fully on and achieve the greatest efficiency, an auxiliary rail is formed from a charge pump driven by the main AC outputs from the transformer. C304,305 & D301,302 charge on alternate cycles. In the other cycle the charge on C

3、304,305 is pumped into C310,311 respectively. This creates a voltage much greater than the standard rails, but with low regulation and high ripple. This is then regulated to 38V via emitter followers Q300,302,303,305 from a zener stabilized voltage (D304,305) The Pre-amp 15V supply comes from linear

4、 regulators Z300,301. The transformer is a dual voltage unit, the required voltage being selected by which fuse holder is fitted with the appropriate fuse. If an alternative to 115V or 230V is required then a different transformer is fitted. The secondary is centre tapped for the main rails, but a s

5、eparate winding is added for the uC supply. The star ground point SP300 is not a component on the PCB and is on the schematic only for layout purposes. Pre-amp The direct signal path (line in, tone controls defeated) consists of a single op-amp gain stage, buffering the j-fet input multiplexers and

6、Tape Monitor and AV switches. The selected input is AC coupled to the op-amp, the output is DC to the Pre-out, via a j-fet pre-mute switch. This switch is controlled by the uC in such a way that when ever the output relay changes state signal is removed from the power amplifier (A65/75). The MM phon

7、o stage (by passable A75 only, SW100) is opamp based. The circuit is AC coupled to give RIAA/IEC low frequency response. The cartridge is loaded by R100,101,C119,120. The 1kHz gain is 56dB, and RIAA eq set by R110,112,111,113,C127,129,128,130. Each line input has static protection afforded by the ba

8、ck to back diodes (e.g. D101,103), and RF filtering is set by R118,C134 etc. The selected input is buffered for Tape output by Z104 set as a follower. The output resistor is inside the feedback loop so to keep the output impedance low and short protection is catered for. C121,122 maintain stability

9、into capacitive loads. From the tape monitor switch (Z105) onwards the signal is AC coupled (C151,152). From there the signal is fed to the tone controls. These consist of two stages: Balance and buffer (Z160), and Bass/Treble Z161. The output of this stage is again AC coupled. Switch SW162 selects

10、whether the tone adjusted signal or a direct signal reaches the gain section. In the A75 Z164 can be used to bypass the volume control when AV input is selected. This fixes the gain to allow an external AV processor to control the volume setting. The gain stage (Z163) has a gain of 2.2, and the same

11、 low impedance output arrangement as the Tape output. The signal from this stage to the Pre- amp outputs and the Power amp input is controlled by a pre-mute (Z171). This removes thumps and clicks, and in the case of the Power amp relay changing state, removes signal so arcing will not take place. Po

12、wer Amplifier The new topology is a high gain voltage feedback design, with a bipolar output stage. Its signal path is designed to be fully symmetrical, despite not having a symmetrical circuit (symmetrical rail to rail). This is achieved with a new dual differential input gain block, where the inpu

13、t differential sees a symmetrical active load (Q600,601,700,701) before driving the second voltage amplification stage (VAS) differential (Q603,604,703,704). This could be described as two Wilson mirrors with their bases clamped together. The second differential also has an active load of a more tra

14、ditional mirror (Q610,611,710,711), and this gives a push pull signal to the input of the output stage, improving on the traditional single ended current source of the often called blameless topology. The input pair (Q606,607,618,619,706,707,718,719) are in a Darlington configuration to lower input

15、current offset which in turn will lower DC offset at the output, as the impedances seen on the input nodes are necessarily high for the wide bandwidth required. The output stage is a simple bipolar darlington (Q614,615,714,715). However, the devices used are Darlington devices with integral diodes.

16、This means the bias temperature compensation is part of the output device enabling smaller number of devices, no extra devices on the heatsink (vital for this mechanical layout) and more consistent temperature compensation of bias. Also the resistors are also integral, saving a large amount of PCB r

17、eal estate and hand insertion cost, while also able to be used as bias set test points and protection sensing. Due to the decreased efficiency of this type of output stage over the previous bootstrapped Mosfet output, a separate set of rails is required for the VAS stage in order to saturate the out

18、put transistors. The operation of this is outlined in the Power supply section. However, these rails are individually regulated for each channel to decrease power supply crosstalk. The protection of the output stage is taken care of by a proprietary IC (Z101). This takes care of the switch on delay

19、(R150,C149), DC offset (R102,103,C147), Thermal trip (TH100), and safe operating area. The safe operating area is monitored by a network which compensates for the voltage across the output devices, current through them, and duration of power (R627,606,625,605,C617 & symmetrical associated components

20、) and this is sent to the protection IC via (Q605,612,613,616,617,712,713,716,717). The output of the protection IC is sent to the micro controller (uC) to signal the output relay (RLY1) status. Also, for output muting purposes, the uC can switch the relay via Q100. Input Selection The uC controls t

21、he operation of the unit. IR commands are received from RX900 on a break-off PCB found on the front panel and fed via LK900/LK903 3-way ribbon. On power on/off the current state of the pre-amp switching stored in an EEPROM Z906. The input switching is 5V logic level and is direct from the uC to the

22、DPDT analogue switches in the case of Tape Monitor (Z105), AV (Z164,A75 only), Pre-mute (Z171) and Mute Q100. The source selector is achieved by 8 way analogue multiplexors (Z102,103) and the control signals are decoded from the uC from MUX1,2,3 by Z907 which also drives the appropriate front panel

23、LED. The input selection is set by the remote control or the rotary encoder on the front panel display PCB. Tape monitor and AV mode(A75 only) is set by SW900. Volume Control The volume control is a motorized manual type, where the signals are routed through the 8-way ribbon LK189. The motor drive c

24、omes from Z905, which is a logic level controllable motor driver. It has its own unregulated PSU (D907,C920),and the speed of the volume knob is dictated by the REF pin. The circuit (Q900,R905,901,C901) allows the speed to vary from just above stall to full as the volume control button is depressed

25、on the remote. SIM Module The connector PL161 (P75 only) allows the fitting of the ARCAM SIM module. In order to allow this to operate LK172 & LK173 must be removed. This will allow 12V trigger signals to operate the P75. Headphones The Speaker outputs (SK600,700) are connected to the headphone sock

26、et (SK162) via an 8-way ribbon LK170,171. The output is attenuated by a resistor network R161,162,236,237. The Relay drive is fed through the headphone sockets switch (HPSW1,2) so that when headphones are inserted the speakers are disconnected. Switch SW163 allows the separate switching of the secon

27、d speaker terminals on SK600,700. A65, A75 & P75 Service Guide Fault diagnostics Fault Action No power Check mains fuse Check transformer connections Check power supply rails Stuck in protection Check power supply rails Check protection circuit voltages Check for dry joints on o/p devices Intermitte

28、nt audio on one channel Check for dry joints around o/p devices Fails to respond to commands Check supply to remote circuit Check IC Z900 Check remote flex foil cable Check for dry joints on selector pcb Volume control rubs on front panel Pull knob out from fascia Audio crackles on o/p Check for com

29、ponent break down using hot air gun & freezer spray Check transformer connections Power supply test points Position Voltage LK125 +37 volts DC LK126 -37 volts DC LK271 or black speaker terminal 0 volts LK303 +15 volts DC LK301 - 15 volts DC Q300 emitter +38 volts DC Q304 emitter +38 volts DC Q302 em

30、itter -38 volts DC Q305 emitter -38 volts DC D910 emitter +5 volts DC remote supply IQ settings Model IQ setting Comments - (22/01/02) A65 37mV A75 37mV P75 37mV A85 12mV Set for 8.5mV cold, reset for 12mV when warm P85 12mV Set for 8.5mV cold, reset for 12mV when warm A65 plus 12 to 15mV A75 plus 1

31、2 to 15mV P75 plus 12 to 15mV Hints & tips ! To isolate a fault between pre and power stage remove C602 (left channel) or C702 (right channel). ! Always check and re-solder o/p device SAP15N and SAP15P pin connections. ! Replace Z900 IC if software version is below version 3 ( note version 82 is als

32、o ok ). ! Make sure R127 is not touching LK130. ! When replacing the top cover with a new top it may be necessary to re-drill the fixing holes. ISSUE DRAWING NO. DRAWING TITLE DATE Filename: ECO No.DESCRIPTION OF CHANGE L942C1_1.0.PRJ A65 PLUS AMP Contact Engineer: L942C1 11-Dec-2001 INITIALS Printe

33、d:17Sheetof Notes: Contact Tel:(01223) 203 200Travis Pierce A & R Cambridge Ltd. Pembroke Avenue Cambridge CB5 9PB Waterbeach PWRLEFT PROTECTION A1 SP2_SEND_L SP2_RETN_L OP_L A1 LEFT CHANNEL L942C5_1.0.SCH ACLT1 MUTE AVCONTROL TAPECONTROL MUX1 MUX2 MUX3 PREMUTE PROT SENSE REMOTE CONTROL L942C7_1.0.S

34、CH SELOPR SELOPL MUX1 MUX2 MUX3 TAPECONTROL ACSENSE PROT_OP_L PROT_OP_R PROTECTIONMUTE HPSW2 HPSW1 TAPOL TAPOR PROT SENSE PHONO & INPUTS L942C3_1.0.SCH ACSENSE ACLT1 POWER SUPPLY L942C2_1.0.SCH PWRRIGHT A1 SP2_RETN_R OP_R SP2_SEND_R A1 RIGHT CHANNEL L942C6_1.0.SCH PWRLEFT PWRRIGHT SELOPR SELOPL HPSW

35、2 AVCONTROL HPSW1 SP2_SEND_L SP2_RETN_L OP_L OP_R SP2_SEND_R SP2_RETN_R PREMUTE TAPOR TAPOL PROT_OP_R PROT_OP_L TONE CONTROL L942C4_1.0.SCH TGP12/12/01PRODUCTION RELEASE1.0 USE exlude A65 FILTER FOR BOM 01_E020 TOP SHEET FOR A65 L942AY ISSUE DRAWING NO. DRAWING TITLE DATE Filename: ECO No.DESCRIPTIO

36、N OF CHANGE L942C5_1.0.SCH A65 PLUS AMP Contact Engineer: L942C5 11-Dec-2001 INITIALS Printed:57Sheetof Notes: Contact Tel:(01223) 203 200Travis Pierce A & R Cambridge Ltd. Pembroke Avenue Cambridge CB5 9PB Waterbeach Q600 BC556B Q601 BC556B Q604 2SA970GR Q606 BC546B Q607 BC546B R617 680R MF R619 10

37、K MF R618 10K MF R613 47R MF R614 47R MF R612 100K MF R600 1K0 MF PWRLEFT Q611 2SC2240GR Q610 2SC2240GR R620 10K MF Q603 2SA970GR Q608 BC546B Q609 BC546B +C601 100U EL 100V + C600 100U EL 100V 0V_HF +C616 10U EL L600 2U2H LAC SMALL R631 2R2 CF R630 4R7 W2 CF D603 1N4003F +37V -37V C621 470P CD RLY1A

38、 RLY G5Z-2A-E C620 470P CD C622 1N0 CD SPLD600 SPLS600 PD6 OP_L SP2_SEND_L SP2_RETN_L R616 2K7 MF R611 100K MF C603 100P PPW 0V_SIG 0V_HF 0V_SIG 0V_HF Q612 2SC2240GR R627 430R MF R606 100R MF R605 100R MF R625 6K8 MF R622 10K MF R621 680R MF R629 47K MF +C617 10U EL Q605 BC556B A1 PROTECTION D604 1N

39、4003F R628 430R MF R626 6K8 MF + C618 10U EL R608 100R MF R607 100R MF A1 D605 1N4148 D606 1N4148 0V_LS_L 0V_LS_L Q602 BC556B R615 47R MF R601 100R MF R602 100R MF R603 100R MF R604 100R MF SPLE600 Left Channel Power Amplifier Q614 SAP15N Q615 SAP15P D600 4V7 400MW 0V_HF 0V_HF 0V_HF 0V_HF Q616 2SA97

40、0GR D601 ZENER 400MW 27V D602 ZENER 400MW 27V R610 100R MF R609 100R MF R623 10K MF Q613 BC546B R624 10K MF C608 100P PPW C607 100P PPW Q619 BC546B Q618 BC546B R633 12K MF R632 12K MF + C602 22U SILMIC 2 + C605 100U SILMIC 2 +38V_L -38V_L C604 100P PPW 0V_LS_L Bias-L + Bias-L - 21mm x 32mm SELF ADHE

41、SIVE E852MC Q2 PAD SP600 Q2-PAD-SAP 21mm x 32mm SELF ADHESIVE E852MC Q2 PAD SP601 Q2-PAD-SAP C609 22N CD CL600 E856MC CL601 E856MC TGP12/12/01PRODUCTION RELEASE1.0 Q617 ZTX653 +C624 100U 25V ZA EL R634 470K MF + C625 10U EL SET BIAS TO 12mV 01_E020 C623 100N PE 100V C610 100N PE 100V C613 100N PE 10

42、0V C611 100N PE 100V C612 100N PE 100V C614 100N PE 100V C615 100N PE 100V C619 100N PE 100V RV600 220R PSET +C603 100U 50V YXF LOW Z +C626 100U 50V YXF LOW Z Top+ Top- SK600A SPKSKT_G Bot+ Bot- SK600B SPKSKT_G CHASS SK600C SPKSKT_G HS600 E81801-75 HS601 E81801-75 HS602 E81801-75 HS603 E81801-75 USE

43、 exlude A65 FILTER FOR BOM ISSUE DRAWING NO. DRAWING TITLE DATE Filename: ECO No.DESCRIPTION OF CHANGE L942C7_1.0.SCH A65 PLUS AMP Contact Engineer: L942C7 11-Dec-2001 INITIALS Printed:77Sheetof Notes: Contact Tel:(01223) 203 200Travis Pierce A & R Cambridge Ltd. Pembroke Avenue Cambridge CB5 9PB Wa

44、terbeach WARNING SAFETY CRITICAL COMPONENT REPLACE WITH IDENTICAL PART uC, Volume Drive & Remote Control C912 10N CD C900 10N CD R900 1R0 FU D906 1N4003F D907 1N4003F + C920 1M0 25V C913 10N CD MOTE900 P900 +5v VOLUME DRIVEMOTOR DRIVER +5V GND 1 MD1 2 CC1 3 REF 4 MC1 5 MC2 6 VCC1 7 VCC2 8 CC2 9 MD2

45、10 Z905 BA6109 12 VOLMOT900 1Y271 ACLT1 MUTE MUX1 MUX2 MUX3 AVCONTROL TAPECONTROL R915 220R MF A0 1 A1 2 A2 3 VSS 4 SDA 5 SCL 6 WP 7 VDD 8 Z906 24C01 C917 100N CD X900 CST4.00 C918 100N CD +C914 220U EL +5v +5v +5v C919 100N CD 1 2 3 SW900A 2PCO_NON_LAT 4 5 6 SW900B 2PCO_NON_LAT R912 100K MF +C921 1

46、0U EL D910 1N4148 R913 10K MF +5v +5V R914 4K7 MF 0V_DIG 0V_DIG 0V_DIG 0V_DIG 0V_DIG 0V_DIG0V_DIG 0V_DIG 0V_DIG 0V_DIG 0V_DIG 0V_DIG 0V_DIG VDD 16 GND 8 Z907B 74HC4051 R904 10R MF + C915 100U EL PREMUTE 0V_DIG +5V MOTSUP900 VOLM901 VOLM900 REMO900 C916 100N CD 1 2 3 LK903 3WAY CABLE HOLDER D911 1N41

47、48 1 2 3 4 5 6 7 8 9 10 SK900 FFC10V R902 100R MF R903 100R MF 0V_DIG 0V_DIG PROT SENSE Disp A Disp B Disp C Disp D Disp E Disp F Disp G Disp H Disp I R901 12K MF Q900 BC556B +5v R905 33K MF + C901 100U EL D908 ZENER 5V1 400MW X0 13 X1 14 X2 15 X3 12 X4 1 X5 5 X6 2 X7 4 INH 6 A 11 B 10 C 9 VEE 7 X 3

48、 Z907A 74HC4051 TGP12/12/01PRODUCTION RELEASE1.001_E020 1 3 2 LK900 L856CA REMOTE SENSOR SNAP OFF BOARD +5V 3 O/P 2 GND 1 Case Case O/P GND+5V RX900 PIC-26043TM2 IR RX SUPPORT PAD SP1 IR RX SUPPORT PAD PB5 1 PB4 2 PA3 3 PA2 4 PA1 5 PA0 6 PB3 7 PB2 8 PB1 9 PB0 10 VSS 11 (TMR)/INT 12 PC0 13 PC1 14 PC2

49、 15 PC3 16 PC4 17 PC5 18 RES 19 VDD 20 OSC1 21 OSC2 22 PA7 23 PA6 24 PA5 25 PA4 26 PB7 27 PB6 28 Z900 HT48R30 28-DIP-B-0 USE exlude A65 FILTER FOR BOM ISSUE DRAWING NO. DRAWING TITLE DATE Filename: ECO No.DESCRIPTION OF CHANGE L942C3_1.0.SCH A65 PLUS AMP Contact Engineer: L942C3 11-Dec-2001 INITIALS Printed:37Sheetof Notes: Contact Tel:(01223) 203 200Travis Pierce A & R Cambridge Ltd. Pembroke Avenue Cambridge CB5 9PB Waterbeach 3 2 1 Z100A NE5532 C119 100P PP R100 47K MF R108 470R MF C124 47P