Arcam-AVR400-avr-sm维修电路原理图.pdf

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1、AVR400 Service Manual Issue 1RadioFans.CN 收音机爱 好者资料库2314ITEM NO.PART No.DESCRIPTIONQTY1TGP3523 / TGP3524FASCIA BLACK / SILVER12TGP3526 / TGP3527COVER BLACK / SILVER13HA4V06STORX SCREW M4 x 644TGP3535FRONT PCB ASSY18055TOLERANCES UNLESS 0.000.10OTHERWISE STATED 0.0 0.20ANGULAR TOL. +2 DEGREES07090ALL

2、 DIMENSIONS INMILL METERS UNLESSOTHERWISE STATED20EF6DATE:DRAWN BY:13FA3A4CHECKED BY:4MATERIAL:BCDRAWING TITLE10A30ORIGINAL SCALE 1:4FINISH:85022876DSHT 1 OF 47A & R CAMBRIDGE LTDPART NUMBER AND DRAWING NUMBERD2342560E10013BC40DATECHG.ZONEDESCRIPTION OF CHANGEREL.DR.CHK.-ECO NR.-MCM9-4-2011MGBAVR400

3、 MAIN ASSEMBLYCOVER + FASCIA-RadioFans.CN 收音机爱 好者资料库123ITEM NO.PART No.DESCRIPTIONQTY1TGP3539TRANSFORMER - POWER12FAN 80 x 80 x 25mm23FAN MOUNTING BRACKET28055TOLERANCES UNLESS 0.000.10OTHERWISE STATED 0.0 0.20ANGULAR TOL. +2 DEGREES07090ALL DIMENSIONS INMILL METERS UNLESSOTHERWISE STATED20EF6DATE:D

4、RAWN BY:13FA3A4CHECKED BY:4MATERIAL:BCDRAWING TITLE10A30ORIGINAL SCALE 1:4FINISH:85022876DSHT 2 OF 47A & R CAMBRIDGE LTDPART NUMBER AND DRAWING NUMBERD2342560E10013BC40DATECHG.ZONEDESCRIPTION OF CHANGEREL.DR.CHK.-ECO NR.-MCM9-4-2011MGBAVR400 MAIN ASSEMBLYFANS + TRANSFORMERS-14235SOLDERED TOPOWER AMP

5、 PCBITEM NO.PART No.DESCRIPTIONQTY1TGP3534CHASSIS ASSY12TGP3543VIDEO PCB ASSY13TGP3538POWER AMP PCB ASSY14TGP3544FOOT45TGP3540TRANSFORMER - STANDBY18055TOLERANCES UNLESS 0.000.10OTHERWISE STATED 0.0 0.20ANGULAR TOL. +2 DEGREES07090ALL DIMENSIONS INMILL METERS UNLESSOTHERWISE STATED20EF6DATE:DRAWN BY

6、:13FA3A4CHECKED BY:4MATERIAL:BCDRAWING TITLE10A30ORIGINAL SCALE 1:4FINISH:85022876DSHT 3 OF 47A & R CAMBRIDGE LTDPART NUMBER AND DRAWING NUMBERD2342560E10013BC40DATECHG.ZONEDESCRIPTION OF CHANGEREL.DR.CHK.-ECO NR.-MCM7-9-2010MGBAVR400 MAIN ASSEMBLYPOWER PCBs + FEET-1245637ITEM NO.PART No.DESCRIPTION

7、QTY1TGP3528REAR PANEL ASSY12TGP3536INPUT PCB ASSY - MAIN13TGP3543 (part)INPUT PCB ASSY - ETHERNET14TGP3543 (part)INPUT PCB ASSY - CONNECTORS15TGP3537HDMI PCB ASSY - MAIN16TGP3543 (part)HDMI PCB ASSY - VIDEO17TGP3529AM/FM TUNER18055TOLERANCES UNLESS 0.000.10OTHERWISE STATED 0.0 0.20ANGULAR TOL. +2 DE

8、GREES07090ALL DIMENSIONS INMILL METERS UNLESSOTHERWISE STATED20EF6DATE:DRAWN BY:13FA3A4CHECKED BY:4MATERIAL:BCDRAWING TITLE10A30ORIGINAL SCALE 1:2.5FINISH:85022876DSHT 4 OF 47A & R CAMBRIDGE LTDPART NUMBER AND DRAWING NUMBERD2342560E10013BC40DATECHG.ZONEDESCRIPTION OF CHANGEREL.DR.CHK.-ECO NR.-MCM9-

9、4-2011MGBAVR400 MAIN ASSEMBLYREAR PANEL + PCBs-AVR400 Power Amplifier Circuit DescriptionApart from the power transformer, the power amplifier electronics is fully contained on the large double sided PTH PCB and heatsink located at the bottom of the AVR400. This is called the Main Board on the schem

10、atic diagrams (pages 11 and 12). The Main Board also contains the mains input circuitry, in-cluding the safety fuses and standby power transformer, so great care should be exercised when probing this area of the board.Note that some small surface mount components are soldered to the underside of thi

11、s PCB.The 7 power amplifiers are identical in terms of circuitry, although necessary compromises in the physi-cal layout may give rise to slight differences in measured noise, crosstalk and distortion performance. The two channels at the extreme ends of the heatsink have less radiating area availabl

12、e to them and will run hotter under load this is not normally an issue as these are assigned to the SBL and SBR channels. Looking from the rear of the AVR, facing the flat face of the heatsink, the channel order is SBR, SR, FR, C, FL, SL and SBL, the same order as the loudspeaker terminals. The SBL

13、and SBR channels can also be assigned to zone 2 or as duplicates of the FL and FR channels for when passively biamping the main stereo loudspeakers. In this latter condition we recommend assigning the SBL and SBR outputs to the tweeters of the FL and FR speakers, in order to minimize the power ampli

14、fiers heat dissipation.Note that the 8 pre-amplifier outputs are also on this PCB apart from SUB their phono sockets are effectively in parallel with the power amplifier inputs, which are fed from the Input Board via a ribbon cable and CON103. This connector also carries 5 power supply and power amp

15、lifier control signals to and from the system microprocessor (P) IC151 situated on the Input Board above the Main Board.The amplifiers power supply is provided from a centre-tapped secondary winding on the toroidal power transformer, via the connector BN508, to the bridge rectifier D5830. This is mo

16、unted on a small PCB near the top of the heatsink. The rectified AC is then sent to the main PCB via connectors BN581/582. To avoid induced hum and distortion it is important to keep these cables twisted tightly together and well away from the actual power amplifier circuitry. The main 15,000F 80V r

17、eservoir capacitors, C835 and C836, are positioned on the main PCB well away from the power amplifier input traces and close to the system star ground. The smoothed DC is fed to the power amplifiers Vcc and Vee lines near the centre of the heatsink via a twisted-pair cable, again to minimize inducti

18、on into the power amplifiers. Vcc and Vee are typically +/- 52V at 234VAC with no signal. Q5845 sends a fraction of Vcc to the muting control on the Input Board.The FL (front left) channel will now be described in detail.The input stage is a long tailed pair Q5101 and Q5102, with local degeneration

19、provided by R5105 and R5107. The tail is fed from the negative rail via an approx 3mA ring-of-two constant current source, Q5109 and Q5110. R5101 and C5101 at the input provide high frequency rolloff and help keep residual DAC ultrasonic noise above 100kHz out of the power amplifier. DC blocking is

20、provided by C5102 at the input and C5107 in the feedback loop so that the whole power amplifier has unity gain at DC. The midband AC gain is 22000/680 = 32.35 after allowing for the attenuation provided by R5101 and R5102. Thus 875mV at the input produces 100W into 8 ohms at the output.The long tail

21、ed pairs collectors are loaded by a current mirror, Q5103 and Q5104. The resistors R5103/4 and R5105/6 are 1% tolerance to minimize even order distortion. The collector of Q5101 also feeds the Darlington class A voltage amplifier stage (VAS) made up of Q5115 and Q5116. Q5113 is loaded by the output

22、stage and the 8mA constant current source made up by Q5125 and Q5126. The amplifiers main frequency compensation network (for stability) comprises C5115 plus the combination of C5116 and R 5115. This adds gain inside the loop (two pole compensation) at high audio frequencies so that the additional f

23、eedback further reduces high frequency distortion and crossover distortion within the audio band.These stages are partially decoupled from the Vcc and Vee power supplies by D5130/R5130/C5130 and D5129/R5129/C5129 respectively. They are also bootstrapped to the amplifier output via the networks R5118

24、/C5128/R5128 and R5117/C5127/R5127. This raises the supply lines by approximately 3V at full output to avoid clipping the driver stage prematurely.The output stage comprises classic complementary emitter followers Q5150/Q5170 (NPN) and Q5160/Q5180 (PNP). The On Semiconductor output transistors have

25、a current gain that is sustained to about 10 amps and a very large safe operating area, which allows the amplifiers to drive low impedances well. They also have built-in thermal compensation diodes which helps stabilize the quiescent current both statically (when hot) and dynamically (when playing m

26、usic at high level) this minimizes crossover distortion and improves sound quality.The output stage biasing is performed in the network around the amplified diode Q5120, which is mounted in intimate thermal contact with the driver transistor Q5130, plus the two built-in diodes associated with the ou

27、tput transistors. The thermistor R5122 is positioned on the PCB close to the heatsink and provides extra downward compensation at very high temperatures. Bias is set by VR51 and is largely independent of temperature it should be set to16-20mV when measured across the outer terminals of the compound

28、emitter resistor R5175, using the 2 pin connector CN51, 5 minutes or more after the AVR400 is powered up. The power amplifier output is routed across the PCB to the back panel. It includes a Zobel network (sometimes called a Boucherot cell) R5183/C5183 and a series inductor L5185 damped by a 4.7R 2W

29、 re-sistor R5184. These components help isolate the amplifier from reactive loads to ensure high frequency stability. One half of the normally-off relay RL52 is used to switch the load in and out.Each power amplifier is protected against overload in a number of ways. The complementary transistors Q5

30、130 and Q5131 protect the NPN half of the output stage and Q5140 and Q5141 the PNP half. They operate as Sziklai pairs, passing negligible current until a threshold voltage of approx 600mV is reached across R5132 and R5142. Between 600 and 700mV the pairs then ramp up current smoothly, diverting it

31、away from the bases of Q5150 and Q5160 to limit the output stage drive to a safe level, within the power transistors SOA (safe operating area). The 600mV threshold voltage depends upon both the instantane-ous current and voltage across the output transistors, set by the networks R5132/R5136/R5137/R5

32、138/R5175 for the top half and R5142/R5146/R5147/R5148/R5175 for the bottom half. R5135/R5145 and the zener diodes D5135/D5145 change the slope of the protection locus at high Vce voltages. R5134/R5135 plus C5134/C5145 prevent fast transients and brief overloads from prematurely triggering the prote

33、c-tion. The above dual slope SOA protection is self resetting but if a gross overload persists for more than a second or two (such as when a channels output is short circuited with music playing at a moderate to loud level) then the open collector transistor Q5181 sinks current for long enough to in

34、itiate the ampli-fiers full shutdown procedure via the line SOA_PROTECT. This can also be triggered by a total output stage failure (which passes enough current through R5175 to turn on Q5188) via OVERLOAD or by an excessive DC offset at the output terminals (via R5185) via V_DET. All these signals,

35、 and others, feed into the protection module, described below.The protection module comprises 8 transistors and associated parts positioned at the back of the PCB near the preamplifier output sockets. It has a single output line named PROTECT which, when pulled down from Vcc to ground, instructs the

36、 system P IC151 to shut down the whole amplifier. This occurs when any of the following events happen:1) Any amplifier channel pulls current through the SOA_PROTECT line for long enough to charge up capacitors C5871 and then C5872 so that Q5874 turns on.2) Any amplifier channel pulls current through

37、 the OVERLOAD line for long enough to charge up C5882 and turn on Q5882 and thus Q5884.3) Any amplifier channel has a large long term (DC) offset (typically greater than +/-3V) sFficient to charge up C5861 enough to turn on either Q5862 (positive offset) or Q 5864 (negative offset). These then turn

38、on Q5863. N.B. This circuit is also used to detect imbalances in both the Vcc/Vee and +/-15V power supplies (the latter is generated on the Power Supply board).4) When the PTC thermistor TH585 mounted at the top centre of the heatsink gets sFficiently hot (around 100C) and thus high resistance enoug

39、h to cause Q5855 to turn on via the +12V supply. Intermediate temperatures will not activate PROTECT but will provide signals to the level detec-tors associated with the FAN_1 and FAN_2 lines, to run the cooling fans at high or low speeds respectively.Note that the fans 12V supply is gated via Q5909

40、 and Q5911. This means the fans will not run when no signal is present on the FL, C or SR channels, so that during quiet passages no fan noise should be audible.AVR400 Main Power Supplies Circuit DescriptionThe main DC power supplies are located on the Power Supply Board - a double sided PTH PCB adj

41、acent to the Main Board. Note that the mains input switching, mains fuses, standby power transformer with its associated unregulated DC supply and the relay for enabling the power amplifier supply rails are located on the Main Board. The two boards communicate via CON501.Considering the Main Board f

42、irst, the mains voltage switching uses a double pole double throw slide switch accessible from the back panel. One pole addresses the standby transformer and the other the toroidal power transformer. Ensure the switch setting matches the supply voltage before switching on the AVR400. Nominal setting

43、s are 115 and 230V +/- 15%. The 20mm 115V fuse in line with the toroidal trans-former is rated at 15A T (Time delay) and the 20mm 230V fuse is rated at 8A T. Always replace these fuses with the same type and value. The standby transformer T5941 is not fused but is designed to go open circuit in case

44、 of overheating (e.g. if left connected to a 230V supply for longer than a few minutes when the mains voltage selector is set to 115V). The standby transformer generates approximately +9V DC via the bridge rectifier diodes D5495/6/7/8 and the 1,000F reservoir capacitor C5947.This is sent via pin 7 o

45、f CN501 to the Power Supply PCB (confusingly marked as 5V). The rail voltage is also routed to the system microprocessor (P) via D5965/R5965 and pin 6 of CN103 as POWER_MUTE.The 5V relay RY594 is normally open. When the mains switch is closed then the SUB_POWER rail (approx +4.3V) is activated from

46、the Power Supply PCB via the standby transformer. When the system has booted correctly, without any shutdown signals, then the POWER_RELAY signal from the system P also goes high, pulling down Q5947 hard. Only then does the relay close and switch on the main toroidal power transformer, enabling the

47、rest of the system to boot up.Now consider the Power Supply Board, found on page 14 of the schematic. This generates all the main DC supplies for the AVR400 except +Vcc and -Vee for the power amplifiers and the non-logic part of the VFD display requirements of the Front Panel Board. Note that additi

48、onal local regulation also takes place on the other PCBs, e.g. for large digital ICs.Two secondary windings from the toroidal power transformer are fed in via CN63. Pins 1, 2 and 3 con-nect to a centre-tapped secondary winding used to generate approx +/- 20VDC via the bridge rectifier diodes D603/3/

49、4/5 and the 2,200F 35V reservoir capacitors C609 and C610. R603 and R604 are 0.47R 1W fusible resistors for circuit protection if they fail replace only with the same type and value. The 3 terminal regulators IC63 and IC62 are mounted on two of the larger heatsinks near the back of the amplifier. Th

50、ese provide +/-15V to the op amps on the amplifiers Input Board via the 11-way connector BN62. The Input Board also then routes the +/-15V onwards to the Front Panel Board.Pins 4 and 5 of CN63 receive AC from another transformer secondary to generate approx +15VDC via the heatsink mounted bridge rec