Arcam-A80-int-sm维修电路原理图.pdf

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1、DiVAServiceManualA80 AmplifierP80 Power AmplifierIssue 1.0ARCAMARCAMBringing music & movies to lifeBringing music & movies to lifeRadioFans.CN 收音机爱 好者资料库 Contents List ! Circuit description o A80/P80 ! Technical specifications ! Circuit diagrams o L943AY ! Transformers o L916TX 115/230VAC toroidal o

2、 L917TX 100VAC toroidal o L907TX 100VAC frame ! Exploded view diagram o A80 ! Mechanical & packing parts list o A80 o P80 ! Circuit board silk screen o A80 o P80 ! Circuit board parts list o A80/P80 combined RadioFans.CN 收音机爱 好者资料库 Circuit description. Power supply. The mains input to the unit is su

3、pplied at SK200 and is filtered the Y Caps and locations C200 /C201 and X cap at location C209, these are in-place to reduce mains born HF interference and to prevent bridge rectifier noise from leaving the unit. The mains select switch at location SW200 works in conjunction with the dual primaries

4、on the 115/230v transformers, the switch allows for the units to be used in territories running a 115v or 230v grid when the switch is set to the 115v position the primary windings are connected in parallel. Fig 1. Fuse value information. Fuse location. Value. FS200 T2.5A (20mm) FS201 T2.5A (20mm) F

5、S200 (100v) T3.15A (20mm) FS201 (100v) T3.15A (20mm) FS202 (s.m standby 9v a.c rms) T500mA (s.m) FS203 (D.C inline) T2.0A (20mm) FS204 (D.C inline) T2.0A (20mm) The standby Transformer TX200 continuously powers the digital circuitry (+4.8v(D) when power is connected to the unit, this supply powers t

6、he Micro via a regulating circuit based around regulator REG 201 special mention should be made of fuse FS202 as any interruption to this supply will render the unit completely lifeless and as such this circuit should be checked before inspecting any other areas of the board. We will see that the ma

7、in power transformer TX200 supplies a separate secondary winding for the +15 and 15v analogue regulation stages via the two fuses at board locations FS203 and FS204, the failure of either of these fuses will cause the op-amps connected to the regulated rails to swing D.C. The regulator at location R

8、EG 200 regulates the +15 rail and intern supplies the +5V(A) analogue supply via the reference Zener at location DZ200 and drive transistor TR200. The high level power amp A.C supplies arrive at Con204 as a 4-wire supply this allows us to implement a dual bridge network circuit with 4 individually s

9、moothed D.C rails these are labelled as +45(L), +45(R) and -45(L), -45(R) we pull a 38v rail from this point to form the VFD cathode bias voltage via R211 Con205 delivers the 3.3 V A.C supply to the main board and then onto the display VFD via R203 (2R2 f.u). Fig 2. Supply identification and related

10、 components. Supply Related components + 45v L Left power amp positive rail. + 45v R Right power amp positive rail. - 45v L Left power amp negative rail. - 45v R Right power amp negative rail. - 38v VFD Display cathode rail derived from 45v(R) +15v (A) IC 300, 301, 302, 303, 304, 305, 306, 307, 308,

11、 309 also including the input clamp diodes all within the pre-amp stage.- 15v (A) IC 300, 301, 302, 303, 304, 305, 306, 307, 308, 309 also including the input clamp diodes all within the pre-amp stage.+ 5v (A) IC309 volume control +4.8 (D) Input trigger stages, signal detect IC700, delayed off IC703

12、, IC701. Main micro IC600.Remote pickup, Master reset IC601, Over current detect-AC detect thermal cut-out IC600 Fil 1/Fil 2 3.3v filament supply. Pre-amp. The A80 Pre-amp has inputs for Phono, Aux, CD, Tuner, AV, DVD and Tape. All inputs except Phono have a simple resistor-capacitor 340Khz low pass

13、 filter to remove any unwanted high frequency noise from the input signal/local area, a pair of diodes on each input connected to the +15/-15v rails prevent damage to the CMOS input switching chips at locations IC300 and IC301, if any offset is seen at the input the switching chips on a given input

14、we may suspect the failure of one of the input diodes. Fig 3. Logic status of IC302 and 303 (switching chip). Low= 0V High=4.8 (Cmos). Input. A0 (pin 1) A1 (pin 16) A2 (pin 15) Phono Low Low Low Aux Low High Low CD High High Low Tuner Low Low High AV High Low High DVD Low High High Tape High Low Low

15、 The outputs of IC300 (L) and IC301(R) can be seen on pin 8 as a current signal and such this can not be viewed via CRO although a 100 ohm resistor inline with the scope probe may yield some results, from here we drive into line drive op-amp IC307 (L) and IC308 (R) signal can be seen at the output p

16、in (1) and travelling into the volume control chip (IC309) on pins 16 (L) and 9 (R) the output from the Volume control is driven into IC307 at pin 6 (L) and IC308 pin 6 (R) and seen again on pins 7 on both IC307 and IC308. After the Con 302 and Con 303 we drive directly Into the power amp stages but

17、 from this point we can configure the unit as a separate Pre amp/Power amp by moving the jumpers to the pin 2 and 3 of Con 304 and Con 305, and then remove the jumpers at Con 302 and Con 303 this may also be of use when fault finding as we can effectively isolate the and D.C offset/distortion proble

18、ms coming from the Pre amp stage to the power amp stages and test these stages as a separate entity. The Pre amp power up mute and power down mute is controlled by the relay at location RLY300 A/B the relay also triggers to mute the switching noise when switching between inputs (see micro control/pr

19、otection and display section). Power amp stages. The main power amplifiers are of a Class A/B design which use SAP “audio” transistors in a asymmetrical current feedback configuration, Input and feedback paths are D.C coupled and there is a active integrating servo to remove D.C offsets from the out

20、puts. The basic principle of operation is as follows: Left channel description given only, read all references as 5xx for the right channel. The input level of the power amp stage is clamped by the 3V9 zener diodes at positions DZ402 and DZ403 this protects the power amp input stages from gross over

21、load and subsequent damage R410 and R402 and C416 in parallel form a 340khz filter. IC400A is a V-I converter with a gain of 2 its output will be a accurate amplification of its input voltage (i.e the output voltage at pin 1 will be identical to the input at pin 3 but twice the amplitude) the output

22、 voltage is driven unto a 44 ohm load formed by R445 and R446 this op-amp is used in a slightly unusual configuration in that its power supply pins are used as a current output and the output pin is used as a current feedback. Transistors TR404 and TR408 supply the +/- 15v rails and act as cascades

23、to pass its supply pin currents through to the current mirrors. The “feedback current” flows back from the power amp output via R447-R450 to allow IC400A to swing its output, this is why the term current feedback is used its is the current flowing in the feedback resistors that sets the overall gain

24、 of the amplifier. IC400B acts as an inverting integrator and its purpose is to remove DC from the loudspeaker outputs. Any positive D.C offset will cause the output of IC400B to go negative thus increasing the current in its negative supply pin and pulling the output voltage back to zero R420 and C

25、442 set the time constant of the integrator so that audio frequencies are ignored The transistors found at locations TR400 and TR401/TR402 form the PNP Wilson mirrors and TR416 and TR411/TR417 form the Wilson NPN current mirrors, emitter degeneration is provided by R405, R406 (+) and R407, R408 (-).

26、 R415 and R416 decouple the current mirror stages from the main power supply stages to allow the bootstrap circuit to operate this circuit is formed by C423 and C424 and the Metal film 1 watt resistors at locations R452/R453, the boots strap is provided to allow the output stage rails to go up and d

27、own slightly with the output signal to the loudspeaker, this enables the driver stage to fully saturate the output drivers giving the greatest output and the best thermal efficiency. TR405 and TR407 are the Pre-drivers, TR412/TR414 and R411/R434 provide a current limit of about 30mA under fault cond

28、itions. R423 and R428 loosely couple the outputs of the output drivers to the inputs of the SAP output devices, this allows the output devices inbuilt temperature sensing diodes to accurately control the quiescent current of the output drivers as the temperature varies, C425 and C405 ensure that bot

29、h halves of the output stage receive an equal A.C component. The output transistors are TR413 and TR415 these are specially designed for audio power use Sanken SAP15N and SAP15P devices they provide a inbuilt 0W22 thick film power resistor and temperature sensing diodes that track the VBE versus tem

30、perature characteristics of the power transistors allowing for accurate control of the quiescent current. R459 and C427 form the Zobel network which is provided to ensure that the amplifier see a constant and resistive load at high frequencies C421 locally couples the “High frequency” and signal gro

31、unds together at the input stage for the same reason. Any signs of burning or scorching of R459 will indicate that the unit amplifier channel(s) have been running unstable or oscillating. The Bias should be set for minimum distortion (THD+N) using a 0.5v rms 20 Khz sine wave into the CD input with t

32、he amplifier set for full gain, the absolute maximum level of Bias acceptable is 22mV measure across CON401 (L) or CON 501 (R) the adjustment is made using RV400 and RV500 we set the bias at the factory using an extremely accurate Audio Precision-audio analyser. If you do not have access to a distor

33、tion level meter capable of 0.05% or better accuracy you may be able to rough set the amplifier to a typical reading of 15mV (at cold switch on). Fig 4. Suggested blanket replacement parts for power amp failures. Location Description Model Part no. TR413 Output driver + SAP15NY 4CSAP15N TR415 Output

34、 driver - SAP15PY 4CSAP15P TR410 Predriver + FMMT 497 4AFMMT497 TR412 Predriver + ZDT 6758 4AZDT6758 TR414 Predriver - ZDT 758 4AZDT758 TR405 Predriver - FMMT 597 4AFMMT597 TR401 Current mirror PNP BC859B 4A859 TR402 Current mirror PNP FMMT 597 4AFMMT597 TR411 Current mirror NPN FMMT 497 4AFMMT497 T

35、R417 Current mirror NPN BC849B 4A849B TR412 Driver bias + ZDT 6758 4AZDT758 Fig 4a. SAP NY/PY output driver information. SAP 15NY SAP 15PY S-E = 0.22 ohm. Under output driver failure conditions the 0.22 internal emitter resistor will usually go open, the resistor should be measured between pins S an

36、d E. Micro control/protection and display. The micro is tasked with providing an instantaneous safe operating area for both the amplifier and loudspeaker by monitoring the below areas. o D.C at both left and right channel outputs. o Over current within either power amp stage. o Over temp detection f

37、or both power amp stages. o A.C present detection. Please see fig 5. For voltage readings with regards to the protection operations. Within the A80 integrated amplifier these tasks are performed by the H8 type micro at circuit location IC602, within the P80 power amp version the tasks are performed

38、by the PIC micro at location IC603, the protection lines are “daisy chained” to both micros regardless of witch one is fitted. To operate both micros require a constant stable supply voltage, this is derived from the +4.8v(D) rail from transformer TX200 and via regulator REG201 this supply should be

39、 constant at anytime mains appears at the amplifier power input. Please note: This supply is protected from over-current and over-voltage operation by the surface mount fuse at location FS202 T500mA and as such if the Amplifier fails to power up this supply should be checked before making any furthe

40、r investigations. We also need to see a 4.00 Mhz clock at crystal location X600. The micro interfaces with the pre-amp stage input selection (see Fig 3) and the volume control level adjustment we also drive the VFD via the display drive/keyboard scan micro at location IC800. IC602 receives Keyboard

41、scan data and RC5 from the remote pick-up diode at location RX800. The master power on reset can be found on the display board and switches HI (4.8v) after mains in. Fig 5. Working status of protection lines and fault status. Low =0v High = 4.8 (Cmos). LocationFault Line Output pin Working IC 601A A

42、C present 2 High IC 600A Over current 3 Low IC 600B Therm prot (L) 6 High IC 600D Therm prot (R) 11 High IC 600C Therm prot main 8 Low R634 D.C prot (L) N/A Low (D.C) R635 D.C prot (R) N/A Low (D.C) R663 D.C prot combined N/A Low The Protection is live at all times that even in standby due to the fa

43、ct that all chips related with these functions are driven from the 4.8(D) supply rails. As we can see from Fig 4 we can isolate the left and right channel protection lines for both over current and D.C offset by looking at the protection lines before they are mixed into single fault status lines for

44、 the micro at location IC600 this will allow us to identify the channel that is “flagging the fault”. Both versions of the Amplifier have the ability to warn the user and/or engineer of a internal fault, the A80 will use both the Power LED and front panel display, the P80 has no display and as such

45、uses the sequence of LED flash codes listed below in Fig 7. Fig 6. A80 fault alert information. Power LED status Fault indicated LED red during start up DC offset fault Led red during normal use Fault as shown on display Fig 7. P80 fault alert information. Power LED status Fault indicated LED flashi

46、ng green DC offset (left or right) Flashing red Short circuit fault (over current) Flash amber Thermal fault (heatsink L or R) Red on flash green Multiple protection lines triggered The Micro has direct control over all internal relays for protection and output control, the speaker relay control lin

47、es can be seen on the diagram as SPKR1 for SP1 and the SPKR2 for SP2 outputs, these lines switch High to engage the relay. The A80 pre-amp relay should disengage when switching inputs to prevent any chip switching noise from leaving the pre-amp stage the control line can be seen on R385 and switches

48、 High to engage the relay. Signal Detect and Delayed off P80 only. Signal detection is achieved by amplifying the signal present at the power amp inputs by a large amount using two channels of a quad op-amp at location IC700 A/B the outputs of this op-amp are summed by a non-inverting comparator for

49、med using the two remaining op-amp channels these will produce a active High reset pulse at the output pin 14. When mains is plugged into the P80, the master *Reset line goes low and the 0.38Hz clock starts ticking. The *Reset pulse resets the latch effecting a HIGH *Q output and thus a LOW circuit

50、output. When the signal detect Latch and Counter Reset go HIGH (an input is detected), the *SD latch input is driven LOW by the inverter and *Q goes LOW the circuit output then goes high switching the Amplifier on. If the Amplifier does not see audio on its Power amp inputs for either 12 or 45 minut