Arcam-C30-pre-sm维修电路原理图.pdf

《Arcam-C30-pre-sm维修电路原理图.pdf》由会员分享，可在线阅读，更多相关《Arcam-C30-pre-sm维修电路原理图.pdf（58页珍藏版）》请在收音机爱好者资料库上搜索。

1、Service Manual C30 Pre-Ampli er Issue 1.0 ARCAMARCAM Bringing music this supply powers the micro and digital circuits. The primary of the Toroid supply transformer Tx2 is connected to CON3 and the power to this is switched on and off by the relay RLY1. The transformer has a number of secondary outpu

2、ts and we use separate taps and bridge rectifiers networks followed by bulk capacitors to smooth the ripple. The voltages generated are +24V and -24V for the main analogue supplies, +46V for the HT supply to the VFD, and +18V, which is used to power the trigger output. The smoothed +/- 24V then goes

3、 through regulators REG 2 and REG 5 to create +/- 18V this is passed the pre-amplifier PCB via CON4. Another set of regulators REG 3 and REG 6 follow taking the 18V and creating a +/-15V supply that is available for add on modules such as the 7.1 channel input board. A 5v supply is derived via regul

4、ator REG 4 from the 18V to run the headphone amplifier. Mains detect. A mains present detector runs from the standby transformer, this detects the loss of mains using a peak hold circuit based around D7/TR1/DZ1 and TR2. If the power is lost this piece of circuitry sends a flag to the microcontroller

5、 so it can mute the outputs and shut down the unit. See Fig 1 for notes on protection modes. 12v trigger and RC5 receiver. The trigger output on SKT2 is driven through TR4 to provide a current limited supply at around 13V. IC1 A and B are used to demodulate incoming RC5 from socket SKT2. IC1A is a b

6、and-pass filter centred on 36KHz. This is followed by a peak detector circuit that demodulates the incoming signal. Fig 1. Protection and mute mode and measurements. Prot line Measured at. Working reading AC present Resistor R12 +4.5v Mute* Con 8 Pin 5 +4.5v Standby* Resistor R5 at point P18 .7v Tri

7、gger ResistorR10 at point P54 +1.8v Pre-amp input card. Introduction. The pre-amp stage is a high-performance, DC coupled design with microprocessor control of input select, two independent tape loops, electronic volume control and tone bypass. It features a discrete power supply and low- noise line

8、ar circuitry to obtain exceptionally low distortion and noise performance results. Power supply stage The secondary transformer output windings from the main toroid transformer are connected to SK300. The A.C voltage is rectified and smoothed by D300, D301, D306, D307 and C300, C301. The unregulated

9、 voltage should be around +/- 27 V obviously this is dependent on the A.C level at the mains inlet socket; F300 and F301 are the secondary A.C s.m fuses these are rated at 2A. The voltage regulators are discrete emitter followers the +15 voltage stage is described below as the 15 v stage is effectiv

10、ely very similar. Q300 and R300 act as a constant current source, supplying around 7mA into D310. C302 and C314 reduce ripple and broadband noise on the zener diode. Q305 and Q306 form a complementary Darlington NPN transistor, which is configured as an emitter follower producing +15v at its output.

11、 C303 is to provide bulk charge storage and to reduce the AC output impedance of the power supply. D302 prevents reverse bias of the supply during power down. Z301 is a conventional LM317 type circuit to regulate the +15v rail down to +5v for the tone and volume control circuits. Input switching Eac

12、h of the inputs has a pair of diodes to the +/- 15v rails to prevent static spikes from causing damage to the CMOS multiplexors. In addition, there is a simple resistor- capacitor filter with a corner frequency of approximately 340kHz to remove any unwanted high frequency interference from the signa

13、l. This uses high quality WIMA polypropylene capacitors for the best possible performance. Z104 (left) and Z105 (right) are the main input multiplexers, which are configured in a “virtual earth” unity gain arrangement with Z115 and Z116. This is an inverting circuit topology and the phase is correct

14、ed by the inverting volume control. Z115B (left) and Z116B (right) are the integrating servos, which remove any D.C coefficient from the Analogue input switching stages before the signal is passed onto the following stages, R180 and C147 (left) form a filter to remove any broadband noise from the se

15、rvo output and to improve the speed response. Z100 Z103 are the Tape output selectors these are non-inverting and the outputs are again buffered by Z9 a/b and Z10 a/b before arriving at the two tape loop outputs. Z106 is configured as a double pole changeover switch and is used to select the tone co

16、ntrols or direct by pass mode. (See below for more information). Tone controls The tone control stage is non-inverting and uses a gyrating bell filter for the Bass and a simple shelving filter for the high frequencies, the left channel only will be described. The input is attenuated by 6dB and biase

17、d to a voltage of +2.5v D.C by C111, R113, R112, R110, R111 and C110. This is so the signals fall within the 0 5v D.C required by the digital potentiometer Z108. Z111B and its associated components form an active equivalent of a series resonant LCR circuit. This has an impedance minimum 5.4k at arou

18、nd 80. The digital pots Z108D and Z108A control the bass and treble respectively, this accomplished by moving the wiper connected to the frequency-sensitive impedance between to non inverting and inverting terminals of Z112A, effectively changing the ratio of feedback boost and feed forward attenuat

19、ion of the circuit at the desired frequencies, thus providing a EQ gain control that is on a logarithmic scale, with the use of a linear pot. Z112B provides the 6dB of gain necessary to bring the nominal level of signal back to unity C116 and C117 remove the 2.5VDC offset from the output to prevent

20、click and bangs when the tone control are activated. Z108 is controlled by a simple 3-wire serial interface from the microprocessor. Each of the digital lines has its own ground return these are terminated at the GND pin of the chip to minimize any electromagnetic interference. Volume control Z107 i

21、s a VSDVC electronic volume control IC. It works in conjunction with external op- amp Z117a/b by varying the feed-forward and feedback resistors in an inverting gain configuration, the volume control is driven by 3-wire data from the H8 micro on the display board if the control receives no data it w

22、ill remain in Audio mute mode. Relay RLY100 shunts the output of the Op- amps to ground at switch on power down and when switching between inputs. Audio output stages. The Audio output stage contains the buffered, un-buffered and balanced outputs as well as the headphone driver. The audio signal fro

23、m the preamp PCB enters the board on CON100 and the direct signal goes straight to the output via the mute relays RlY100A and RLY101B. A buffered version of the signal is created by IC100 and IC101. IC100 and IC101 are op-amps configured as unity gain non-inverting buffers. The C30 also has a Balanc

24、e XLR output stage that drives into the balanced line drivers IC103 and IC104. These line divers create a transformer-less balanced output. Headphone Output. The selected audio output signal is driven into the headphone driver IC102; this signal then passes through CON101 and CON102 to the headphone

25、 socket SKT101. The mute signal passes through the switch contacts in the headphone socket so when headphones are inserted the main outputs are relay muted. Please note: this means that if the headphone sockets control contacts are faulty or damaged the unit will be permanently stuck in audio mute m

26、ode. RC5 remote code assignment change. The C30 has the ability to switch between RC5 system code 16* and 19, we can achieve this by pressing and holding the Phono/Aux CD and AV DVD buttons simultaneously the display will show. RC5 System Code 16* We can toggle the system code using the rotary encod

27、er. Display board The display board is very similar in design to the board that has been used for many years in the A85 family of products inc FMJ A32 and as such those of you familiar with these products will know there way around this board, a full description follows. The power supply rails for t

28、he display board are derived from the main board we should expect to see the below supplies in place (Fig 2.) Fig 2 Display board power supply pins Power supply Pin number of SK1 + 5v D.C (micro) Pin 14 + 5v D.C Pin 1 + 46v D.C for VFD HT Pin 3 Please note: the H8 micro is very critical of the +5v s

29、upply and as such the unit may crash or fail to power up during use if the +5v supply drops below 4.5v. H8 Microprocessor The H8 micro at location Z1 is pre- programmed by Arcam using a flash- programming module and cannot be reprogrammed in the field unless you have access to the appropriate hardwa

30、re and software. The H8 forms the heart of the C30 and takes on all major control functions including. 1. Control of the input switching. 2. Controls the action of the volume cont. 3. Monitors protection status and mute lines A85/A90/A32 only. 4. Sends display information to the VFD. 5. Receives and

31、 decodes RC5 data. 6. Receives data from rear panel remote input. 7. Stores setting information via 24C02 E- prom. At initial power up the H8 micro is reset by Z2 a DS1233 econo reset package. The input switching information is driven out to the Pre-amp card via the 9 select lines that appear on Pin

32、s 14 22 of SK3. The Volume control and tone control circuits are driven from the SDATA SLOAD and SCLK data lines from SK3. The Mute status line has control over the pre-amp output relay at location RLY100; the mute is triggered during power up/down and between input selections and under Mute command

33、s. Within the C30 the DC prot, Therm, VI prot and SP1/SP2 control lines are all connected to Digital ground on the main board of the pre-amp as these are not required within this product. The H8 drives the VFD via 4 Data lines that can be seen on R64 R67 as DISPDAT, DISPCLK, DISPBLK, DISPLAT these d

34、rive directly into the VFD. Remote Data can be received by the C30 via the 3.5 mm Phono jack on the rear of the Pre-amp and the previously described remote demodulator on the main board this demodulated RC5 arrives on the display board via Pin 3 of SK1 and goes into a common IR input pin of the H8 m

35、icro (pin 87) this pin is also used to pick the RC5 code up from the Display onboard remote receiver. At power up the H8 reads all previously stored and last settings used by the amplifier from the e-eprom at location IC5 these will include the last input used and tape settings also tone control and

36、 input level settings, any changes to the set-up of the amplifier are sent to the e-eprom for future recall, at power down the H8 downloads its settings to the e- eprom. All indication LEDs are driven directly from the H8 micro, these LEDs are tagged onto the +5v rail via 10k current limiting resist

37、ors Q1 and Q2 form a toggle between Green and Red for the standby/power LED. The volume control is driven from a Rotary encoder at location SW18 the toggle lines from the encoder arrive at the H8 as control lines Phase A and Phase B on Pins 93 and 94. Multi channel input module (optional) Introducti

38、on The multi input module an optional expansion board that allows the existing Amp/Pre-amp to become part of a surround system when driven by a DVD/SACD player with Analogue surround outputs. The board has two sets of 7.1 input (8 channels) these are labelled as MCH1 and MCH2 and accept Left, Right,

39、 Centre, Left surround, Right surround, Left Back, Right back audio Information. All input channel levels can be trimmed levels to allow for system balancing. Put very simply this is an eight-channel preamplifier. Power supply The board is powered from the +/- 15v supply on the existing pre-amp boar

40、d on board regulators REG100 and REG101 regulate these rails down to 5v and +5v respectively. The digital sections of the circuit are powered by a single +5v rail this is isolated from the main 5v rail via inductor L100. Capacitors C100, C101 and C105, C107 act as bulk charge stores to prevent curre

41、nt surges from affecting the main pre-amp stage power supply stages. Micro Processor The micro controller operates from a 4 Mhz crystal and is in control of all of the boards function via its input/output ports. The micro controller is reset on power up via R/C network R101 and C120. The micro contr

42、oller stays in reset condition for approximately 500ms this allows the host micro controller (H8 Z1 on display board) to initialize and for the power supplies to settle. The Host micro communicates with the onboard micro via CON 101. Three lines are used for communication these are seen on the circu

43、it diagram as PB0, receive from ExpBrd and Transmit to ExpBrd. When the host is communicating with the onboard micro controller PB0 will be driven low, otherwise the Data sent will be ignored. Input switching The input allow for the signal routing of the eight channels from either of the inputs thes

44、e are MCH1 and MCH2, select lines S1-S2-S3 are used to select each bank of inputs this inputs stage utilizes 6 x 74HCT4053 multiplexers you will notice that IC204 and IC205 only utilize the S1 and S2 select channels as this input switch only deals with two channels (Back left and Back right). Please

45、 note: The software will only allow one set of inputs to be selected at any one time. The outputs of the input multiplexers drive into a group of 8 line drive Op-Amps (IC300-IC307) these are configured two pole integrating D.C servo before reaching the Volume control stages. Volume control Volume co

46、ntrol is performed by two channel Burr-Brown PGA2310 volume control chips. The gain is under micro control with steps of 0.5dB. All volume control chips share Data, Clock and Mute control but have Chip select lines that are grouped in the following way Front Right, Front Left, Centre and Sub share t

47、he same select line, and the remaining channels share a chip select line (Surround right and Left, Back right and Left). The volume of each channel can be controlled individually “trimmed”. If a loud clicking is heard on a individual channel whilst adjusting the volume it is probably the input stage

48、 that is at fault and not the volume control chip itself, the input stage should prevent D.C levels form entering the volume control. Output driver stage The output driver stage consists of four OPA2134 dual channel Op-Amps (IC400- IC403) each output for instance Front left channel takes one channel

49、 of the op-amp. The front left and front right channels are driven down into the Pre-amp board via Pins 1 and 2 of connector Con400 and is fed into the input switches of the Pre-amp boards multiplex on Pin 9 from this point the signal is dealt with as a normal signal input into the Pre-amp. Please note: the left and right signals are seen on the L937 pre-amp card circuit diagrams as module left and