《Alesis-Midiverb3-sp-sm 电路图 维修手册.pdf》由会员分享，可在线阅读，更多相关《Alesis-Midiverb3-sp-sm 电路图 维修手册.pdf（23页珍藏版）》请在收音机爱好者资料库上搜索。
1、ALESIS MidiVerb 3 (M3) Service Manual P/N: 8-31-0014-A RadioFans.CN 收音机爱 好者资料库 Preface This document is intended to assist the service technician in the operation, maintenance and repair of the Alesis device. Together with the User Reference Manual, this document provides a complete description of t
2、he functionality and serviceability of the Device. Any comments or suggestions you may have pertaining to the document are welcome and encouraged. READ THIS! In addition to any purchase price that Alesis may charge as consideration for Alesis selling or otherwise transferring this service manual (“M
3、anual”) to you, if you are not a service and repair facility (“Service Center”) authorized by Alesis in writing to be an authorized Service Center, Alesis sells or transfers the Manual to you on the following terms and conditions: Only Service Centers authorized by Alesis in writing are authorized t
4、o perform service and repairs covered by an Alesis warranty (if any), and transfer of the Manual to you does not authorize you to be an authorized Service Center. Therefore, if you perform, or if the Manual is used to perform, any service or repairs on any Alesis product or part thereof, any and all
5、 warranties of Alesis as to that product and any service contract with Alesis for that product shall be voided and shall no longer apply for such product, even if your services or repairs were done in accordance with the Manual. All service or repairs done by you or with reference to the Manual shal
6、l be solely your responsibility, and Alesis shall have no liability for any such repairs or service work. All such service or repairs are performed at the sole risk of the person performing the service or repairs. You agree that all such work will be performed in a competent, professional and safe m
7、anner at all times and to indemnify and fully hold Alesis and its successors and assigns harmless in the event of any failure to so perform. Your purchase of the Manual shall be for your own ultimate use and shall not be for purposes of resale or other transfer. As the owner of the copyright to the
8、Manual, Alesis does not give you the right to copy the Manual, and you agree not to copy the Manual without the written authorization of Alesis. Alesis has no obligation to provide to you any correction of, or supplement to, the Manual, or any new or superseding version thereof. Alesis shall have th
9、e right to refuse to sell or otherwise transfer repair parts or materials to you in its sole discretion. You shall not use, sell or otherwise transfer spare or replacement parts supplied by Alesis to you (i) to repair or be used in products manufactured for or by third parties or (ii) to any third p
10、arties for any purpose. You shall not make any warranties or guarantees with respect to the products of Alesis or the use thereof on behalf of Alesis or in your own name. The foregoing describes the entire understanding related to sale or transfer of the Manual to you, and no other terms shall apply
11、 unless in a writing signed by an authorized representative of Alesis. All Trademarks are property of their respective companies. RadioFans.CN 收音机爱 好者资料库 Warnings TO REDUCE THE RISK OF ELECTRIC SHOCK OR FIRE, DO NOT EXPOSE THIS PRODUCT TO WATER OR MOISTURE. The arrowhead symbol on a lightning flash
12、inside a triangle is intended to alert the user to the presence of un-insulated dangerous voltage within the enclosed product which may be of sufficient magnitude to constitute a risk of electric shock to persons. The exclamation point inside a triangle is intended to alert the user to the presence
13、of important operating, maintenance and servicing instructions in the literature which accompanies the product. REPAIR BY ANY PERSON OR ENTITY OTHER THAN AN AUTHORIZED ALESIS SERVICE CENTER WILL VOID THE ALESIS WARRANTY. PROVISION OF THIS MANUAL DOES NOT AUTHORIZE THE RECIPIENT TO COMPETE WITH ANY A
14、LESIS DISTRIBUTOR OR AUTHORIZED REPAIR SERVICE CENTER IN THE PROVISION OF REPAIR SERVICES OR TO BE OR MAKE REPAIRS AS AN AUTHORIZED SERVICE CENTER. ALL REPAIRS DONE BY ANY ENTITY OTHER THAN AN AUTHORIZED ALESIS SERVICE CENTER SHALL BE SOLELY THE RESPONSIBILITY OF THAT ENTITY, AND ALESIS SHALL HAVE N
15、O LIABILITY TO THAT ENTITY OR TO ANY OTHER PARTY FOR ANY REPAIRS BY THAT ENTITY. Regarding the Power Supply Fuse CAUTION: The product under service may employ the use of a replaceable fuse. Danger of fire or electrocution if fuse is incorrectly replaced. Replace with only the same type or equivalent
16、 type recommended by the equipment manufacturer. Regarding the Internal Battery CAUTION: The product under service may employ the use of a internal battery. Danger of explosion if battery is incorrectly replaced. Replace only with the same or equivalent type recommended by the manufacturer. Dispose
17、of used batteries according to the manufacturers instruction. RadioFans.CN 收音机爱 好者资料库 Safety Instructions Carefully read the applicable items of the operating instructions and these safety suggestions before using this product. Use extra care to follow the warnings written on the product itself and
18、in the operating instructions. Keep the operating instructions and safety suggestions for reference in the future. 1.Power Source. The product should only be connected to a power supply which is described either in the operating instructions or in markings on the product. 2.Power Cord Protection. AC
19、 power supply cords should be placed such that no one is likely to step on the cords and such that nothing will be placed on or against them. 3.Periods of Non-use. If the product is not used for any significant period of time, the products AC power supply cord should be unplugged from the AC outlet.
20、 4.Foreign Objects and Liquids. Take care not to allow liquids to spill or objects to fall into any openings of the product. 5.Water or Moisture. The product should not be used near any water or in moisture. 6.Heat. Do not place the product near heat sources such as stoves, heat registers, radiators
21、 or other heat producing equipment. 7.Ventilation. When installing the product, make sure that the product has adequate ventilation. Improperly ventilating the product may cause overheating, which may damage the product. 8.Mounting. The product should only be used with a rack which the manufacturer
22、recommends. The combination of the product and rack should be moved carefully. Quick movements, excessive force or uneven surfaces may overturn the combination which may damage the product and rack combination. 9.Cleaning. The product should only be cleaned as the manufacturer recommends. 10. Servic
23、e. The user should only attempt the limited service or upkeep specifically described in the operating instructions for the user. For any other service required, the product should be taken to an authorized service center as described in the operating instructions. 11. Damage to the Product. Qualifie
24、d service personnel should service the unit in certain situations including without limitation when: a.Liquid has spilled or objects have fallen into the product, b.The product is exposed to water or excessive moisture, c.The AC power supply plug or cord is damaged, d.The product shows an inappropri
25、ate change in performance or does not operate normally, or e.The enclosure of the product has been damaged. 1.0 M3 GENERAL DESCRIPTION The M3, and other digital effects processors, achieve their results by slicing analog signals into segments, and then converting them to a numeric value, correspondi
26、ng to the amplitude of the signal at that particular instant. These values are then mathematically manipulated, and stored at various locations in a memory loop for eventual playback. By varying the placement and amplitude of incoming samples, discrete time delays are achieved. When mixed together,
27、and converted back into analog, these delays simulate the reflections associated with natural reverbs, and delays, as well as non natural effects such as reverse reverbs, and gated reverbs. The added capabilities of an 80C31micro controller allow for user manipulation and storage of algorithm parame
28、ters, as well as effects such as chorus, and flange, that require real-time manipulationof algorithms. Please note that there are several different board revisions, so differences will be noticed from unit to unit. 2.0 POWER SUPPLY The power supply begins with the 9 Volt, A.C., adapter. Input from J
29、7 is R.F filtered (or bypassed in some units) by the large torroid and C68. From there it is split for the +12V, -12V, and +5V rails. The +12V rail consists of a voltage doubler (C69, C73, and 2 diodes), a filter cap (C81) a 7812 regulator (VR1), and filter capacitors (C7, C72, and C80). The -12V ra
30、il is a mirror of the +12V rail, consisting of voltage doubler (C70, C74, and 2 diodes), a filter cap (C83), a 7912 regulator (VR2), and filter capacitors (C6, C40, C71, and C82). The +5V rail consists of a rectifier diode, filter capacitors (C75-C78, and C84), a 7805 regulator (VR3), filter capacit
31、or (C85), and many 0.1uF bypass capacitors. Diagram 1 3.0 ANALOG SIGNAL PATHS The inputs (stereo) from J1 and J2 pass through the small toroids for RF suppression (bypassed in some units), A.C. coupled (C1, C2) and have their impedances fixed at 1M by R2 and R3. While operating the unit monauraly, t
32、he input impedance fixed at 500K (R2, and R3, in parallel). From there, the inputs are buffered by U1, and passed through the input potentiometers. The stereo signal is then sent to a X10 gain stage (U1 etc.) and on to the dry side of the mix potentiometer, as well as summed to mono (Via R21, R22).
33、The summed stereo signal is sent to the anti-aliasing filter consisting of most of U4, and associated resistors and capacitors. There are several important features in the filter to be aware of. The first is the use of the LSTMSB (See section 4.5 for a description) signal from the ASIC. This signal
34、is injected into the signal path at U4 pin 12. A signal diode at U4 pin 10 limits the incoming signal to 5V, preventing damage to the analog switch (U6). The output of U4 pin 8 has a tap running to R46, a 2N4401 transistor, etc., and eventually on to an 8031 input port (U27 pin 13) where it is used
35、to detect the audio threshold level necessary for triggered flange and gated reverb. The input sample and hold circuit consists of 1/3 of the 4053 analog switch (U6B), the input sample cap (C29), a buffer amplifier (U4), and a comparator (U5). Also note the differential amplifier (R44, R52, R53, 2 s
36、ignal diodes, 2 NPN transistors) just prior to the comparator. This diff-amp speeds up the response time of the comparator. The signal beyond this point is purely digital, until the DAC output cycle of the DASP 8. At the appropriate time, the DAC will output the processed left, and right signals. Th
37、is action is coordinated with the two output sample and hold circuits (U6A&C, 2 op amps of U3, C22, C23), so that each receives the correct, separate signal for stereo output. After passing through low pass (anti aliasing) filters (2 op amps of U3, Misc. Resistors & Capacitors), the signals are buff
38、ered (2 op amps of U2), and sent through the output potentiometers. From here, they pass through unity gain amps (2 op amps of U2), through impedance fixing resistors (R5, R10) and R.F. suppression toroids, to the output jacks (J3, J4). 3.1 SUCCESSIVE APPROXIMATION Successive approximation is an emp
39、irical approach to the process of analog to digital conversion. The idea is to divide the process into short, manageablesections. Each significant binary weight (starting with the Most Significant Bit) is taken in turn, thus requiring only 16 comparisons to achieve a final value. The process begins
40、with the input sample and hold circuit. 1/3 of the 4053 (U6B) is turned on, allowing the input sample capacitor (C44) to charge or discharge to the level of the current input signal. When the switch is turned off, the capacitor will hold that level indefinitely barring internal leakage . At this poi
41、nt, the SAR (Successive Approximation Register-part of the DASP 8 ASIC) will take over. Starting with the MSB, the SAR will set the bit, and compare the output of the DAC, to the level of the input sample capacitor (via comparator U5). The results of the comparison are stored in the register, and th
42、e next most significant bit is Diagram 2 Diagram 3 compared. This process continues until a value is found for all 16 bits, and the data is ready for further processing by the ASIC. In order to see these signals properly on the scope, it will be necessary to use an external scope sync (use U6, pin 9
43、 as the sync source). Diagrams 2, and 3, show the DAC output during a single SAR cycle, with no input, and full input. 4.0 DIGITAL SIGNAL PATHS The digital portion of the M3 is somewhat complex, incorporating 2 data and address busses, as well as the control circuitry necessary for intercommunicatio
44、n. 4.1 80C31 MICRO CONTROLLER CIRCUIT The 80C31 MPU controls all user interface functions of the M3. These functions range from handling the front panel buttons, to continuously updating algorithm information to the DASP 8 ASIC. Note that the 8031 data buss serves a dual purpose. This buss multiplex
45、es between low order addresses (1st 8 bits), and data. Latch U26 is used to hold the low order address half, during 8031 read and write cycles. The EPROM (U25) is used to hold both program information, and algorithm data. The E2PROM (U24) holds system variables, as well as user preset data. MIDI I/O
46、 is handled through the 8031s built in RXD (Read Serial Data), and TXD (Transmit Serial Data) ports. Front panel keypad decoding is handled through a combination of memory mapped I/O (see section 4.3), and the 8031s built in I/O ports. 4.2 RESET The 8031 reset circuit is perhaps the single most impo
47、rtant circuit in the M3. When this circuit is functioning incorrectly, a complete lock-up of the machine, will occur. A thorough knowledge of the operation of this circuit will greatly facilitate troubleshooting this unit. Note that the first units released did not incorporate the full reset circuit
48、 described below. These units used a simple resistor/capacitor circuit, and would occasionally fail to reset (particularly if the unit was turned off, and then back on rapidly). Most of these early units have been retrofitted with an extra board containing the newer reset circuit. The newest board r
49、evisions incorporate the reset on the board. On power up, the 2N4401 transistor is off (the raw supply hasnt raised up far enough yet to bias the transistor on, through R202, R203, and the zener divider network). C100 is allowed to charge to +5V via R201 and the 1N914 signal diode. When the raw supply reaches approximately 7 volts, the transistor will turn on, discharging C100 through R200, and dropping the reset line low. 4.3 MEMORY MAPPED I/O The M3 utilizes a memory mapped I/O system in order to deal with the wide variety of functions that the 8031 needs
免费区 
