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Alesis MidiVerb IV Service Manuali03/05/99AlesisMIDIVERB IV STEREO EFFECTS PROCESSORService Manual V 1.006/13/95RadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manualii03/05/99PREFACEThis document is intended to assist the service technician in the operation, maintenance and repair of theMidiVerb IV Stereo Effects Processor. Together with the MidiVerb 4 Reference Manual, this documentprovides a complete description of the functionality and serviceability of the Midiverb IV. Any commentsor 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 Alesisselling or otherwise transferring this service manual (“Manual”) to you, if you are not aservice and repair facility (“Service Center”) authorized by Alesis in writing to be anauthorized Service Center, Alesis sells or transfers the Manual to you on the followingterms and conditions:Only Service Centers authorized by Alesis in writing are authorized to perform serviceand repairs covered by an Alesis warranty (if any), and transfer of the Manual to youdoes 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 productor part thereof, any and all warranties of Alesis as to that product and any servicecontract with Alesis for that product shall be voided and shall no longer apply forsuch product, even if your services or repairs were done in accordance with theManual.All service or repairs done by you or with reference to the Manual shall be solely yourresponsibility, and Alesis shall have no liability for any such repairs or service work. Allsuch service or repairs are performed at the sole risk of the person performingthe service or repairs. You agree that all such work will be performed in a competent,professional and safe manner at all times and to indemnify and fully hold Alesis and itssuccessors 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 forpurposes of resale or other transfer.As the owner of the copyright to the Manual, Alesis does not give you the right to copythe Manual, and you agree not to copy the Manual without the written authorization ofAlesis. 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 the right to refuse to sell or otherwise transfer repair parts or materialsto you in its sole discretion. You shall not use, sell or otherwise transfer spare orreplacement parts supplied by Alesis to you (i) to repair or be used in productsmanufactured for or by third parties or (ii) to any third parties for any purpose.You shall not make any warranties or guarantees with respect to the products of Alesisor the use thereof on behalf of Alesis or in your own name.The foregoing describes the entire understanding related to saleRadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manualiii03/05/99WARNINGSTO REDUCE THE RISK OF ELECTRIC SHOCK OR FIRE, DO NOT EXPOSE THISPRODUCT TO WATER OR MOISTURE.CAUTIONRISK OF ELECTRIC SHOCKDO NOT OPENThe arrowhead symbol on a lightning flash inside a triangle is intended to alert the user tothe presence of un-insulated dangerous voltage within the enclosed product which maybe 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 ofimportant operating, maintenance and servicing instructions in the literature whichaccompanies the product.CAUTIONDanger of explosion if battery is incorrectly replaced.Replace only with the same type or equivalent typerecommended by the equipment manufacturer.Battery Manufacturer: Panasonic/MatsushitaType: BR2325Rating 3V, 5mAREPAIR BY ANY PERSON OR ENTITY OTHER THAN AN AUTHORIZED ALESIS SERVICECENTER WILL VOID THE ALESIS WARRANTY.PROVISION OF THIS MANUAL DOES NOT AUTHORIZE THE RECIPIENT TO COMPETEWITH ANY ALESIS DISTRIBUTOR OR AUTHORIZED REPAIR SERVICE CENTER IN THEPROVISION OF REPAIR SERVICES OR TO BE OR MAKE REPAIRS AS AN AUTHORIZEDSERVICE CENTER.ALL REPAIRS DONE BY ANY ENTITY OTHER THAN AN AUTHORIZED ALESIS SERVICECENTER SHALL BE SOLELY THE RESPONSIBILITY OF THAT ENTITY, AND ALESISSHALL HAVE NO LIABILITY TO THAT ENTITY OR TO ANY OTHER PARTY FOR ANYREPAIRS BY THAT ENTITY.RadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manualiv03/05/99SAFETY SUGGESTIONSCarefully read the applicable items of the operating instructions and these safety suggestions before usingthis product. Use extra care to follow the warnings written on the product itself and in the operatinginstructions. 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 operatinginstructions or in markings on the product.2. Power Cord Protection. AC power supply cords should be placed such that no one is likely to step on the cords and suchthat 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 cordshould be unplugged from the AC outlet.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 or other heat producingequipment.7.Ventilation. When installing the product, make sure that the product has adequate ventilation. Improperly ventilating theproduct may cause overheating, which may damage the product.8. Mounting. The product should only be used with a rack which the manufacturer recommends. The combination of theproduct and rack should be moved carefully. Quick movements, excessive force or uneven surfaces may overturn thecombination which may damage the product and rack combination.9. Cleaning. The product should only be cleaned as the manufacturer recommends.10. Service. The user should only attempt the limited service or upkeep specifically described in the operating instructionsfor the user. For any other service required, the product should be taken to an authorized service center as described inthe operating instructions.11. Damage to the Product. Qualified service personnel should service the unit in certain situations including withoutlimitation 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 inappropriate change in performance or does not operate normally, ore. The enclosure of the product has been damaged.RadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manualv03/05/99General TroubleshootingWhile this manual assumes that the reader has a fundamental understanding of electronics andbasic troubleshooting techniques, a review of some of the techniques used by our staff may help.1. Visual Inspection - A short visual inspection of the unit under test will often yield results without theneed of complex signal analysis (burnt, or loose components are a dead giveaway).2. Self Test - Alesis products that utilize microprocessor control contain built in test software whichexercises many of the units primary circuit functions. Self test should always be done following anyrepair to ensure basic functionality.3. Environmental Testing - Applying heat and cold (heat gun/freeze spray) will often reveal thermallyintermittent components (Clock crystals, I.C.s, and capacitors are particularly prone to this type offailure).4. Burn in Testing - Leaving a unit running overnight often reveals intermittent failures such ascapacitors that begin to leak excess current after a significant amount of time.5. Cable Checks - Wiggling cables can reveal intermittent failures such as loose cables or poorly solderedheaders. Remember to check power supply cables as well.6. Flexing the PC Board - Poor solder joints and broken traces can often be found by pressing the PCBoard in various places.7. Tapping Components - Sometimes tapping on a component (particularly crystals) will cause it to fail.8. Power Down/up - Turning the unit off and back on rapidly several times may reveal odd reset and/orpower supply failures.9. Reset Threshold - A Variac (variable transformer) can be used to check reset threshold levels. This canbe particularly useful in helping customers with low line problems.10. Compressors - Using a compressor/limiter is often helpful when attempting to solve low level noiseproblems, as well as assisting with DAC adjustments.11. Sweep Tests - Sweep generators are very useful in checking the frequency response envelopes of anti-aliasing filters.12. Piggybacking - Piggybacking I.C.s is particularly useful when troubleshooting large sections of logic.This is especially true when working with older units.RadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manualvi03/05/99Table Of ContentsPREFACE.iiREAD THIS!.iiWARNINGS.iiiSAFETY SUGGESTIONS .ivGeneral Troubleshooting.v1.00 General Description.12.00 Power Supply.12.10 Battery Backup .13.00 Analog Signal Paths .13.10 Input.13.20 Output.24.00 A-D/D-A .24.10 A-D .24.20 D-A .25.00 Digital Signal Paths.35.10 RESET.35.20 M4 ASIC .36.00 The Front Panel.56.10 The Keypad .56.20 Display LEDs.56.30 Disassembly .57.00 Test Procedures .77.10 Self Test .77.20 Further Testing. .78.00 Troubleshooting.89.00 Schematics.910.00 Software History .1311.00 MIDI Implementation.15OVERVIEW .15THE CHANNEL BYTE.15THE OPCODE BYTE.15SYSTEM INFO DATA.16PROGRAM TABLE DATA.17EDIT BUFFER DATA.17ALL USER PROGRAMS DATA.17SINGLE PROGRAM DATA .17STORE PROGRAM DATA.17NOTES .1712.00 Service Parts List.1813.00 Service Manual History.20INDEX.21RadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manual103/05/991.00 General DescriptionThe MidiVerb IV is a continuation of the Alesis line of quality studio signal processors. Asis the tradition at Alesis, much of units complex functions are incorporated into an LSI ASIC,reducing parts count and cost, as well as increasing reliability and serviceability. The MidiVerbIV pushes the concept of integration further than any previous processors, adding hardware tothe ASIC that was previously discreet components.2.00 Power SupplyThe M4 power supply begins with the 9 Volt A.C. adapter (Alesis P3 type). Input from J8is R.F. filtered by C35 before on/off switch SW1. From there it is split for the +12V, -12V, and+5V rails. The +12V rail consists of a voltage doubler (C11, C18, and D3, D5), a 7812 regulator,and a filter capacitor (C16). The -12V rail is a mirror of the +12V rail, consisting of voltagedoubler (C12, C19, and D4, D6), a 7912 regulator, and a filter capacitor (C20). The +5V railconsists of a rectifier diode (D2), an input filter capacitor (C5), a 7805 regulator, an output filtercapacitor (C10) and a multitude of 0.1F bypass capacitors. Note that the raw +5V line used bythe microprocessor reset, and the SRAM power supply, and is located at the input to the 7805regulator. Likewise, the +12 V and -12V raw supply lines are available for use by the LCD.2.10 Battery BackupBattery backup is actually more complicated than it might first appear, as itdepends on a good system reset (see section 5.10 for details) in order to function properly. Theactual backup circuit consists of a battery (3V Lithium), a 10K resistor (R21) for checkingstandby current (see below), a steering diode (D8), a filter capacitor (C32), and atransistor/resistor/diode combination that acts as a steering diode, while maintaining a highenough supply voltage to prevent SRAM data corruption.SRAM standby current should always be checked. While the unit is off, check the voltageacross R21. If the voltage is higher than 80mV (specification, although a 1 to 20mV range ismore normal) then a problem exists. Usually it indicates a bad (or simply wrong) SRAM, or ashort, somewhere along the SRAM Vcc line.WARNING: Danger of explosion exists if the battery is incorrectly replaced. Replace only withthe same type or equivalent type recommended by the manufacturer.Battery Manufacturer: Panasonic/MatsushitaType: BR2325Rating: 3V, 5mA3.00 Analog Signal Paths3.10 InputThe signal(s) from input jacks J3 (right) and J4 (left/mono) are current limited by R20,R26, and have their impedances set at 1M (stereo), 500K (mono) by resistors R12 and R27.These signals are then buffered by U8C and U8D respectively, before being sent to the inputDigPots (U6B, U6A) via A.C. coupling capacitors C4 and C2. After a small gain stage (U8B,U8A) the signals are passed along to the ADC for further processing.RadioFans.CN 收音机爱 好者资料库Alesis MidiVerb IV Service Manual203/05/993.20 OutputThe differential outputs of the DAC (U12) are converted to a single ended mode via U7Band U7A and their surrounding circuitry. This circuitry also provides some low pass filtering.These signals are then A.C. coupled by C1 and C3 before being sent to the output DigPots.The output of the DigPots is buffered by U7D and U7C before being sent to the output jacks (J1and J2). The output impedance of the unit is fixed at approximately 220 by resistors R15 andR19. C24 and C26 provide R.F. filtering for the outputs.4.00 A-D/D-A4.10 A-DThe A to D is a 128 times over sampling Philips 7360 high performance device. It is astereo part utilizing high Sigma-Delta conversion techniques that eliminates the need for sampleand holds, and extensive anti aliasing filters.The right channel is input through R37, while R47 is a feedback for to the A to Dsinternal input buffer amplifier. R42 and R60 provide negative and positive inputs to the A to Dsinternal sigma delta modulator. C40 is a small filter cap placed between these inputs.The left input is identical and uses R38, R49, R43, R38 and C41.C8, C42, C9, and C43 are the bypass filters for the internal voltage reference. C35 alongwith R34 and R35 act as filters for the negative and positive internal DAC reference inputs.Analog power is supplied through current limiters (R52, and R56) which help suppress currentspikes. C44, C45, and C13 act as bypass filters for the analog supply. The digital supply isfiltered by C16, C50, and R60.R48 is a current reference and has a tolerance of 1% for precision.The A to Ds stereo output is transmitted from the FROMADC line to the M4 ASIC chip(U9).4.20 D-AThe digital to analog converter is U12 which is an AKM 4318A DAC. Like the A to D, thisD to A is a high performance over sampling stereo device. It can achieve an outstanding signalto noise ratio of 98 dB which is unprecedented in its price range. Also, the over sampling naturesignificantly reduces output filter requirements.The analog power filter consists of C16, and C48, while the