Lexicon MPX G2 Service Manual
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Lexicon MPX G2 Service Manual

Guitar effects processor
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  • Page 1 MPX G2 Guitar Effects Processor Service Manual...
  • Page 2 Copyright © 1999 - 2001 Lexicon, Inc. All Rights Reserved Lexicon Inc. ● 3 Oak Park ● Bedford, MA 01730-1441 ● Tel (781) 280-0300 ● Customer Service Fax (781) 280-0499 Lexicon Part # 070-14395 Rev 0 Printed in the United States of America...
  • Page 3 Lexicon Safety Suggestions basement, near a swimming pool, near an open window, etc. Object and liquid entry Do not allow objects to Read Instructions Read all safety and operating fall or liquids to be spilled into the enclosure instructions before operating the unit.
  • Page 4 The following general safety precautions must be observed during all phases of operation, service and repair of this instrument. Failure to comply with these precautions or with specific warnings elsewhere in these instructions violates safety standards of design manufacture and intended use of the instrument. Lexicon assumes no liability for the customer’s failure to comply with these requirements. GROUND THE INSTRUMENT...

  • Page 5: Table Of Contents

    Test Equipment............................ 1-1 Chapter 2 General Information ..............2-1 Periodic Maintenance ..........................2-1 Ordering Parts ............................2-1 Returning Units to Lexicon for Service ....................2-1 Chapter 3 Specifications................3-1 Chapter 4 Performance Verification............4-1 Diagnostics .............................. 4-1 Analog Audio Performance:........................4-1 Setup:..............................
  • Page 6 MPX G2 Service Manual Power Supply: ............................5-27 Battery Voltage:............................5-28 Systems Clocks:.............................5-29 APPENDIX A: Software Error Messages ....................5-29 Chapter 6 Theory of Operation ..............6-1 Analog ..............................6-1 Overview...............................6-1 Input..............................6-2 Tone Block............................6-3 Dynamic Gain ............................6-3 Send ..............................6-4 Aux Inputs (including Speaker Simulator).....................6-5 Output ..............................6-6...

  • Page 7: Chapter 1 Reference Documents, Required Equipment

    Lexicon Chapter 1 Refe r ence Documents, Required Equipment Reference Documents MPX G2 Owner's Manual - Lexicon P/N 070-11542 latest revision Required Equipment Tools The following is a minimum suggested technician's tool kit required for performing disassembly, assembly and repairs: •...

  • Page 9: Chapter 2 General Information

    Return Authorization from Lexicon. If Lexicon recommends that a MPX G2 be returned for repair and you choose to return the unit to Lexicon for service, Lexicon assumes no responsibility for the unit in shipment from the customer to the factory, whether the unit is in or out of warranty.

  • Page 11: Chapter 3 Specifications

    -97dB (unweighted) typical instrument to main outputs in Bypass Sample rate: 44.1kHz Return Mix: When the Return Mix option is selected, MPX G2 will mix the analog Aux inputs with the post converter output signal from the DSP. Throughput delay without send/return loop: Input to Main Output <3ms, nominal...

  • Page 13: Chapter 4 Performance Verification

    Analog Audio Performance: NOTE: In order to properly test the MPX G2, every step in the Setup section must be set in order. This is to insure proper troubleshooting of an MPX G2 if service is needed. Failure to set the unit up properly will cause incorrect readings.
  • Page 14 The range values will be listed as Upper limit values first and Lower limit values. Note: In the tests to follow, Input refers to the Rear Guitar Input Jack on the back of the MPX G2. 32. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Rear Guitar Input jack.

  • Page 15: Input To Send

    The following tests will be testing the Input to Send path as seen in the diagram below: Input To Send Tests In Bypass: This test will verify the Audio signal path from the Rear Input to the Send output of the MPX G2 In Bypass Signal Levels: 1.
  • Page 16 Input To Send Test With Tone On: This test will verify the Audio signal path from the Rear Input to the Send output of the MPX G2 With the Tone circuit enabled. There are 3 parameters that must be set for this test.
  • Page 17 Lexicon 5. Set the Analyzer back to measure level. Signal To Noise Ratio: 1. Apply a 1kHz-sinewave signal at +2.2dBu (1.0 Vrms). 2. Set the Analyzer for a 0dB reference (@ 1kHz). 3. Turn off the oscillator. 4. Verify an output level reading between -99.94 to-120.00 dBu (7.8 to 0.8 uVRMS).
  • Page 18 MPX G2 Service Manual 9. Set the Low Gain to 0, then set the Mid Gain to -25 using the front panel knob. 10. Verify the output level readings for each of the frequency settings in the table below. Freq.
  • Page 19 16. Set High Gain setting back to 0. Input To Send Test With DSP On: This test will verify the Audio signal path from the Rear Input to the Send output of the MPX G2 With the DSP circuit enabled.
  • Page 20 Input To Send Test with Dynamic Gain On: This test will verify the Audio signal path from the Rear Input to the Send output of the MPX G2 with the Dynamic Gain circuit enabled. You will now need to set the following parameters for the following...
  • Page 21 Note: In the following part of this test an oscillator with a tone burst function must be set for the specs below in step 18. The resulting output from the MPX G2 must be feed to a storage oscilloscope that is capable of measuring and storing the information in time domain as indicated in the 2 graphs below.
  • Page 22 MPX G2 Service Manual Feel Good Circuit On 21. Press the Yes button 8 times. The display reads: Devel FGood In 1. Turn the knob CCW so the setting is Out 0 this will disengage the Feel Good circuit. 22. Again apply a 1kHz-sinewave signal Burst at -6dBu (388 mVRMS).
  • Page 23 Lexicon Feel Good Circuit Off Frequency Response Measurements: 1. Press the No button 9 times. The display will read Devel LoCut 0. Turn the knob CW so the setting is 2. Apply a 1kHz-sinewave signal at -20.5dBu (73 mVRMS). 3. Set the Analyzer for a 0dB reference (@ 1kHz). Verify the output level readings for each of the frequency settings in the table below.
  • Page 24 MPX G2 Service Manual 4. Turn the knob CCW to set LoCut back to 0. 5. Press the Yes button 3 times. The display will read Devel HiCut. Turn the knob CW so the setting is 35. 6. Verify the output level readings for each of the frequency settings in the table below.
  • Page 25 Lexicon 11. Verify the output level readings for each of the frequency settings in the table below. Freq. Upper Lower Hz (Vrms) dBu (Vrms) 20,000 (.05) -24.44 (.03) -28.56 16,000 (.05) -23.55 (.03) -27.67 12,000 (.06) -22.09 (.04) -26.21 10,000 (.07) -20.98 (.04)
  • Page 26 Input To Send Tests With Clean On: These tests will verify the Audio signal path from the Rear Input to the Send output of the MPX G2 with the Clean circuit enabled. The following tests parameters will be needed in order to perform these tests.
  • Page 27 Lexicon Signal Level: 1. Apply a 1kHz-sinewave signal at +1.0dBu (870 mVRMS). 2. Set the Analyzer for a 0dB reference. 3. Verify an output level reading between 17.36 to 16.24 dBu (5.72 to 5.0 Vrms). Frequency Response Measurements: 1. Disable all Filters on the Distortion Analyzer.

  • Page 28: Insert Return Inputs To Outputs

    10. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Left Insert Return jack. 11. Connect an audio output cable from the Left Main 1/4 Output jack on the rear of the MPX G2 to the Distortion Analyzer.
  • Page 29 1. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Left Insert Return jack. 2. Connect an audio output cable from the Left Main ¼” Output jack on the rear of the MPX G2 to the Distortion Analyzer.
  • Page 30 2. Press the No button 2 times. The display reads: Devel Split Off. Turn the knob CW to On this will enable the Split switch. Note: The MPX G2 is already set for the proper input level from the last test.
  • Page 31 9. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Left Insert Return jack. 10. Connect an audio output cable from the Left Main 1/4 Output jack on the rear of the MPX G2 to the Distortion Analyzer.
  • Page 32 6. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Left Insert Return jack. 7. Connect an audio output cable from the Left Main 1/4 Output jack on the rear of the MPX G2 to the Distortion Analyzer.
  • Page 33 3.47 6. Set the Analyzer back to measure level. 7. At this time, in order to continue you will want to turn the Soft Sat back 0ff and reset the MPX G2 as described at the top of this test.
  • Page 34 9. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Left Insert Return jack. 10. Connect an audio output cable from the Left Main 1/4 Output jack on the rear of the MPX G2 to the Distortion Analyzer.
  • Page 35 Lexicon 3. Apply a 1kHz-sinewave signal at -17dBu (109 mVRMS). 4. Set the Analyzer for a 0dB reference. 5. Verify the output level reading is between at the following frequency settings. Freq. Upper Lower Hz (Vrms) dBu (Vrms) 20,000 (.030) -28.47 (.020)
  • Page 36 MPX G2 Service Manual 5. Verify the output level reading is between at the following frequency settings. Freq. Upper Lower Hz (Vrms) dBu (Vrms) 20,000 (.50) -63.86 (.30) -67.98 16,000 (.001) -57.63 (.60) -61.75 12,000 (.003) -47.49 (.002) -51.61 10,000 (.007) -40.65 (.004)
  • Page 37 Lexicon 5. Verify the output level reading is between at the following frequency settings. Freq. Upper Lower Hz (Vrms) dBu (Vrms) 20,000 (.002) -52.82 (.001) -56.94 16,000 (.004) -45.07 (.003) -49.19 12,000 (.015) -34.44 (.009) -38.56 10,000 (.030) -27.34 (.020) -31.46...
  • Page 38 Setup: 1. On the front panel of the MPX G2 set the Low, Mid, and High Gain pots to 0. 2. Press the System button until the display reads: System Select Development. 3. Press the Yes button once. The display reads: Devel Split. Verify that it is set to Off 0.
  • Page 39 16. Connect an audio input cable between the Low Distortion Oscillator and the MPX G2 Rear Guitar Input jack. 17. Connect an audio output cable from the Left Main 1/4 Output jack on the rear of the MPX G2 to the Distortion Analyzer.
  • Page 40 MPX G2 Service Manual 6. Set the Analyzer back to measure level. Signal To Noise Ratio: 1. Apply a 1kHz-sinewave signal at +1.75dBu (.95Vrms). 2. Set the Analyzer for a 0dB reference (@ 1kHz). 3. Turn off the oscillator. 4. Verify an output level reading between -92.94 to-120.00 dBu (18.0 to 0.8 uVRMS).
  • Page 41 Midi circuitry can be found in the Troubleshooting section of this manual. 1. Connect one end of a Midi cable to the MPX G2 Midi Out jack and the other end to the MPX G2 Remote/In jack.
  • Page 42 (pedal fully up) to maximum (pedal fully down) within 5 seconds after the test is executed. Otherwise, the test will fail. 1. Connect the footpedal to the MPX G2 rear panel Foot Pedal jack and place the pedal in the up position. 2. Press and hold the Edit button while powering up the MPX G2.
  • Page 43 3. Set the Output Level Pot fully CCW. 4. Set the Input Level Pot fully CW. 5. Power up the MPX G2. Turn the front panel knob to select and load Program # 219 Stand Alone Only InfiniteEcho. Verify Clean Audio Program #219 involves all the effects available in the MPX G2;...
  • Page 44 9. Set the Output Level Pot fully CCW. Shock Test 1. Lift one corner of the MPX G2 four inches off the work surface and drop. 2. Verify that no audio or display intermittence is caused by this action. 3. Repeat for each of the remaining three corners of the unit.

  • Page 45: Lexicon Audio Precision Ate Summary

    This chart represents a summary of test Audio Precision test settings and parameters used by Lexicon Manufacturing in production testing of all MPX G2 product. This is provided as a reference and supplement to bench test settings found in the proof of performance in this manual.
  • Page 46 MPX G2 Service Manual DYNAMIC GAIN ON Input to Send Output Dynamic NONE -5dBu UNBAL FLOAT dBu LEVEL 10.7 11.76 9.64 100K 22-22K Gain -5dBu In Input to Send Output Dynamic NONE -70dBu UNBAL FLOAT dBu LEVEL 3.34 100K 22-22K...
  • Page 47 Lexicon SUM SW ON R. Insert Return to Outputs - NONE -10dBu -10dBu 997 UNBAL FLOAT dBu LEVEL 27.06 24.94 100K 22-22K 10dBu In Sum Switch On SPLIT SW ON R. Insert Return to Outputs - NONE -10dBu -10dBu 997...
  • Page 48 MPX G2 Service Manual Input To Outputs POST DSP Test Description Sweep Left Right Freq. Bal/Unba Gnd/Flt Level Measur Reading Upper Lower Filter Imp. Band Input to Output Level Post DSP NONE +1dBu UNBAL FLOAT dBu LEVEL 26.2 27.26 25.14...

  • Page 49: Chapter 5 Troubleshooting

    SRAM for future analysis. More information on the error log file will follow in this chapter. At this time, due to the failure, the MPX G2 will stop executing the Power On Diagnostics.

  • Page 50: Test Descriptions

    U85 pin 55 will go high causing RESET1/ signal to go high allowing the Z80 (U90) to boot. In the event of a failure, the CPU will not be able to display any messages. The MPX G2 will not function and service will be needed.
  • Page 51 Before the test is executed, a 4 is displayed in the rightmost 7-segment display on the MPX G2. If a failure occurs, an E is then displayed in the leftmost 7-segment display along with the 4 on the MPX G2, indicating an Error E 4 has occurred.
  • Page 52 DSP counts the samples the range must be between (22663 and 22687ns) Before the test is executed, a 7 is displayed in the rightmost 7-segment display on the MPX G2. If a failure occurs, E is then displayed in the leftmost 7-segment display along with the 7, indicating an Error E 7 has occurred.

  • Page 53: Functional Tests / Extended Diagnostics

    These diagnostics are provided to verify specific MPX G2 functions. To enter the Functional Tests / Extended Diagnostics, power on the unit while pressing down and holding down the Edit button. When the display reads Lexicon release the edit button. After 5 seconds the display reads: Diags: Tests <...

  • Page 54: Functional Test Descriptions

    *A Lexicon Dual Momentary Footswitch (Lexicon P/N 750-09277) is connected to the ¼" phone jack on the rear panel of the MPX G2 labeled "Footswitch". The left footswitch is labeled "RING and right is labeled "TIP". A ¼” Phone Plug is used for testing the Insert Return Jacks.
  • Page 55 Foot SW 2 Tip Released Insert Return Jacks: Insert a ¼” Phone Plug to the Left Insert Return Jack on the back of the MPX G2, the display reads: Left Insert Inserted When the ¼” Phone Plug is removed from the Left Insert Return Jack, the display reads:...

  • Page 56: Front Panel Pots

    Front Panel Pots This test verifies the functionality of the Low, Mid, High and Output pots on the Front Panel of the MPX G2. They are connected to Digipots (digitally read potentiometers) on the main board. Therefore, they are read digitally.

  • Page 57: Led Test

    Lexicon When the pot labeled Low gets initially turned CCW, the display reads: Low Pot: Turn CCW: 62* * 62 indicates the position of the pot under test and this value can range from 0-63. Turn the pot fully-CCW and the display will then read:...

  • Page 58: Display Block Test

    MPX G2 Service Manual At the Functions Tests menu turn the Encoder until the display reads the following: Diag: Tests < Display Char Next press the STORE button and release, the display will read the following: Disp Char CW/CCW Hold < to exit...

  • Page 59: Auto Test Execution

    Diag: Tests < Display Block Auto Test Execution Note: This test is for Lexicon Manufacturing use only. The test requires custom test fixtures, which are not available for sale. The following tests are included in the Auto Execution Test: Footpedal Test (refer to this test later on in this chapter)

  • Page 60: Footpedal Test

    < Burn-in Loop Footpedal Test This test can be performed with the customer built Lexicon Foot Controller Test Fixture (Lexicon part #770-08508 - not available for sale) or generic foot controller with a potentiometer value from 10K-500K The test checks out part of LM393 (U8) and its associated circuit as well as the FPGA (U84).

  • Page 61: Midi Test

    > MIDI Test Note: This test is for Lexicon manufacturing use only. The test requires custom test fixtures, which are not available for sale. UUT = Unit Under Test This test verifies that the MIDI input and MIDI outputs (2) circuits are working. The test transmits data out of the MIDI OUT and Remote/In jacks and will attempt to read the data through the MIDI IN jack.

  • Page 62: Dram Test

    MPX G2 Service Manual If the test failed because the MIDI Input didn't received any data, the display reads: MIDI Test Failed Rec Tim (done) If the test failed because the MIDI Output didn't transmit any data, the display reads:...

  • Page 63: Wcs Test

    Lexicon The NO< button is active to exit the Test Menu into the Top Level Menu. WCS Test This test will verify the Writeable Control Store of the Lexichip 2 (U85) is working. The WCS is first filled with the value 55 hex (0101 0101 binary), then each memory location is read to see if it contains 55. If 55 is in the memory location, the location is filled with AA hex (1010 1010 binary), and the next location is processed.

  • Page 64: Rom Test

    MPX G2 Service Manual The NO< button is active to exit the Test Menu into the Top Level Menu. ROM Test This test will verify the ROM’s Checksum, which is a byte size value, is located in the last location of Bank 0.

  • Page 65: Exit Diags

    Diags: Top Level Exit Diags > Pressing the STORE button at this time will exit the diagnostic mode and put the MPX G2 into normal operating mode. Scope Loops The Scope Loops are tools that will help the technician troubleshoot a problem.

  • Page 66: Clear Err Log

    MPX G2 Service Manual At the Top Level Tests menu, turn the Encoder until the display reads the following: Diags: Top Level SoftwareErrLog > To view the Error Log, press the >YES button for a display of: Error Log #1 <...

  • Page 67: View Alg Nums

    To exit, press the NO< button for a display of: Diags: Top Level View Alg Nums > UTILITY MENU (Options Button) The Utility Menu will provide several tools for troubleshooting an MPX G2. The following is a list of the tools available: Repeat Test Last Test Result...

  • Page 68: Test Result Menu

    MPX G2 Service Manual MIDI SRAM 2186 SRAM DRAM 2186-Lex Auto Execution Sample Rate Digipot When the OPTIONS button is pressed, the display will read the following: Repeat test 1 times The OPTIONS LED will flash about once every second instead of being on continuously.
  • Page 69 Lexicon * Note: X = The amount of times the test failed. If a test failed, pressing the >YES button again will display detailed information on the test. The information displayed will represent specific details depending upon which test was run. The following are examples that explain how to interpret the information.
  • Page 70 MPX G2 Service Manual (This is an example where the MIDI Input didn't receive any data.) Test #10 A:0002 <S:00FF R:0000 To exit, press the OPTIONS button and the previous selection will be displayed. DRAM Failure (11) When the DRAM Test fails, Address, Data Sent and Data Received fields are used. All of these fields will display the information in hex.
  • Page 71 Lexicon <S:0000F R:FFFF0 LABUS1 shorted to ground- Add Test A:00000 <S:0000F R:0202F LABUS2 shorted to ground- Add Test A:00000 <S:0000F R:0404F LABUS3 shorted to ground- Add Test A:00000 <S:0000F R:0808F LABUS4 shorted to ground- Add Test A:00000 <S:0000F R:1010E LABUS5 shorted to ground- Add Test A:00000 <S:0000F R:2020D...
  • Page 72 MPX G2 Service Manual In order to determine which bit is bad, the Sent and Received information (which is in hex) must be converted to binary notation as follows: The data sent and data received values in this nibble are different.
  • Page 73 Lexicon 2186 SRAM Failure (14) When the 2186 SRAM Test fails, Address, Data Sent and Data Received fields are used. All of these fields will display the information in hex. The Address field will display what the Address (ADDR0-ADDR13 &A14) was at the time of the failure.

  • Page 74: View Dram

    MPX G2 Service Manual View DRAM This utility allows the operator to view the data stored in the DRAMs (U78-U82). The utility becomes useful when the operator determines which bit is at fault when using the information stored in the Last Test Result utility.

  • Page 75: Removing The Top Cover

    The following test procedures are provided for checking power supplies, system clocks, and battery voltages. As the following procedures require removal of the MPX G2 cover, it is imperative that these tests be performed with regard to all safety and ESD precautions.

  • Page 76: Battery Voltage

    Main board above J4 Battery Voltage: 1. Turn the MPX G2 off and detach the power cord. 2. Set the DMM for a DC voltage on the 20 volts DC scale. 3. Locate battery just to the Left of the power supply 4.

  • Page 77: Systems Clocks

    Lexicon Systems Clocks: These procedures verify the major crystals and other clocks that are important to the operation of the MPX G2. A frequency counter and oscilloscope are required for the following tests. The oscilloscope’s ground lead should be connected to the digital ground Pin 16 of U93.
  • Page 78 MPX G2 Service Manual E32 - extract param alg num error E33 - extract param size error E34 - compact param alg num error E35 - compact param size error E36 - "will fit" param size error E37 - "get size" param size error E38 - "get size"...

  • Page 79: Chapter 6 Theory Of Operation

    EQ and distortion. When the MPX G2 is used with a guitar amp, the guitar is plugged into the MPX G2 input and the MPX G2 send goes to the guitar amp input. This gives the user DSP before the guitar amp for wah-wah, phaser, and other predistortion effects.

  • Page 80: Input

    MPX G2 Service Manual In parallel mode, the DSP switches are set to loop and the mix switches are on. This treats the post- dynamic gain DSP as if it were in a parallel effects loop. Input This section is found on page 7 of the main board schematic. There are two input jacks: one on the front panel (front panel input board scheme) and one on the rear panel.

  • Page 81: Tone Block

    Lexicon corner frequency is 20 kHz. This filter takes a differential signal and sums it to make it single-ended. Therefore its output is 8.2 dBu. R314 forms an attenuator with R315. This brings the signal level back down to 2.2 dBu.

  • Page 82: Send

    MPX G2 Service Manual monitors the signal at the clip LEDs with a peak detector, U35. This signal is amplified, inverted FEEL GOOD and offset in a positive direction by U33b. The amount of gain and offset are varied by U31a. This signal is sent to the cathode of clip LED D39 and inverted by U33a and sent to the anode of clip LED D40.

  • Page 83: Aux Inputs (Including Speaker Simulator)

    Lexicon Aux Inputs (including Speaker Simulator) AUX INPUTS The aux-input circuit is found on page 13 of the main board schematic. The aux input jacks, J8 and J9, each have a switch that senses when a plug has been inserted and sends out a logical high on the corresponding insert status line.

  • Page 84: Output

    MPX G2 Service Manual Q25- Q27 enable and disable the soft-sat. When the soft-sat line is low, Q26 is off and Q27 is on. With Q26 off, the bases of Q24 and Q21 are at 5 volts, which disables them. With Q27 on, Q25 is off and the bases of Q23 and Q22 are at -5 volts, which disables them.

  • Page 85: Digital

    Lexicon Digital ARCHITECTURE The Z80 handles the system software. The 2186 deals with signal routing and non-reverb DSP. The Lexichip does the reverb. The FPGA soaks up most of the discrete logic, and includes a MIDI UART. The EPROM holds the program information for the z80 and the 2186 as well as configuration data for the FPGA.
  • Page 86 MPX G2 Service Manual Memory Map: The EPROM is divided into 8 32K banks. The Z80 selects the bank by writing to the I register, whose contents are placed on the high address bus during refresh. The three extended address lines (labeled...
  • Page 87 Lexicon Here is how this area is mapped: ADDRESS VIEW FROM Z80 VIEW FROM Z80 VIEW FROM 2186 RAM_A14 = 0 RAM_A14 = 1 0x4000 SRAM LOAD SRAM 0x4400 (used by 2186 (used during 0x4800 during boot and boot and...
  • Page 88 SELECT_FOOT. Determines whether the footpedal or the front panel pots will be converted by the DSP's integrating ADC. When 1, the footpedal is selected. When 0, one of the pots is selected. Bit 5 is new to MPX G2. REGISTER 2 WRITE:...
  • Page 89 Lexicon I/O Map To reduce the load on the system data bus, the I/O bus is isolated from the main bus with a transceiver (see Sheet 4 description under Schematic Walk-through). The direction of the transceiver is controlled by the A0 line. Thus, all odd I/O addresses must be writes and all even addresses must be reads.
  • Page 90 MPX G2 Service Manual ; old15, 17 _RESET_ADC resets the ADC when low (new for MPX G2) 19, 1B _RESET_DAC resets the DAC when low 1D,1F MIX_INSERT (new for MPX G2) These signals are initialized to 0 by _RESET. DISPLAY 1 (U74, sheet 3):...
  • Page 91 Lexicon BLUE_WR1 (U64, sheet 5) bit 0 SEND_SELECT bit 1 _DSP_BYP bit 2 FEEL_GOOD bit 3 SHELF bit 4 HIGH_PEAK bit 5 DSP_BYP bit 6 OVL LED (active high) bit 7 LVL LED (active high) These signals are initialized to 0 by _RESET1.

  • Page 92: Schematic Walk-Through

    MPX G2 Service Manual SCHEMATIC WALK-THROUGH SHEET 1: This sheet shows the Z80 and 2186 wire-ORed onto the data and address busses. As the 2186 doesn't drive A14 and A15, these lines are pulled high and low, respectively, when the 2186 owns the bus. The values of R215 and R216 are a compromise to quickly bring the address lines to their correct values once the Z80 relinquishes the bus and not to pull too hard.
  • Page 93 Lexicon Writing to octal D-flop U72 sets the LCD access mode. The Z80 sets LCD_READ if the next LCD access will be a read, and clears it if the next access will be a write. The Z80 also sets LCD_ADDR1 if the next access will be data transfer, and clears it if the next access will be command or status.
  • Page 94 With an addressable latch, it is easier to set and clear individual bit. SHEET 5: Sheet 5 includes the inputs, the LCD interface, the MPX G2-specific control signals, and the pedal A/D converter. U75 reads the multiplexed switches from the right front panel, the encoder, and the footswitches. R646- R649, C554 and C556 help to debounce the encoder.

  • Page 95: Details

    Lexicon SHEET 18: This sheet includes the reset circuit and SRAM battery backup. During power-up, U43 pin 1 pulls _RESET to ground until the voltage at pin 2 rises above approximately 4.3V. R195 and C208 form a power-on delay. R195 charges C208, which keeps Q20 turned on until its base reaches Vcc-1.2V.
  • Page 96 MPX G2 Service Manual performs a synchronization. When this is completed, the 2186 will own the bus about 30% of time, starting just after the rising edge of FS (located above U15). Power-up is complete. FPGA Serial Communications The serial data is clocked to/from the A/D and D/A converters at 128FS. A quadrature word clock (FS_QUAD) allows muxing four channels of A/D and D/A into a single serial port.

  • Page 97: Chapter 7 - Parts List

    Lexicon Chapter 7 - Pa r ts List Main Board ■ PART NO. DESCRIPTION EFFECTI INACTIVE REFERENCE 200-12358 POT,RTY,5K25AX2,7MMFL,14,20L 1.00 202-00499 RES,CF,5%,1/2W,27 OHM 2.00 R348,349 ■ 202-00525 RES,CF,5%,1/4W,510 OHM 1.00 10/06/98 ECO (RY1/C38) ■ 202-09296 RES,CF,5%,1/8W,1K OHM 1.00 10/06/98 ECO (R230/R232)
  • Page 98 MPX G2 Service Manual ■ PART NO. DESCRIPTION EFFECTI INACTIVE REFERENCE R279,281,283,285 R286,300-304,317 R320,322-325,328 R341,342,352 R421,429,432,446 R447,450,455 ■ 203-10896 RESSM,RO,1%,1/10W,1.00K OHM 48.00 10/06/98 R3,43-46,55,60 R64,65,71,80,105 R110,135,141,164 R170,171,177,178 R229,258-261,306 R307,340,345-347 R350,393,395,397,399 R401,403,405,407 R412-414,437,439 R441,443,445 ■ 203-10896 RESSM,RO,1%,1/10W,1.00K OHM 49.00 10/06/98 R3,43-46,55,60,64...
  • Page 99 Lexicon ■ PART NO. DESCRIPTION EFFECTI INACTIVE REFERENCE 203-12497 RESSM,RO,1%,1/10W,8.25K OHM 2.00 R124,148 203-12499 RESSM,RO,1%,1/10W,45.3K OHM 1.00 R163 203-12523 RESSM,RO,1%,1/10W,6.98K OHM 1.00 R176 203-12896 RESSM,RO,1%,1/10W,147 OHM 1.00 R188 203-12897 RESSM,RO,1%,1/10W,976 OHM 2.00 R33,34 203-12898 RESSM,RO,1%,1/10W,47.5K OHM 2.00 R101,102 203-12934 RESSM,RO,1%,1/10W,82.5 OHM 2.00...
  • Page 100 MPX G2 Service Manual ■ PART NO. DESCRIPTION EFFECTI INACTIVE REFERENCE C116,120,121,123-129 C131,132,137,138,140 C141,143,144,147,149 C160-164,166,169-171 C173-176,178-181,183 C184,186-192,194 C197-199,202-204 C206-209,211,214,216 C217,222,223,229,230 C232,233,235,236,240 C242-248,251-254 C256-259,263,264,266 C267,271,272,276,277 C281,282,289,290,298 C299,301,304,306,310 C313,316,319,320 C323-325,328,329 C334-337,342,343,347 C348,353,357-362 C364-370,373-381 C384-386,389-394 C396-402,405,407-412 C418,419 ■ 245-12486 CAPSM,CER,5600pF,50V,COG,20% 7.00 08/18/98 C89,286,288,295...

  • Page 101: Display Board

    10/06/98 RY1/C38 RESISTOR 740-11287 LABEL,S/N,PCB,PRINTED 1.00 Display Board 430-11088 LED,DSPLY,7-SEG,GRN,3DIG,.56 1.00 DISP1 680-11587 CABLE,079,SCKT/SCKTRA,12C,2.5" 1.00 710-11530 PC BD,DSPLY,MPXG2 1.00 MPX G2 FRONT PANEL POT BOARD 200-11570 POT,RTY,CONC,10K25AX3,12,35L 1.00 200-12173 POT,RTY,PC,10KBX2,6MMFL,16,30L 3.00 R1-3 240-11827 CAPSM,ELEC,10uF,16V,20% 1.00 245-12485 CAPSM,CER,.1uF,25V,Z5U,20% 2.00 C2,3 340-11573 ICSM,LIN,NJM4580,DUALOPAMP,SOP 1.00...

  • Page 102: Front Panel Input Board

    MPX G2 Service Manual ■ PART NO. DESCRIPTION EFFECTI INACTIVE REFERENCE 510-12874 CONN,POST,100X025,HDR,2MC,PCRA 2.00 J3,4 710-11529 PC BD,FP POT,MPXG2 1.00 Front Panel Input Board 202-11074 RESSM,RO,5%,1/4W,510 OHM 1.00 203-10896 RESSM,RO,1%,1/10W,1.00K OHM 1.00 203-11744 RESSM,RO,1%,1/10W,1.00M OHM 1.00 244-10423 CAP,MYL,.22UF,10%,RAD 1.00 245-09895 CAPSM,CER,10pF,50V,COG,10% 1.00...

  • Page 103: Packaging/Miscellaneous

    BOX,21.5X5.38X20,BLANK 1.00 OUTER BOX 730-11364 INSERT,FOAM,ENDCAP,1UX9&12 2.00 730-11444 INSERT,CORR,ACC,21X4.5 1.00 730-11541 CERTIFICATE,CE,MPXG2 1.00 730-11543 BOX,21X5X19,MPXG2 1.00 INNER BOX 740-07693 LABEL,LEXICON DIG AUDIO,3"X5" 2.00 Power Cords 680-09149 CORD,POWER,NA/IEC,SVT,VW-1,10A 1.00 680-08830 CORD,POWER,IEC,6A,2M,EURO 1.00 680-10093 CORD,POWER,IEC,5A,2M,UK 1.00 680-10094 CORD,POWER,IEC,6A,2M,ITALY 1.00 680-10095 CORD,POWER,IEC,6A,2M,SWISS 1.00...

  • Page 105: Schematics

    Lexicon Chapter 8 Sche m atics and Drawings Schematics: 060-11528 SCHEM,MAIN BD,MPXG2 060-11539 SCHEM,DSPLY BD,MPXG2 060-12883 SCHEM,FP POT BD,MPXG2 060-12892 SCHEM,FP INPUT BD,MPXG2 Drawings: 080-11563 ASSY DWG,CHASSIS,MPXG2 080-11564 ASSY DWG,SHIPMENT,MPXG2 080-11538 PC,ASSY DWG,DSPLY BD,MPXG2 080-12882 PC,ASSY DWG,FP POT BD,MPXG2 080-12891...
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  • Page 165 Lexicon, Inc. 3 Oak Park Bedford, MA 01730-1441 Tel: 781-280-0300 Customer Service Fax: 781-280-0499 Email: csupport@lexicon.com www.lexicon.com Lexicon Part No. 070-14395 Rev 0 Printed in U.S.A.

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