Lexicon MPX 200 Service Manual
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Lexicon MPX 200 Service Manual

24-bit dual channel processor
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MPX 200
24-Bit
Dual Channel Processor
Service
Manual

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  • Page 1 MPX 200 24-Bit Dual Channel Processor Service Manual...
  • Page 2 Copyright © 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 # 070-14827 Rev 0 Printed in the United States of America...
  • Page 3 Lexicon Safety Suggestions Read Instructions Read all safety and operating Power Cord Protection Route power supply instructions before operating the unit. cords so that they are not likely to be walked on or pinched by items placed on or against them,...
  • 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

    Tools ..............................1-1 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 Initial Inspection............................4-1 Functional Tests ............................4-1 Initial Power On Check .........................4-1 Normal Power Up ..........................4-1...
  • Page 6 Lexicon Schematic Walkthrough ........................6-1 Front Panel Board ..........................6-10 Schematic Walkthrough ........................6-10 Chapter 7 - Parts List.................. 7-1 MPX200 MAIN BOARD ASSEMBLY....................... 7-1 MPX200 FRONT PANEL BOARD ASSEMBLY..................7-3 MPX200 MECHANICAL ASSEMBLY ...................... 7-3 MPX200 POWER CORD OPTIONS......................7-3 MPX200 SHIPPING MATERIALS ......................

  • Page 7: Chapter 1 Reference Documents, Required Equipment

    • ¼" phone cable (T/R/S) • Double Footswitch with 15 foot ¼" phone plug cable configured for tip, ring and sleeve, (Lexicon P/N • 750-09277) or equivalent Low Distortion Oscillator with single-ended or balanced output, < 100 ohms output impedance, < .005% •...

  • Page 9: Chapter 2 General Information

    Return Authorization from Lexicon. If Lexicon recommends that a MPX 200 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

    Lexicon Chapter 3 Spec i fications Analog Inputs Connectors: 1/4" unbalanced Impedance: 500KΩ unbalanced for Direct Instrument input (unit detects a mono input on the right input) A/D Dynamic Range: >95dB typical, 20Hz-20kHz, unweighted Levels: -30dBu to +4dBu Resolution: 24-Bit Analog Outputs Connectors: 1/4"...

  • Page 13: Chapter 4 Performance Verification

    (facing the Front Panel). Make sure it is switched to the proper AC voltage setting for your area. 2. Connect the power cord to the back of the MPX 200 and the other end into an isolated variable output power supply (Variac).

  • Page 14: Lexichip3 Adf Test (5)

    2. Press and release the load button to execute the test. 3. The display will read: “r 8”. 4. The MPX 200 is now ready to test both the footswitch functions and the front panel switches. Footswitches 1. Press and hold the Left footswitch (labeled Ring) and observe that the Left –30dB headroom LED is lit.

  • Page 15: Encoder Test (9)

    4. Set the power switch to the OFF position to power off the MPX 200. 5. Disconnect all cables from the rear panel of the MPX 200. I/O Test These tests will verify the audio performance of the MPX 200’s audio input and output circuitry.

  • Page 16: Setup

    Setup Turn on the MPX 200 and wait for the Power On Diagnostics cycle to finish. 2. Set the MPX 200 for Analog in and out by pressing and holding the Bypass button until SYS flashes, then release. 3. Press the Bypass button once. The display will read Src.

  • Page 17: Dynamic Range Test

    This test will verify that the MPX 200 will pass an S/PDIF signal through its input and output circuitry. 1. Connect a Digital signal (CD player, DAT, etc.) to the S/PDIF input jack on the back of the MPX 200.
  • Page 18 MPX 200 Service Manual 1. While listening to the unit with the headphones lift a corner of the MPX 200 off of the table approximately 4 inches and then drop. 2. Verify that there is no loss of audio or distortion during this action.

  • Page 19: 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 200 product. This is provided as a reference and supplement to bench test settings found in the proof of performance in this manual.

  • Page 21: Chapter 5 Troubleshooting

    Power-On Self Tests (POST) Upon normal power up, the MPX 200 will perform a series of diagnostic tests. For a description of these tests, refer to Table 2.1. These diagnostic tests have been designed to take less than 10 seconds. The diagnostic test sequence is displayed on the front panel LEDs prior to the execution of the test wherever possible for troubleshooting purposes (provided the LEDs are functioning properly).

  • Page 22: Diagnostic Failures

    If the Bypass button is pressed after a failure has occurred, the MPX 200 will attempt to continue on with the next test of the POST sequence. The MPX 200 will attempt to do this every time the Bypass button is pressed.
  • Page 23 The Lexichip3 INT test will verify that the Lexichip3 interrupt (INT/) is working and occurring at the proper intervals. The Lexichip3 will provide MPX 200 with the interrupt (INT/) to the Z80's maskable interrupt line. Before the test is executed, the following test code will be displayed on the Diagnostic LEDs:...
  • Page 24 If the Tap/Cancel button is pressed, the CPU will attempt to go into a mode where it can execute the test continuously. NOTE: The first time the MPX 200 is powered on when a new EEPROM part has been installed or the Software version has changed and the EEPROM is initialized, the EEPROM will be initialized during the EEPROM diagnostic test and the 7-segment display will display “rSt”...

  • Page 25: Extended Diagnostics

    Lexicon EXTENDED DIAGNOSTICS The following tests are available in the Extended Diagnostics: 7 Segment Test # Test Name Diagnostic LED LED Display Note: ROM Checksum COMPRESSOR “–20dB” SRAM COMPRESSOR “–10dB” LEXICHIP3 WCS COMPRESSOR “–3dB” LEXICHIP3 INT COMPRESSOR “Threshold” LEXICHIP3 ADF EFFECTS “Echo/Delay”...

  • Page 26: Extended Diagnostic Test Desriptions

    MPX 200 Service Manual The (Green) LEVEL LEDs are lit to indicate when the test has Passed. The (Red) LEVEL LEDs are lit to indicate when the test has Failed. The following tests can be run continuously by pressing the Tap/Cancel button instead of the Load button.
  • Page 27 Lexicon register, and then restoring the value when it's done. The entire contents of the SRAM is tested by writing 00 hex (00000000 binary), and verified by reading the same value back from each memory location. This write/read sequence is also performed using the following patterns: 55 hex (01010101 binary), AA hex (10101010 binary) and FF hex (11111111 binary).
  • Page 28 The Interrupt test will verify that the Lexichip3 interrupt (ZINT/) is working and occurring at the proper intervals. The Lexichip3 will provide MPX 200 with the interrupt (ZINT/) to the Z80’s maskable interrupt line. Before the test is executed, the following test code will be displayed on the Diagnostic LEDs, along with the...
  • Page 29 Lexicon If the test failed, the (Red) LEVEL LEDs will light. EEPROM Test (6) This test will read each byte in the User Register portion of the EEPROM and add them together to calculate a checksum. This value is compared with the checksum value stored in the EEPROM itself. This checksum will be recalculated each time a register is stored.
  • Page 30 MPX 200 Service Manual Pressing the Tap/Cancel button will run the test continuously. When the test is executed, the leftmost 7-segment display will display an “r” to indicate the test is running. The pass/fail status of the test is displayed on the 7-segment displays and front panel LEVEL LEDs.
  • Page 31 Lexicon Encoder Test (9) During the Encoder test, the Z80 microprocessor reads the value of the encoder, and then expects the next value read from the encoder (when the encoder position is moved) will be at a predetermined incremental value. Therefore, during the test the encoder must be rotated in a clockwise direction as it’s being tested, or the test will fail.
  • Page 32 MPX 200 Service Manual Before the test is executed, the following test code will be displayed on the Diagnostic LEDs, along with the test number on the 7-segment displays: 7-segment Test # Test Name Diagnostic LED display EFFECTS “Room” Pressing the Load button will execute the test.
  • Page 33 Pressing the Load button will execute the test. Initialize Test (13) This selection will initialize all of the MPX 200 system parameters to their factory default settings. Before the test is executed, the following test code will be displayed on the Diagnostic LEDs, along with the...
  • Page 34 MPX 200 Service Manual Burn In Tests (16) During the execution of the Diagnostics in the Burn In loop, the appropriate test code will be displayed on the Diagnostic LEDs (BYPASS, STORE and TAP). This code will be sent to the LEDs before each test is executed.

  • Page 35: Service Notes

    Always use caution when testing the unit with the Main PCB removed from the chassis, be sure to place a heatsink (HEATSINK,TO220,.75X.5X.5"H, Lexicon P/N 704-14132 or equivalent) onto the voltage regulator at U25 to dissipate excess heat, and protect it from reaching thermal shutdown.

  • Page 37: Chapter 6 Theory Of Operation

    Lexicon Chapter 6 Theo r y of Operation Main Board Schematic Walkthrough Sheet 1 This sheet shows the analog input circuitry (U1-U2), the analog output (U6), and the output mute circuitry (U7). Input Stage Separate unbalanced ¼” phone jacks (J1-J2) provide input for the left and right signals. A single input source will be routed to both left and right input stages if the right channel (J1) is the only one used.
  • Page 38 MPX 200 Service Manual Output Stage and Muting The output of the CODEC circuitry re-enters this page as signals OUT_LEFT and OUT_RIGHT. Provisions are made for an additional low pass filter of these signals by installing capacitors in locations R45 and R33; additionally, the CODEC signal may be attenuated or “padded” by installing resistors in these locations, but these have not been implemented in the design.
  • Page 39 Lexicon AK4528 CODEC The AKM CODEC AK4528 is a high performance 24-bit A/D-D/A device which performs anti-alias filtering, analog to digital conversion, digital to analog conversion, and digital 15/50uS de-emphasis. Although it supports sampling rates up to 96kHz, the MPX200 only supports 44.1kHz sampling.
  • Page 40 MPX 200 Service Manual S/PDIF Input The S/PDIF input is brought in via one half of J5. The signal is terminated into 75Ω by R129, AC coupled by C103, and amplified by U18 (74HCU04). Current limiting resistor R127 and clamping diode D6 provide input protection.
  • Page 41 Lexicon Read Only Digital Audio Receiver Status ZD Bus Bits Function Auto FS96 Validity Auto: = 1: AC-3 or MPEG Detect = 0: No Detection FS96: = 1: Fs >= 88.2kHz = 0: Fs <= 54 kHz ERF: This bit is the logical OR of PLL, Parity, Biphase, and Frame Length status.
  • Page 42 MPX 200 Service Manual = 0: None of the above switches have been pressed. ENC_3:0: This is a straight read of the rotary encoder switch SW1. Possible values range from 0000 to 1111. Resistors R158 through R161 provide pull-ups for signals ENC_3:0, ensuring that a switch open condition is properly read back as a logic ‘1’.
  • Page 43 Lexicon and the AK4112A. R64 is a provision for bypassing the U14 circuitry, but it is not implemented in this design. Front Panel Connector The front panel connector is not precisely a connector. Rather, it is a 16 x 1 row of solder pads that accept a semi-rigid flat cable that solders directly to the Main PCB and the Front Panel PCB.
  • Page 44 MPX 200 Service Manual Chip Select Buffers U22 currently is the only chip select buffer used on the MPX200. Provision has been made to add a second one (U21) in order to separate out read from write chip selects, but this has not been implemented. Resistor R154 guarantees that chip select signal REG_SEL/ is held in an inactive state during power up.
  • Page 45 Lexicon enables must be pulled high and the Z80 must be fed clocks to allow the resistors to work as designed. Proper initialization of the system is dependent on the static state of the data bus on power up. The PLL TEST Pins are diode clamped by D4 to RESET/.

  • Page 46: Front Panel Board

    MPX 200 Service Manual +5VA This is a filtered and ferrite bead isolated version of the +5VD supply. The current demands on this rail are barely appreciable on U25. FB1 and C64 provide noise isolation and charge reserve for this rail, which is used to power much of the analog domain in the system.
  • Page 47 Lexicon (ROW_REG_[2:0]/), a reset line (FP_RESET/), two front panel switch monitoring signals (SWITCH_ROW[1:0]/) and an eight bit data bus (FRNT_D[7:0]). Octal Registers The purpose of these registers (U2-U4) is to latch the data value presented by the Main Board depending upon which register is selected for activation by the decoded strobes.
  • Page 48 MPX 200 Service Manual LED_ROW18/ DISP3 (Segment C) D8 (-3dB) D42 (Bypass Button LED) LED_ROW19/ DISP3 (Segment B) D6 (R_Signal) D9 (-10dB) DISP3 (Segment A) D43 (Tap/Cancel Button D10 (-20dB) LED_ROW20/ U2 data bits FRNT_D[7:5] are active high and they activate the three columns; the columns are connected to the LED anodes, so the column signals are by necessity active high.
  • Page 49 Lexicon Front Panel Switches Like the LEDs, the switches are arranged in a row-column scheme. The arrangement is in a 3x2 architecture. Whenever a button is pressed, a software scan of the SWITCH_ROW[1:0]/ bits at address 0x4C00 determines which button was pressed. The Column signals used by the LEDs are used here as well.

  • Page 51: Chapter 7 - Parts List

    Lexicon Chapter 7 - Pa r ts List MPX200 MAIN BOARD ASSEMBLY PART NO. DESCRIPTION EFFECTIVE • INACTIVE REFERENCE 120-14142 ADHESIVE,EPOXY,THERM COND 0.00 U10 HEATSINK 200-12169 POT,RTY,5K15AX2,7MMFL,14,15L 1.00 202-09794 RESSM,RO,0 OHM,0805 19.00 R72,82,94 R96-98,102,105-108 R112,146,147,156,165 R166,172,173 202-09795 RESSM,RO,5%,1/10W,2.2K OHM 2.00...
  • Page 52 MPX 200 Service Manual PART NO. DESCRIPTION EFFECTIVE • INACTIVE REFERENCE 245-00596 CAP,CER,.005uF,1.6KV,Z5U 1.00 245-09291 CAPSM,CER,470pF,50V,COG,5% 4.00 C31,32,35,36 245-09876 CAPSM,CER,.01uF,50V,Z5U,20% 3.00 C67,100,103 245-09895 CAPSM,CER,10pF,50V,COG,10% 3.00 C1,16,74 245-10416 CAPSM,CER,1000pF,50V,COG,5% 1.00 C116 245-10544 CAPSM,CER,220pF,50V,COG,5% 4.00 C26,45,61,71 245-10561 CAPSM,CER,100pF,50V,COG,5% 9.00 C5,8,20,23,49,56 C110-112 245-10562 CAPSM,CER,150pF,50V,COG,10% 6.00...

  • Page 53: Mpx200 Front Panel Board Assembly

    Lexicon PART NO. DESCRIPTION EFFECTIVE • INACTIVE REFERENCE 740-11287 LABEL,S/N,PCB,PRINTED 1.00 740-14690 LABEL,FUSE,CAUTION,250MA/250V 1.00 PCB NEAR FUSE •03/07/01 MPX200 FRONT PANEL BOARD ASSEMBLY PART NO. DESCRIPTION EFFECTIVE • INACTIVE REFERENCE 202-09795 RESSM,RO,5%,1/10W,2.2K OHM 2.00 R28,29 202-09871 RESSM,RO,5%,1/10W,1K OHM 3.00 R1-3...

  • Page 54: Mpx200 Shipping Materials

    MPX 200 Service Manual PART NO. DESCRIPTION EFFECTIVE • INACTIVE REFERENCE 680-10094 CORD,POWER,IEC,6A,2M,ITALY 1.00 680-10095 CORD,POWER,IEC,6A,2M,SWISS 1.00 680-10096 CORD,POWER,IEC,6A,2M,AUSTRALIA 1.00 680-10097 CORD,POWER,IEC,6A,2M,JAPAN 1.00 680-10098 CORD,POWER,IEC,6A,2M,UNIVERSAL 1.00 MPX200 SHIPPING MATERIALS PART NO. DESCRIPTION EFFECTIVE • INACTIVE REFERENCE 070-14692 GUIDE,USER,ERRATA,MPX200 1.00 •03/27/01...

  • Page 55: Schematics

    Lexicon Chapter 8 Sche m atics and Drawings Schematics 060- 14659 SCHEM,MAIN BD,MPX200 060- 14669 SCHEM,FP BD,MPX200 Drawings Component Layout - Main Board, MPX200 Component Layout - Front Panel Board,MPX200 080-14718 ASSY DWG,CHASSIS,MPX200 080-14719 ASSY DWG,SHIPMENT,MPX200...
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  • Page 90 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. 070-14827 Rev 0 Printed in U.S.A.

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