








MPX 100
PERFORMANCE VERIFICATION SECTION
FOR SERVICE MANUAL








Author: Jim Ciardelli
Date: 05/1/98
Rev: 2      
Date: 06/15/98
Rev: 3
























Contents:

This document contains a group of tests that verify the basic operation of the MPX 100.


Required Equipment:

Clean, antistatic, well lit work area
Digital Volt Meter
Low Distortion Sine Wave Audio Oscillator
Stereo Headphone Amplifier
2 Audio cables unbalanced and shielded 1/4 phone plug on one end 
and an appropriate connector on the other end for the headphone 
amplifier inputs.
2 Audio cables unbalanced and shielded 1/4 phone plug on one end 
and an appropriate connector on the other end for the Audio Oscillator
output.
9V AC adapter (Lexicon type or equivalent; 1 amp min., 1.9 amp preferred)
Double Footswitch, Marshall Model #FS02 or equivalent 
1/4 to 1/4 stereo phones plug cable (6ft minimum) Switchcraft# 10BK10
or equivalent.

Initial Inspection:

Inspect the unit for any obvious signs of physical damage. Verify that the front panel controls operate smoothly and correctly. ( Refer to the MPX 100 Owner's Manual for detailed explanations of their functionality). Verify that all screws and rear panel jacks are secure, and inspect the AC power supply for any signs of physical damage.

Power Up:

1.  Connect the 9VAC adapter (provided with the MPX 100) to the isolated variable output of the Variac.
 
2.  Connect the 9VAC adapter to the back of the MPX 100 connector label ed Power.

3.  Verify AC current draw is <0.1 Amps 

On normal power up the MPX 100 will run the following Diagnostic Tests. This Diagnostic Test sequence is displayed on the Front Panel LED's for troubleshooting purposes. If any of the Clip (red) LED's remain lit, a diagnostic failure has occurred and the MPX 100 should be repaired before proceeding.


Test No.
Test
  Edit
Bypass
Store
 Tap
   1
ROM Checksum
  0
  0
  0
 1
   2
SRAM
  0
  0
  1
 0
   3
Lexichip 3 WCS
  0
  0
  1
 1
   4
Lexichip 3 Interrupt Timer
  0
  1
  0
 0
   5
Lexichip 3 Audio Data File
  0
  1
  0
 1
   8
EEPROM Checksum
  1
  0
  0
 0

0=OFF
1=ON


Functional Tests:

Setup:

1.  Connect one end of a  5 pin Midi cable to the Midi Out/Thru connector on the rear of the MPX-100 and the other end to the Midi In.

2.  Connect a dual style 1/4 inch Footswitch to the footswitch jack on the rear panel of the MPX-100.
               
3.  Turn the Variation knob to the "12" position on the Front panel.

4.  Power on the MPX 100 while holding down the Bypass button on the Front panel.

5.  When the Level L & R ((green)) LED's are lit, release the Bypass button.

6.  Verify the following LED's are lit as indicated by the table below


Edit
Bypass
Store
Tap
ON
ON
OFF
OFF
 
Encoder/Switch/LED Test :
1.  Set the Variation knob to the # 6 position and verify the following LED's are lit

Edit
Bypass
Store
Tap
OFF
ON
ON
OFF

2.  To enter the Encoder/Switch/LED Test press the Store button once.

Encoder Test:

1.  Verify the Level L ((green)) LED is lit.
 
2.  Turn the VARIATION Encoder one revolution in a clockwise direction one position at a time, and verify the Level L ((green)) LED is turned off after the encoder is turned one complete revolution. This is a indication the VARIATION Encoder has  passed the test.

3.  Verify the Level R ((green)) LED is lit at this time.


4.  Turn the PROGRAM Encoder one revolution in a clockwise direction one position at a time, and verify the Level R ((green)) LED is turned off (after the encoder is turned one complete revolution) to indicate the PROGRAM Encoder passed the test.

5. Verify all of the Front Panel LED's are now off.


Switch/LED Test:

1.  Press and hold down the Right button on the footswitch. Verify the Right ((green)) level LED is on. When released the LED will go out.

2.  Press and hold down the Left button on the footswitch. Verify the Left ((green)) level LED is on. When released the LED will go out.

3.  On the Front panel press and hold the Bypass button. Verify its LED is on. When released the LED will go out.

4.  Press and hold the Tap button on the Front panel. Verify its LED is on. When released the LED will go out.

5.  Press and hold the Store button on the Front panel. Verify its LED is on. 

6.  At this time when the Store button is released the MPX-100 will exit this test. This will be verified when the Store LED goes off and the 2 (green) level LED's come on (to indicate the test has passed).

 
ADC Pot Test:

Note: During the ADC Pot Test, each pot must be varied over its entire range from fully counter-clockwise, to fully clockwise, and back to fully counter-clockwise within 5 seconds. Otherwise the test will fail due to a time-out error. Therefore, the operator should be prepared to move the "MIX" pot as soon as the test is executed.

1.  Turn the Mix, Effects Lvl/Bal & Adjust pots fully counter-clockwise  before the test is executed.  

2.  Set the Variation knob to the # 7 position and verify the following LED's are on.


Edit
Bypass
Store
Tap
OFF
ON
ON
ON

3.  Press the Store button to execute the ADC Pot Test.
    during the test, the Left (green) LED will be lit to indicate the test has been 
    executed , and the Mix pot is now under test.

4. Vary the Mix pot over its entire range from fully counter-clockwise  to fully
    clockwise  to fully counter-clockwise   within 5 seconds after the Left
    LED comes on.

5.  After turning the Mix pot the Left LED will start flashing. This will indicate the test for the Mix pot passed. The Left LED will then go out and the Right (green) LED will now be lit. 

6.  Vary the Effects Lvl/Bal pot over its entire range from fully clockwise  to
     fully clockwise  to fully counter-clockwise  within 5 seconds after the
     Right LED comes on.

7.  After turning the Effects Lvl /Bal pot the Right LED will start flashing. This                                                                                                                                                                                                                   will indicate the test for the Effects Lvl/pot passed. Once passed the Right LED will stay on and then the Left level LED will light.

8.  Vary the Adjust pot over its entire range from fully counter-clockwise  to fully clockwise  to fully counter-clockwise   within 5 seconds after the Left LED comes on.

9. After turning the Adjust pot both LEDs will start flashing. This will indicate the test for the Adjust pot passed. Once passed the Left and Right LEDs remain on. This is a indication the ADC Pot Test is complete. 


Note: The position of the VARIATION Encoder is also displayed on the Front Panel LED's.


Midi Wraparound Test:

1.  Set the Variation knob to the # 9 position and verify the following LEDs are on.


Edit
Bypass
Store
Tap
ON
OFF
OFF
ON

2.  Pressing the Store button once at this time will execute the Midi                                         Wraparound Test.
 
3.  If the test passes the Left and Right (green) Level LEDs will be on.


Listening Test: 

This test will allow you to test audio through the MPX 100 with and  without effects processing. This is helpful in troubleshooting an audio problem that may reside in the analog or digital circuitry. The first part of this test will be setup for no effects in the audio.

Setup:

1.  Using  two of the audio cables for the headphone amplifier, connect the MPX 100 rear L/R outputs to the L/R inputs of the amplifier.

2.  Using the Y connector, plug the single end into the output of  the sine wave audio oscillator, connect the Y end into the L/R inputs of the MPX 100.

3.  Set the headphone amplifier volume control to its lowest level.

4.  For the Listening Test the Audio I/O test in the Extended Diagnostics is 
     used. This test is without any effects.

5.  To enter the Extended Diagnostics, Audio I/O Test mode, Press & Hold the 
     Bypass button while powering on the unit. 

6.  After the Power On Diagnostics have completed, Release the Bypass button
     when the Left & Right Level (green) LED's are lit.

7.  Turn the Variation knob to Position 13, and verify the Front Panel LED's
     (EDIT, BYPASS, STORE & TAP) indicate the current position of the Variation 
     knob in binary.

Edit
Bypass
Store
Tap
ON
On
OFF
ON

8.  Press the Store button to execute the test, and verify the Left & Right Level 
     LED's are lit.

9.  Input  a  1kHz sine wave at 0dBu to the MPX 100.

10. Set the Input, Mix, Output, EffectsLvl/Bal, and Adjust knobs fully clockwise on the  MPX 100.

11.  Put on headphones, then set the headphone amplifier volume to a
      comfortable listening level.

12.  Individually adjust the Input and Output potentiometers of the MPX 100  
      over their entire range.

13.Verify that no pops, clicks, or scratchiness is heard while turning the
      controls.


Effects Listen Test:

1. Turn the Variation knob to position #14 and press the Store button. This will
    exit the MPX 100 out of extended diagnostics and place it into normal
    operating mode.

2.  At this time verify the processed audio has no audible pops, clicks, or distortion.


Shock Test:

1.  Lift each corner of the MPX 100 off the bench 4 inches (4") then drop.

Note: To prevent damaging the unit, keep one corner of the unit touching the bench at all times.

2.  Verify that no audio, or LED intermittence is caused by this action.


Audio Performance:

Oscillator and Analyzer Default Settings

Unless otherwise noted the following settings are used for the audio 
performance tests:

Oscillator			Analyzer

Waveform: Sine		Filter: Off
Output: Unbal		Bandwidth: 22Hz to 22kHz
	    -25(		Inputs 100k( (except Gain=600()
	    Float

Setup:

1.  Connect the appropriate cable between the oscillator output and the 
     MXP 100 Left input.
2.  Connect the appropriate cable between the analyzer input and the MPX 100 Left output.
3.  Turn the MPX 100 front panel Input and Output knobs fully clockwise. 
4.  Turn the MPX 100 front panel Mix knob fully counterclockwise. 
5.  Power cycle the MPX 100 while pressing and holding down the Bypass button. Wait a second or 2 until the Level LED's come on. Then release the Bypass button. 
6.  Turn the Variation knob to #13 and press the Store button. This will place
     the MPX 100 in to the Audio I/O program  setting it up for the following 
     tests.

Gain Test:

This will check the input to output gain characteristic of the MPX 100 through the dry signal path.


1.  Apply a 1kHz signal at 775mV to the MPX 100

2.  Verify an output from the MPX 100 of  1.95 V +/- 0.05V at the Left output.

3. Connect the oscillator output to the MPX 100 Right input.

4. Connect the analyzer input to the MPX 100 Right output.

5. Verify an output of  1.95V  +/- 0.05V at the Right output.


Signal-to-Noise :


This test checks the signal-to-noise through the MPX 100 signal path.

1.  Set the scale on the distortion analyzer to measure -50dBu signal

2.  Disconnect the oscillator from the MPX 100 input, or turn the oscillator off.

3.  Verify that the noise floor is  <90dBr.

4.  Connect the oscillator output to the MPX 100 Left input.

5.  Connect the analyzer input to the MPX 100 Left output.

6.  Repeat the test, verifying the levels at the Left output.


THD+N:

This checks the THD+N through the MPX 100 signal path.

1.  Apply a 1kHz signal at 220mV to the MPX 100 left input.

2.  Adjust the scale on the distortion analyzer to measure % THD+N.

3.  Verify a distortion level <0.05% THD+N at the Left output.

4.  Connect the oscillator output to the MPX 100 right input.

5.  Connect the analyzer input to the MPX 100 right output.

6.  Verify a distortion level <0.05% THD+N at the right output.


 Frequency Response:

This test checks the frequency response of the MPX 100 through the  signal path at the following frequencies.

20Hz, 3kHz, 5kHz, and 20kHz.

1.  Apply a  220mV signal at 1kHz with the analyzer Bandwidth filters off to the 
     MPX 100 Right input.

2. Use the output level at the MPX 100 Right output for the 0DB reference to 
    check frequency response.

3. Verify that the signal level output is within +/- 0.5dB of the reference at
     the above frequencies. 

4. Connect the oscillator output to the MPX 100 Left input.

5. Connect the analyzer input to the MPX 100 Left output.

6.  Repeat the test verifying levels for the MPX 100 Left output.


Power Supply :


1.  Remove cover as described in disassembly / reassembly section.

2.  Plug the power pack of the MPX 100 to the unit .

3.  Set the DMM to measure VD and check the regulated voltages for 
     proper levels.




Supplies 			Location			Range

+5 VD			Marked test 		(4.85-5.25)
				points to the 
				Right of C6

+5 VA				Marked test			(4.75-5.25)
				points to the 
				Left of J6

-5 VA				Marked test			(4.75-5.25)
				points to the 
				Left of J6

Restoring Factory Settings:

Caution, this Procedure will destroy any user settings or registers.

1.  Press and hold the Bypass button after powering up the MPX 100.

2.  Turn the Variation knob to the # 15 position.

3.  Press the Store button.

4.  The MPX 100 will clear the registers then cycle through a normal power up.

5.  It will now be in normal running mode  

3 Oak Park, Bedford, MA 01730  Tel (781) 280-0300, Fax (781) 280-0499
email: csupport@lexicon.com




1





