Midi Test - Lexicon MPX G2 Service Manual

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. The test also
verifies that pin 50 (MIDI IN) and pin 51 (MIDI OUT) of the FPGA chip (U84) is working.
To check the MIDI Output to Remote/In, a 5 Pin Male DIN to 5 Pin Male DIN Pin Cable (also known as a
MIDI Cable) must be connected between the Remote/In jack and the MIDI OUT jack.
To test the MIDI Output at the Remote/In jack (J14 pin 3), a 5-pin DIN Male plug must be installed at J14
and the plug must be wired as follows:
- Jumper pin 3 to pin 5. This will connect the MIDI Output to the MIDI Input of J14.
- Jumper pin 1 to pin 4. This will enable the OPTO Isolator 6N138 (U9) so it can pass the MIDI
Data through Pin 2 of U9. Pin 2 gets pulled high (+5V) when the DIN plug is connected to J14.
In Manufacturing, a MIDI Comparator fixture was designed to verify both MIDI outputs are working. It was
designed to reduce the test time when verifying the operation of the MIDI circuits. The following equipment
is required when using this fixture:
- 5 Pin Male DIN to 5 Pin Male DIN Pin Cable (3 feet Minimum). Also known as a MIDI Cable.
- 7 Pin Male DIN to 7 Pin Male DIN Pin Cable (3 feet Minimum). Also known as a MIDI Cable.
- MIDI Comparator Fixture (TEG P/N 770-90096).
- Remote Power In Power Supply Tester (TEG P/N 770-90097).
The following setup is required:
- Using the 7 Pin DIN cable, connect one end to the jack on the rear panel of the UUT
labeled "Remote/In" and the other end to the jack on the MIDI Comparator Fixture labeled
"OUT".
- Using the 5 Pin DIN cable, connect one end to the jack on the rear panel of the UUT
labeled MIDI Out and the other end to the jack on the MIDI Comparator labeled "In".
- Using the Remote Power In Power Supply Tester, connected the single ended plug to the
jack on the rear panel of the UUT labeled "Remote Power In".
- Power on the Remote Power In Power Supply Tester and verify the LED on the MIDI
Comparator Fixture is lit.
At the Functions Tests menu turn the Encoder until the display reads the following:
Next press the STORE button and release.
If the test passed, the display reads:
Diags: Top Level
Test >
Diags:Tests
< MIDI
MIDI Test
Passed (done)
Lexicon
5-13