Lexicon MC-1, Service Manual

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MC-1 Service Manual
5-10
REMOTE (IR) Test
This test verifies the functionality of the IR Remote. Press a key on the remote and verify that the VFD
displays which IR remote button was pressed. The hex display on the VFD remains unchanged until
another remote key is pressed. While the remote key is being pressed the IR acknowledge LED will flash
and the VFD displays the message "ir", (without the quotes), next to the hex value. To exit the test press
and hold the BYPASS F.P. button and then press the MUTE F.P. button. When you have successfully
exited the test the VFD will display an arrow on the left side pointing to the word REMOTE.
LOOP SPI (56004 Loop) Test
The LOOP SPI Test allows one to take the 56004 out of the data path and verify if the problem in the MC-1
the 56004 or the supporting circuitry. To run the test, move jumper W5 to the TEST position, pins 2&3.
Then press the MUTE F.P. button to run the test. This will pass serial data out of U63 pin 9,
SER_CTRL_DATA, to U61 pin 14. Normally during the 56004 SPI Test the data at U61 pin 14 is from the
56004.
SOFTKNOB (VOLUME) Test
This test verifies that the VOLUME knob can be read as it is rotated clockwise and counter clockwise. After
the test has been dialed up on the VFD press the F.P. MUTE button to run the test. A number indicating the
VOLUME knob position comes up on the right side of the VFD. The number display range goes from 00 to
35, indicating the 36 positions of the encoder. As the VOLUME knob is rotated clockwise an arrow pointing
to the knob will display indicating clockwise rotation. If the VOLUME knob is rotated counter clockwise the
arrow points away from the VOLUME knob.
Audio I/O Test:
This test configures the MC-1 to pass audio data through the A/D, DSP, and D/A circuitry without any DSP
effects processing. This test is utilized to verify the audio specifications and allows an MC-1 to emulate
Audio Precision ATE testing on the bench for the purpose of debugging failures.
The audio test modes allow for operating the hardware at a basic level, for proving the functionality of
individual hardware elements. These tests are command-driven, as opposed to the normal menu-driven
operation. The commands fall into two categories.
The first category is Default Commands. There are a few commands that set all relevant hardware to
specific default conditions, regardless of previous history. The other category is Elementary Commands,
which deal directly with the various register bits, either individually or in small associated groups.
To achieve a particular configuration to test, the idea is to issue a Default Command to establish an
appropriate known condition that is close to the desired condition, and then any deviation from the default is
achieved using elementary commands.
Troubleshooting Problems
Problems with the MC-1 usually fit into one of three categories: user interface, audio, or video problems.
User interface problems can range from a nonfunctioning remote or front panel control to user error to no
display. Audio problems involve the signal quality from the analog or digital audio inputs and outputs. Video
problems affect the presence of the On-Screen display or the quality of the video signal being switched
through the MC-1. Some symptoms can be traced directly to a particular sub-system, while others can be
caused by multiple sub-system failures.
When a problem is encountered, it is good practice to verify the overall operation of the MC-1 by running all
of the tests in the Proof-of-Performance section and the Diagnostics.