Lexicon MC-1, Service Manual

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MC-1 Service Manual
4-2
4. Connect the MC-1 Left /Right Front audio outputs to the amplifier Left / Right inputs and the outputs of
the amplifier to a pair of speakers.
5. Slowly increase the volume level on the amplifier to a comfortable listening level and verify that the
audio is free from noise, distortion, or any other audio irregularities.
6. Repeat for all other Main outputs.
Mute Test
For proper Mute testing, the MC-1 must be set to the Full Mute Setting.
1. Set the MC-1 up as described in the listening test above.
2. On the MC-1 remote, press SELECT to access the Main Menu.
3. Press
Menu ▼ until the display reads: Main Menu/Setup.
4. Press SELECT to enter the top of the Setup Menu.
5. Press
Menu ▼ until the Outputs Level Menu is displayed, then press SELECT.
6. Press Menu ▼ until the MUTE LEVEL -30dB is displayed.
7. Press SELECT to display: System Mute Assign/ -30dB.
8. Press
Menu ▼ until the Full Mute is displayed.
9. Press SELECT.
10. Press DONE four times to place the MC-1 back into normal operation.
11. With Audio running through the MC-1 press the MUTE button on the remote and verify that the audio
signal disappears.
12. Press the MUTE button again and verify that the audio signal returns.
13. Repeat steps 1 to 7 above and reset the MUTE LEVEL to –30dB.
Audio Performance Verification:
Performing these tests assures that the audio signal paths in the MC-1 are functional and that the MC-1
meets published specifications. These tests verify the functionality of all main audio paths. The performance
of the A/D and D/A conversion circuitry are checked through gain, frequency response, THD+N, and S/N
Ratio tests.
Input to Record Outputs Test
Setup
1. Attach the audio input cable between the Low Distortion Oscillator and the MC-1 Left VCR input.
2. Attach the audio output cable between the MC-1 Left Record output and the input of the Distortion
Analyzer.
3. Put the MC-1 into Extended Diagnostics mode by powering up the MC-1 while pressing and holding
down both the front panel REC/ZONE2 and EFFECT buttons until Extended Diagnostics appears on
the display.
4. Press the TAPE button on the remote. The display will read AUDIO Test.
5. Press and hold the Shift button on the remote, then press the Off button. The # 99 will then be
displayed next to AUDIO Test.
6. Press and hold the RECORD button on the remote, then press the VCR button. The # 53 will then be
displayed confirming the VCR input is now set to the RECORD outputs.
Tests
1. Apply a 1kHz signal @ +12dB (+4 Vrms) to the input channel.
2. Set the scale on the Distortion Analyzer to m12dBV (+ 4Vrms ) signal level.
3. Turn all filters off on the Analyzer.
4. Verify that the output level from the MC-1 is +12dBV (+4Vrms) +0.2/-0.3dBV.
5. Adjust the scale on the Distortion Analyzer to measure 0.005% THD+N and turn on the 30kHz low pass
or audio bandpass filter.
6. Verify that the THD+N measured is less than 0.005%.
7. Set the scale on the Distortion Analyzer to m12dBV (+ 4Vrms) signal level.