Yamaha DA824, Руководство по обслуживанию

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DA824
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Slot power supply peripheral connection check
Only the NG systems from the test results will be shown on the screen.
[5] WC BNC
Displayed on the screen when the results of the word clock IN terminal/ JK901 and CPU connection are NG.
4. Manual inspections
In addition to the automatic tests, the residual noise is measured.
1. Measurement conditions
· 0 dBu=0.775 Vrms
· The input Impedances of the oscilloscope and the level meter should be more than 100 k ohms.
· The measurement is corrected by 12.7 kHz, -6 dB/OCT LPF.
· The load for output 1 to 8 is 600 ohms.
· Output 1 to 8 is measured at the cannon connector.
· The internal gain SW is +18 dB.
· Word clock in 75 ohms is set to on.
· Input the signal only into the channel being measured.
2. Measuring method
In the test program mode, a digital 0 will be output from the slot test jig when the following command is executed.
In this state, a level gauge is used to measure residual noise. Check that the permissible range is less than -92 dBu.
5. System reset
When in the test program mode, entering “reset” and executing the program will reset the system.
DA824_DIAG>zero
DA824_DIAG>
DA824_DIAG>reset
The system is reset.