Vingtor Stentofon VPA-120, Инструкция по установке и обслуживанию

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A100K10876 Installation and Service Manual Page 11
VPA Amplifiers
4.1.3 Speaker line fault detection
A 23 kHz tone is continuously transmitted on the loudspeaker line to
detect faulty lines. The switch on the upper left board (AMP-2) inside the
cabinet should be ON to enable this function.
If the FAULT LED on the front is on without any obvious reasons, or the
first VU-meter LED is lit without any signal source, the pilot tone level
may need adjustment.
z
Set all volume controls to their final levels.
z
Turn the power OFF and remove the cabinet cover.
z
Reconnect the power and locate the trimming pot on the AMP-2
board.
No external signal must be applied to the amplifier.
z
Turn the pot CW until the first green LED (-18 dB) is lit.
Observe that the FAULT LED is off.
z
Turn the pot slowly back CCW until the LED just extinguishes.
Observe that the FAULT LED is off.
The pilot tone level should now be correct.
z
Turn the power off and remount the cabinet cover.
Pilot tone on/off
Fault level