REPLACING AC-500 LED BOARD

Remove the chassis from its case, following the written instructions for this procedure. Lay the chassis upside down on a soft surface, being careful not to damage the tone arm. With the controls facing you, the LED board will be on the right. Remove the three screws holding the board in place. The plug connecting the LED board to the preamp is in the upper left corner of the LED board. Carefully lift the board up and off its connecting pins.

To install the new board, carefully line up the plug on the back side (LED side) of the board with the corresponding pins on the preamp board, and gently push down until the LED board stops against the three mounting studs. Replace the three screws to hold the board in place.

ADJUSTMENT

Use a signal generator set for a 1KHz sine wave at approximately 0.25 volt RMS (the level is not critical).

Connect a 10 ohm load to the main speaker output, and connect an RMS voltmeter across the load.

MUSIC CHANNEL:

Set the AUX MUSIC A-B BAL and A-B INPUT controls to about mid-range. Connect the signal generator to either AUX MUSIC INPUT A or INPUT B. Adjust the MAIN phono volume control for an output level of 1.5 volts RMS. Adjust VR1 (right rear of LED board) for 5 LEDs turned on. A level of approximately 20 volts should light all LEDs.

VOICE CHANNEL:

Set the AUX VOICE INPUT LEVEL control to about mid-range. Connect the signal generator to the AUX VOICE INPUT. Adjust the MIC 1 MAIN volume control for an output level of 1.5 volts RMS. Adjust VR2 (left front of LED board) for 5 LEDs turned on. A level of approximately 5 volts should light all LEDs.