CHANGING LINE VOLTAGE RATING
ADJUSTING BIAS
The 9130 Amplifier is equipped with a simple means to adjust the AC line voltage rating for 100, 120 or 230 volts AC, 50/60 Hz. The configuration is labelled above the power cord connector. If the amplifier will be used in a location that requires a different line voltage, use the following procedure to change the configuration. Review the modification instructions before attempting this procedure. If any doubts exist about one’s ability to change the line voltage, it is advisable that the procedure be conducted by a qualified technician.
NOTE: Units wired for 230 VAC may be used over a range of 220 to 240 VAC. No compromise in safety or performance will result from operation within this range.
WARNING! UNPLUG THE UNIT FROM AC POWER BEFORE ATTEMPTING THIS PROCEDURE. FAILURE TO DO SO CAN RESULT IN SEVERE ELECTRICAL SHOCK.
1)Remove the top cover by removing the four hex head screws (two on each side).
2)Using the diagram “Component Layout” as a guide, find the white Voltage Selector plug on the printed circuit board located behind the front panel Power Switch. Note that this plug has several alternate positions. Each position is labelled for where the end of the plug is to be aligned for each appropriate voltage. Move this plug to the new desired position, making sure that the plug is fully seated on the mating pins.
3)Depending upon which new voltage is chosen, it may be necessary to change the AC line fuse. Locate the
a new
100 and 120 VAC: 5 amp
230 VAC: | 2.5 amp |
NOTE: For units wired at
4)Replace the cover.
5)Obtain a new voltage configuration label from the factory, and affix over the original markings on the rear panel. Alternately, prepare a small
permanent ink. Relabelling the unit is a vital safety requirement, particularly if the amplifier is sold to a new owner.
The 9130 Amplifier employs a single control per channel to set the bias operating point of the output stage. This bias point is factory set, and normally should not require adjustment for the life of the product. However, should improper bias be suspected, or if repairs have been made that would require a readjustment of bias, the following procedure should be used. Review the instructions before attempting this procedure. If any doubts exist about one’s ability to set the bias, it is advisable that the procedure be conducted by a qualified technician.
WARNING! UNPLUG THE UNIT FROM AC POWER BEFORE ATTEMPTING THIS PROCEDURE. FAILURE TO DO SO CAN RESULT IN SEVERE ELECTRICAL SHOCK.
REQUIRED TEST EQUIPMENT: Milliammeter capable of measuring at least 130 mA.
1)Remove the top cover by removing the four hex head screws (two on each side).
2)Using the diagram “Component Layout” as a guide, find the fuses labelled Fl and F2 for the left channel, or Fl 01 and F102 for the right channel.
3)Working on one channel at a time, remove either one (and only one) of the fuses. Connect the
milliammeter to the two fuse clips, and set the meter to a scale capable of measuring at least 130 mA.
WARNING! THE NEXT STEP OF THIS PROCEDURE CAN EXPOSE THE OPERATOR TO UNINSULATED HIGH VOLTAGES. KEEP ALL BODY PARTS CLEAR OF THE INTERNAL CIRCUITRY OF THE AMPLIFIER.
