Voltage Conversion Instructions; 120 To 240 Voltage Conversion; 240 To 120 Voltage Conversion; Fm 50 Microsecond De-Emphasis Change - Bose 550 Service Manual

VOLTAGE CONVERSION INSTRUCTIONS

Refer to Figures 11 and 12 for the following procedures

120 to 240 Voltage Conversion

1. Locate the brown and yellow power transformer wires, remove the crimp insulator, and
separate the wires.
2. Tape or insulate the brown wire (this wire is not used for 240 volt wiring, but it will be
needed to convert back to 120 volt wiring).
3. Cut or unsolder the orange wire at the switched outlet and connect it to the yellow wire.
Tape or insulate the connection.
4. Replace any tie-wraps that were removed from the wiring harness.
5. Replace the line fuse with a 1.5 amp 250 volt fast blo fuse.
6. Add a label to the rear panel indicating the voltage conversion to 240 volts.

240 to 120 Voltage Conversion

1. Locate the orange and yellow power transformer wires, remove the crimp insulator, and
separate the wires.
2. Solder the orange wire to the switched AC outlet terminal with the gray transformer wire
connected to it.
3. Locate the brown wire and remove the crimp insulator or tape.
4. Connect the yellow and brown wires together and tape or insulate the connection.
5. Replace any tie-wraps that were removed from the wiring harness.
6. Replace the line fuse with a 2.5 amp 250 volt fast blo fuse.
7. Remove the 240 volt label on the rear panel of the unit indicating the voltage conversion.

FM 50 Microsecond De-Emphasis Change

1. Change R61, R62 from 2.2k to 1k ohms.
2. Change R63, R64 from 3.3k to 2.2k ohms.
3. Remove C65 and C66 (.0056 uF).
4. Change C67, C68 from .0056 to .0033 uF.
5. Change C69, C70 from .0015 to .0068 uF.
To Convert to 75 Microsecond De-Emphasis reverse the above Procedure.
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