3 Oscillation

Defective U1 Defective CR1, 2, 6, 15 Open ground at the RCA input jack Defective Q1-8, Q24 Defective CR16, 17 Short between transistor and heat coupler Shorted driver or output transistor Test point A polarity the same as DC offset (see Figure 11) Test point A polarity opposite to the DC offset (see Figure 11) Trouble shoot (by removing collector screws) in this sequence. Negative Q9, 11, 23, 21, 22, 19, 20, 18 Positive Q6, 10, 17, 16, 14, 13, 12, 15

Bose Service Manual

All resistors are 1 2W 5 unless otherwise stated. 3. For 0 dB LED indication, amplifier output is 2 Volts at 8 Ohms. 1. See Bias Adjustment Procedure. 2. U1 input pin 2 virtual ground, output test point 8 pin 6 275mV. 3. Early production units replace R28 with capacitor C15 0.1 uF found in either side of the pc board. 4. All resistors are 1 2 watt 5 unless otherwise specified. 5. All capacitor in uF unless otherwise specified. C8 200pF 10 '200V R51 3400 1 1 4W

1801 Power Amplifier

Note Refer to Figure 5 for the following procedures. 9.2 Unsolder the wires to the LED PCB and make a note of the wiring configuration. 9.3 Remove the center nut located on each side on the LED lamp housing. 9.4 Lift the LED assembly out from the front chassis. 9.5 Disassemble the LED assembly to gain access to the PCB. Note Remember how the lamp housing spacers are placed. 10.1 After reassembling the LED assembly, place it onto the front panel assembly and secure it in place. 10.2 Resolder the...

7Excessive Distortion

Bose 1801 220volt

Defective C5 Defective Q6, Q9 Defective CR8 Open C4, 5, 9, 11 Defective R24, 29, 30, 51, 52 Defective Q4, 6, 7, 9 Open R11, 12, 13 Defective C5, C8 Shorted Mica Insulator Q3 Defective Q7, Q8, Q25 Defective CR18, 19 Defective CR5 at full output only 1. Perform Top Cover removal procedures for the model amplifier your going to convert. 2. Refer to the figures below for the voltage conversion being performed. 3. On the 1801 when converting to 110 volts remove the in-line resistor found wired to...

6Thermal Cutoff Procedure

110v Omin Relay Diagram

6.1 Apply a signal to the unit with the outputs loaded 8 or 4 ohms . Short one channel at a time until the unit goes into thermal cutoff. The thermal indicator should turn on and the output of the unit should be off. 6.2 Disconnect the short from the output. Wait until the unit comes out of thermal cutoff. You can speed this process by cooling the PCB with a fan. 6.3 Once the unit is cooled apply a signal to the channel you had shorted to check to see if its operational. 6.4 Apply a signal to...

Bose 1800 Service

Safety Electrostatic Discharge Sensitive ESDS Device Disassembly Assembly Test Figure 1. 1801 Component Figure 2. 1801 Side Figure 3. 1800 Front Figure 4. 1800 Rear View of Front Figure 5. 1801 Rear View of Front Figure 6. 1800 Rear Figure 7. 1801 Rear Part List Figure 8. 1801 Front Part Figure 9. 1801 1800 Block Figure 10. LED PCB Figure 11. LED PCB Schematic Diagram Figure 12. Amplifier Schematic Figure 13. Amplifier PCB Troubleshooting Voltage Conversion Service THIS DOCUMENT CONTAINS...