Bose 1600 vi 1800 v vi amplifiers troubleshooting guide

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1800 SERIES V/VI AMPLIFIERS
TROUBLESHOOTING GUIDE

Refer to the 1800 Series V service manual, part number 181812 and the 1600/1800 Series VI
service manual, part number 199747, for schematics, PCB layouts and part lists.

This procedure will allow you to operate a failed amplifier at low voltage in order to troubleshoot it
more easily. The voltages listed are approximate and will vary slightly in your amplifier due to compo-
nent tolerances. Follow the steps listed below. These steps will allow you to isolate the different
boards of the amplifier to allow easier troubleshooting.

1. Remove the top cover of the amplifier using the disassembly/assembly procedures located in the
service manual.

2. On the bottom of the amplifier, remove the two screws nearest the center of the unit that secure
the power transformer into the chassis. Loosen the other two transformer screws, but DO NOT
remove them. This will allow the access needed for later steps.

3. On the power supply board, remove the large ribbon cable connector at J2. This ribbon cable runs
from the power supply board up to the amplifier board. You may need to slide the power transformer
toward the front panel slightly to do this. Refer to the service manual for PCB locations if necessary.

4. At the Input/Output PCB, remove the three cables at J3, J100 and J200. J100 and J200 run from
the amplifier board to the [/0 board and J3 runs from the I/O board to the display board at the front of
the amplifier.

Caution: Observe all safety precautions when operating this unit with the top cover removed.
Dangerous and possibly lethal voltages are present inside the unit.

Note: For the following tests, we will be applying a percentage ofthe full AC mains voltage to the
amplifier in order to troubleshoot it. We will use a US 120V version of the amplifier for our tests. You
will need to adjust the AC mains voltage level applied to your unit in accordance with the AC mains
voltage that your amplifier is designed to use.

Forthe following tests you will need a Variac and a Digital Voltmeter.

5. On the power supply board, apply a short across pins C and A of the triac Q1. These are the top
two pins. This will allow the amplifier to operate at the lower AC mains voltages we will be using.

6. Plug the amplifierAC mains cable into the Variac. Apply AC mains voltage equivalent to one-third of
the full AC mains voltage. In the case of 120V units, this would be 40 VAC.

7. With 40 VAC applied (for a 120V unit), carefully measure the DC voltages on the power supply
board at the locations listed in the following table. Use the ground point located on the power supply
board near the large electrolytic capacitors. You are primarily checking to make sure that none of the
voltages are significantly different from those listed in the table. If all of the voltages at the 40 VAC level
are okay, you would then turn the AC mains voltage on the Variac up to 60 VAC and measure the DC
voltage levels again. If the voltages at this level are okay as well, turn the Variac up to 120 VAC and
check the voltage levels once more to make sure that none of the components are breaking

down under the full AC mains voltage.

©2000 Bose Corporation Part Number 199747-TG1 Rev. 00

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AC Q9 Q14 020 025 D13 D19 02 Q3
mains
40 G+22.0 G-40.0 G+22.4 G-41.0 1+22.4 1-22.0 B+ 15.7 B-15.7
VAC D+40.0 D-19.3 D+41.2 D-19.8 2+19.2 2-20.1 C+20.1 C-20.0
S+21.9 S-40.1 S+22.1 S-41.0 3+22.0 3-22.0 E+15.2 E-15.1
60 G+31.9 G-61.6 G+31.8 G-61.6 1+30.7 1-30.0 B+15.8 B-15.8
VAC D + 60.6 D - 30.1 D + 60.5 D - 30.0 2 + 30.2 2 - 30.3 C + 30.3 C - 30.4
S+30.0 S-61.0 S+31.2 8-615 3+30.1 3-30.0 E+15.3 E-15.2
120 G+56.3 G-106.4 G+56.4 G-106.4 1+56.3 1-52.1 B+16.1 B-16.1
VAC D + 106.9 D - 52.2 D + 107.0 D - 52.2 2 + 52.7 2 - 52.4 C + 52.6 C - 52.3
S+56.4 8-1063 S+56.4 8-1064 3+56.3 3-52.1 E+15.6 E-15.5

Power Supply Voltage table
8. Ifthe voltage levels are okay at the full AC mains level, then progress to the next step.

9. Turn off the AC mains voltage at the Variac. Using an Ohmmeter, make sure that none of the output
transistors are shorted either internally or to the heat sink. Connect the large ribbon cable on the amplifier
board back onto the J2 connector on the power supply. Leave the other 3 smaller cables from the amplifier
board disconnected.

10. Power up the unit at 40 VAC and measure the DC voltages on the output transistors. Again, you are
looking for any significant difference from those listed in the table below.

AC Mains Voltage 28A1302 PNP Transistors 28A3281 NPN Transistors
4OVAC B-0.5V B+0.5V
C-18.8V C+18.5V
E-12.5 mV E+12.0 mV
60 VAC B-0.52V 8+ .51 V
C-29.8V C+29.8V
E-12.2 mV E+12.0 mV
120 VAC B-0.58V B+0.56V
C-53.0V C+53.0V
E-12.2 mV E+12.0 mV

Output Transistor Voltage table

11. Ifthe power amplifier output transistors measure okay, and the DC voltage levels are okay, then you would
move on to the next step.

12. Remove AC mains power. Reconnect the three remaining cables to the Input/Output board at J3, J100
and J200.

13. Power up the unit at 40 VAC and make sure that all is well. If everything seems okay, turn the AC mains
voltage up to 60 VAC and check again. If all is still well, turn the AC mains voltage up to the full 120 VAC level
and check once more. You should have found your problem by now.

14. When you have finished troubleshooting, remove AC mains voltage and remove the short across the triac
Q1. Make sure that all of the cables removed previously have been re-connected. Replace the two trans-
former screws removed previously and make sure that the other two are tight. Replace the top cover using
the disassembly/assembly procedures in the service manual.

Test the unit for proper operation using the test procedures located in the service manual.