Bose 1801 Service Manual
Contents
Specifications................................................................................................................................... 2
Safety Information............................................................................................................................ 3
Electrostatic Discharge Sensitive (ESDS) Device Handling ........................................................ 4
Disassembly/Assembly Procedures ........................................................................................... 5-8
Test Procedures ............................................................................................................................... 9
Figure 1. 1801 Component Location.............................................................................................. 10
Figure 2. 1801 Side View ............................................................................................................... 10
Figure 3. 1800 Front Panel ............................................................................................................ 11
Figure 4. 1800 Rear View of Front Panel....................................................................................... 11
Figure 5. 1801 Rear View of Front Panel....................................................................................... 11
Figure 6. 1800 Rear Panel ............................................................................................................. 12
Figure 7. 1801 Rear Panel ............................................................................................................. 12
Part List Notes................................................................................................................................ 13
Figure 8. 1801 Front Panel ............................................................................................................ 13
Part List...................................................................................................................................... 14-17
Figure 9. 1801/1800 Block Diagram............................................................................................... 18
Figure 10. LED PCB Layout........................................................................................................... 19
Figure 11. LED PCB Schematic Diagram ...................................................................................... 20
Figure 12. Amplifier Schematic Diagram........................................................................................ 21
Figure 13. Amplifier PCB Layout.................................................................................................... 22
Troubleshooting Guide .................................................................................................................. 23
Voltage Conversion Instructions .................................................................................................. 24
Service Bulletin ......................................................................................................................... 25-28
PROPRIETARY INFORMATION
THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF
BOSE
THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT
BY AN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE
BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED
FOR ANY OTHER PURPOSE.
®
CORPORATION WHICH IS BEING FURNISHED ONLY FOR
1
SPECIFICATIONS
Mechanical
Dimensions: 1801
1800
7 3/16" H x 18" W x 18 1/2" D
(Including Knobs)
81/4"H x 19"W x 15"D
(not including handles)
Weight: 1801
1800
Power Requirements
Voltage: 105-125 AC USA, 210-250 AC EUR
Frequency: 50-60 Hz
Power Consumption: Minimum 60 watts
Integral Design™
Amplifier
Output :
(both channels operating )
Harmonic Distortion:
(THD) @ 250 watts
IM Distortion:
(4:1 60-7kHz) 150 watts
82 lbs
95 lbs (shipping)
80 lbs
91 lbs (shipping)
Normal 1000 watts
Maximum 1960 watts
250/250 watts @8 ohms
400/400 watts @4 ohms
Less Than .15% (20Hz-5kHz)
Less Than .5% (5kHz-10kHz)
Less Than .15%
Frequency Response: 20Hz-10kHz ±.25dB
10kHz-15kHz ±.7dB
15kHz-20kHz ±1dB
Signal to Noise Ratio:
(unweighted)
Load Impedance: 4 ohms or higher
Input Sensitivity: 1.5 Vrms for 250 watts output into 8 ohms
Input Impedance: 50,000 ohms or higher
-100dB ≤.5mV across 8Ω at zero volume
2
SAFETY INFORMATION
1. Parts that have special safety characteristics are identified by the symbol on
schematics or by special notes on the parts list. Use only replacement parts that
have critical characteristics recommended by the manufacturer.
2. Make leakage current or resistance measurements to determine that exposed
parts are acceptably insulated from the supply circuit before returning the unit
to the customer. Use the following checks to perform these measurements:
A. Leakage Current Hot Check-With the unit completely reassembled, plug
the AC line cord directly into a 120V AC outlet. (Do not use an isolation
transformer during this test.) Use a leakage current tester or a metering
system that complies with American National Standards Institute (ANSI)
C101.1 “Leakage Current for Appliances” and Underwriters Laboratories
(UL) 1492 (71). With the unit AC switch first in the ON position, then in the
OFF position, measure from a known earth ground (metal water pipe,
conduit, etc.) to all exposed metal parts of the unit (antennas, handle bracket,
metal cabinet, screwheads, metallic overlays, control shafts, etc.), especially
any exposed metal parts that offer an electrical return path to the chassis.
Any current measured must not exceed 0.5 milliamp. Reverse the unit power
cord plug in the outlet and repeat test. ANY MEASUREMENTS NOT WITHIN
THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCK HAZ ARD THAT MUST BE ELIMINATED BEFORE RETURNING THE UNIT TO
THE CUSTOMER.
B. Insulation Resistance Test Cold Check-(1) Unplug the power supply and
connect a jumper wire between the two prongs of the plug. (2) Turn on the
power switch of the unit. (3) Measure the resistance with an ohmmeter be-
tween the jumpered AC plug and each exposed metallic cabinet part on the
unit. When the exposed metallic part has a return path to the chassis, the
reading should be between 1 and 5.2 Megohms. When there is no return path
to the chassis, the reading must be “infinite”. If it is not within the limits specified,
there is the possibility of a shock hazard, and the unit must be repaired and re checked before it is returned to the customer.
3
ELECTROSTATIC DISCHARGE SENSITIVE (ESDS)
DEVICE HANDLING
This unit contains ESDS devices. We recommend the following precautions when repairing,
replacing or transporting ESDS devices:
• Perform work at an electrically grounded work station.
• Wear wrist straps that connect to the station or heel straps that connect to conductive floor
mats.
• Avoid touching the leads or contacts of ESDS devices or PC boards even if properly
grounded. Handle boards by the edges only.
• Transport or store ESDS devices in ESD protective bags, bins, or totes. Do not insert unprotected devices into materials such as plastic, polystyrene foam, clear plastic bags, bubble
wrap or plastic trays.
General Description
The 1801 and 1800 are Integral Design™ Power Amplifiers with all Silicon Solid-State Circuitry
using 14 power transistors per channel. Capable of complete stability with all loudspeaker
loads regardless of capacitive or inductive character. They employ fast acting electronic protection circuits for current limiting. They use computer grade capacitors throughout the power
supply, along with a 2.0kW power transformer and 1300 sq. inches of heat sink area. They also
have a power monitor display using a light emitting diode array and in the case of the 1801
signal meters as well.
CAUTION: THE BOSE® 1801/1800 POWER AMPLIFIERS CONTAIN NO USER-SERVICEABLE PARTS. TO PREVENT WARRANTY INFRACTIONS, REFER SERVICE TO WARRANTY SERVICE STATIONS OR FACTORY SERVICE.
4
DISASSEMBLY/ASSEMBLY PROCEDURES
1801 Power Amplifier
Note: Refer to Figure 1 for the following
procedures.
1. Top Cover Removal
4.3 Connect the wire harness, thermal
cutout wires, and the input cable to the
PCB.
5. Front Panel Removal
1.1 Remove the two screws that secure
the top cover at the rear of the unit. Loosen
the two screws located on each side of the
unit towards the front.
1.2 Slide the top cover towards the rear of
the unit and lift the cover off the unit.
2. Top Cover Replacement
2.1 Slide the top cover onto the unit while
making sure the screws on the side of the
unit are lining up with the slots in the top
cover.
2.2 Secure the top cover to the unit.
3. Amplifier PCB Removal
3.1 Perform procedure 1.
3.2 Disconnect the wire harness, the two
wires connected to the thermal cutout, and
the input cable going to the PCB.
5.1 Perform procedure 1.
5.2 Remove the nut securing the top of the
front panel. The nut is located on the inside
of the front chassis beside the thermal
cutout indicator.
5.3 Remove the knobs on the controls and
remove the two shaft nuts holding the front
panel in place.
6. Front Panel Replacement
6.1 Align the front panel over the controls
and secure it in place.
6.2 Secure the top of the front panel and
replace the knobs.
6.3 Perform procedure 2.
7. Front Chassis Assembly Removal
7.1 Perform procedure 5.
3.3 Remove the six screws (2B) located on
the side of the unit between the heat sink
fins (see Figure 2).
3.4 Carefully pry the PCB inward towards
the power transformer (the PCB is stuck to
the chassis by the heat sinking compound)
and lift the board out of the unit.
4. Amplifier PCB Replacement
4.1 Slide the PCB into place. Be sure there
is sufficient heat sink compound on the
PCB's heat sink.
4.2 Align the six screws that secure the
PCB into place and secure the PCB to the
chassis.
7.2 Locate and remove the four screws
that secure the front assembly to the
chassis.
7.3 Push down on the top of the front
assembly to release the bottom of the
assembly and pull the assembly towards
you.
8. Front Chassis Assembly Replacement
8.1 While pushing down on the front
assembly slide the assembly in towards the
unit.
8.2 Pull up on the front assembly to align
the screw holes with the unit and secure
the assembly in place.
8.3 Perform procedure 6.
5
DISASSEMBLY/ASSEMBLY PROCEDURES
1801 Power Amplifier
Note: Refer to Figure 5 for the following
procedures.
9. LED PCB Removal
12.2 Place the meter lamp housing over
the meters and secure it to the front assembly.
9.1 Perform procedure 7.
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. LED PCB Replacement
10.1 After reassembling the LED assem-
bly, place it onto the front panel assembly
and secure it in place.
10.2 Resolder the wires to the PCB.
12.3 Perform procedure 8.
13. Front Panel Controls Removal
13.1 Perform procedure 7.
13.2 Locate the control or switch you want
to replace and unsolder the wires and
components on that control or switch.
13.3 Remove the shaft nut holding the
control or switch to the front assembly and
remove it.
14. Front Panel Controls Replacement
14.1 Place the new control or switch into
the front assembly and secure it in place.
14.2 Resolder the wires and/ or components to the control or switch.
14.3 Perform procedure 8.
10.3 Perform procedure 8.
11. Meter Assembly Removal
11.1 Perform procedure 7.
11.2 Remove the three nuts holding the
meter lamp housing assembly to the front
panel assembly.
11.3 Remove the two nuts holding the
wires to the meter you want to replace and
remove the meter.
12. Meter Assembly Replacement
12.1 Place the new meter on to the front
assembly. Connect the wires going to the
meter.
15. Lamp Removal
15.1 Perform procedure 7.
15.2 Using a flat blade screwdriver, pry
under the edge of the socket and lift the
socket out.
16. Lamp Replacement
16.1 Replace the defective lamp.
16.2 Place the lamp socket back into the
lamp housing.
16.3 Perform procedure 8.
Note: It may be necessary to remove the
LED PCB Assembly to replace the lamps
see procedure 9.
6
DISASSEMBLY/ASSEMBLY PROCEDURES
1800 Power Amplifier
Note: Refer to Figure 1 for the following
procedures.
1. Top Cover Removal
1.1 Remove the four screws that secure
the top cover to the unit.
1.2 Slide the top cover towards the back of
the unit and lift it off.
2. Top Cover Replacement
2.1 Place the top cover on to the unit and
slide it under the front panel lip.
5. Front Panel Removal
5.1 Perform procedure 1.
5.2 Locate and remove the eight screws
holding the front panel to the chassis. Four
of the screws are located just inside the
two handles and the other four are the
larger screws on the front panel.
5.3 Using the handles pull the front panel
away from the chassis enough to access
the gain controls and LED PCB.
6. Front Panel Replacement
2.2 Secure the top cover to the unit.
3. Amplifier PCB Removal
3.1 Perform procedure 1.
3.2 Disconnect the wire harness, input
cable, and the two wires going to the
thermal cutout.
3.3 Remove the six screws (2B) located on
the side of the unit between the heat sink
fins (see Figure 2).
3.4 Carefully pry the PCB inward towards
the power transformer (the PCB is stuck to
the chassis by the heat sinking compound)
and lift the board out of the unit.
4. Amplifier PCB Replacement
4.1 Slide the PCB into place. Be sure there
is sufficient heat sinking compound on the
PCB's heat sink.
6.1 Slide the front panel into place. Be
careful not to pinch the wiring harness at
the bottom of the front panel between it
and the chassis.
6.2 Align the holes in the front panel with
the chassis, place the screws into their
location by hand and then tighten with a
screwdriver.
Note: While tightening the screws lift up
on the top lip of the panel to provide
enough room to slide the top cover under
the lip.
7. LED PCB Removal
7.1 Perform procedure 5.
7.2 Remove the two screws that secure
the PCB to the front panel.
7.3 Unsolder the wires at the LED PCB,
make a note of the wiring configuration,
and remove the board from the unit.
4.2 Align the six screws that secure the
PCB into place and secure the PCB to the
chassis.
4.3 Connect the wire harness, thermal
cutout wires, and the input cable to the
PCB.
8. LED PCB Replacement
8.1 Place the LED PCB into place on the
front panel.
8.2 Secure the PCB to the front panel.
8.3 Resolder the wires to the LED PCB.
7
DISASSEMBLY/ASSEMBLY PROCEDURES
1800 Power Amplifier
Note: Refer to Figures 3, and 4 for the
following procedures.
Note: Refer to Figure 6 for the following
procedures.
9. Gain Control Removal
9.1 Perform procedure 5.
9.2 Remove the gain control knobs.
9.3 Unsolder the capacitor lead and wires
from the control.
9.4 Remove the nut that secures the
control to the front panel and remove the
control.
10. Gain Control Replacement
10.1 Place the new control into the front
panel and secure it into place.
10.2 Resolder the capacitor lead and the
wires to the terminals on the gain control.
10.3 Perform procedure 6.
13. Rear Panel Removal
13.1 Perform procedure 1.
13.2 Locate and remove the four screws
securing the rear panel and the rear panel
bracket to the unit.
Note: One of the screws holds the ground
wires to the chassis. Take care not to lose
the nuts that secure this screw and the
wires.
14. Rear Panel Replacement
14.1 Align the rear panel with the chassis.
14.2 Secure the rear panel to the chassis.
Be sure to use the rear panel bracket on
the bottom of the panel.
14.3 Secure the ground wires to the
chassis.
11. Power Switch Removal
11.1 Perform procedure 5.
11.2 Remove the wires on the rear of the
power switch.
11.3 Remove the nut securing the switch
to the front panel and remove the switch.
12. Power Switch Replacement
12.1 Place the new power switch into the
front panel and secure it in place.
12.2 Reconnect the wires on the rear of
the switch.
12.3 Perform procedure 6.
14.4 Perform procedure 2.
8
TEST PROCEDURES
1. Bias Adjustment Setup and Procedure
1.1 Locate the -85V negative terminal
found on the capacitor (C4). See Figure 1
for the location of C4.
Note: The 1801 and very early 1800's had
two lugs on the caps. One with two or three
wires and one single wire. The later production 1800 had three lugs on the capacitor. Either way the lug with the two or three
wires is the lug to disconnect from the
capacitor. All other lugs remain.
1.2 Remove the lug with two or three wires
connected to it.
1.3 Connect a 0-200mA meter between
the disconnected lug and the - terminal on
the capacitor C4.
1.4 Disconnect the PCB that is not being
tested by unplugging the multiple pin
connector.
1.5 Turn the amplifier on with no input
signal applied and adjust the bias pot (R13)
for 90mA with the board cold.
Note: The PCB must be removed from
the chassis for the bias to be adjusted.
2. Frequency Response Procedure
2.1 Apply a 1Vrms, 1kHz signal to the
input.
4. Power Output Procedure
4.1 Connect an 8 ohm, 250 Watt load to
the output.
4.2 Apply a 1.75Vrms, 1kHz signal to the
input.
4.3 Turn the gain controls up to the point
where the clipping LED's just begin to
light up and check the output for 250
watts.
4.4 Repeat the steps above for a 4 ohm
load. The output measurement should be
400 watts.
5. Harmonic Distortion Procedure
5.1 With the unit connected as in proce-
dure 3, turn the gains up to just before
clipping and check the distortion at the
frequencies of 20Hz, 5kHz, and 10kHz.
5.2 The distortion limits are ≤.15% from
20Hz to 5kHz and ≤.5% from 5kHz to
10kHz.
6. Thermal Cutoff Procedure
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.
2.2 Reference a dB meter to the output.
2.3 Check the response from 20Hz to
20kHz. The response should not exceed ±1
dB. Refer to the response specification on
page 2.
3. DC Offset Procedure
3.1 With no signal applied measure the DC
offset at the output. It should measure
250mV or less.
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 the other channel and
short the output. Wait for the thermal
indicator to come on then remove the short
and cool the PCB.
9
Figure 1. 1801 Component Location
Figure 2. 1801 Side View
10
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