Bose FREESPACE BMA-125 User manual

1
Table of Contents
SAFETY INFORMATION ................................................................................................................... 2
Electrostatic Discharge Sensitive (ESDS) ..................................................................................... 3
120V Version Specifications ........................................................................................................ 4-5
230V Version Specifications ........................................................................................................... 6
120V Disassembly/Assembly Procedures ..................................................................................7-9
230V Disassembly/Assembly Procedures ..............................................................................10-12
BMA-125 Test Procedures 120V ..............................................................................................13-16
BMA 125 Test Procedures 230V.................................................................................................... 16
Part List Notes................................................................................................................................ 17
120V Main Assembly Part List ...................................................................................................... 18
Figure 1. 120V Chassis Layout...................................................................................................... 19
120V Amp PCB Part List ...........................................................................................................20-22
120V Tone/Volume Control PCB Part List............................................................................... 23-24
120V Equalizer PCB Part List................................................................................................... 25-26
230V Main Assembly Part list .................................................................................................. 27-28
230V Amp PCB Part List ...........................................................................................................29-31
230V Tone/Volume/Equalizer PCB Part List............................................................................32-35
Input Module 2B37 Part List.......................................................................................................... 36
Input Module 2B50 Part List.....................................................................................................37-38
Figure 2. 2B37 Schematic and PCB Layout................................................................................... 39
Figure 3. 2B50 Schematic and PCB Layout................................................................................... 40
Figure 4. 120V Driver PCB Layout................................................................................................. 41
Figure 5. 120V Tone/Volume Control PCB Layout ......................................................................... 41
Figure 6. 120V Equalizer PCB Layout (Solder Side) ..................................................................... 42
Figure 7. 120V Equalizer PCB Layout (Component Side) ............................................................. 42
Figure 8. 230V Driver PCB Layout................................................................................................. 43
Figure 9. 230V Tone/Volume/Equalizer PCB Layout .................................................................... 44
Figure 10. and 11. 230V wiring diagram ...................................................................................45-46

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
theAC 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 forAppliances" and Underwriters Laboratories
(UL) 1492 (71). With the unitAC switch first in the ON position and then in
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, screw heads, 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 milliampere. Reverse the unit power
cord plug in the outlet and repeat test. ANY MEASUREMENTS NOT WITHIN
THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCK HAZARD
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 between 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 poss-
ibility of a shock hazard, and the unit must be repaired and rechecked before it
is returned to the customer.

3
CAUTION: THE FREESPACE®BUSINESS MUSIC AMPLIFIER
CONTAINS NO USER-SERVICEABLE PARTS. TO PREVENT
WARRANTY INFRACTIONS, REFER SERVICING TO WARRANTY
SERVICE STATIONS OR FACTORY SERVICE.
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.
PROPRIETARY INFORMATION
THIS DOCUMENT CONTAINS PROPRIETARY INFORMATION OF
BOSE®CORPORATION WHICH IS BEING FURNISHED ONLY FOR
THE PURPOSE OF SERVICING THE IDENTIFIED BOSE PRODUCT
BYAN AUTHORIZED BOSE SERVICE CENTER OR OWNER OF THE
BOSE PRODUCT, AND SHALL NOT BE REPRODUCED OR USED
FOR ANY OTHER PURPOSE.

4
120V VERSION SPECIFICATIONS
Power Output 125W
Output Regulation Direct output: 0.5dB, no load to full load
Transformer outputs: 1.5dB, no load to full load
Input Sensitivity 2B37 dual input module
Input 1: Microphones: 1KΩ/350µV
Auxiliary: 10KΩ/100mV
Input 2: Microphones: 1KΩ/350µV
Auxiliary: 10KΩ/1V
Input 3 & 4: See instruction sheet enclosed with
module
Input 5: 10KΩ/100mV
Input 6: Mic Page: 150Ω/800µV
Output Impedance 70.7V 40Ω(transformer)
25V 5Ω(transformer)
31.65V 8Ω(transformer)
22.35V 4Ω(direct)
Functional Outputs EQ Out: 1.0V into 600Ω(post-master volume)
Line Out: 1.0V into 600Ω(post-master volume)
Tape Out: 650mV into 10KΩ(pre-master volume)
Mixer Output: 1.0V into 600Ω(pre-master volume)
Frequency Response
at 9dB below rated
output (EQ
bypassed)
EIA SE101A
Direct:
Transformer: 20Hz - 20KHz, ±1dB 20Hz - 20KHz, +1dB/-2dB
Power Bandwidth at
rated output/THD
(EQ bypassed)
Direct:
Transformer: 20Hz - 20KHz, ±1dB (1% THD) 50Hz - 20KHz, +1dB/-2dB (1% THD)
S/N Ratio All Controls left: 90dB
Input 5, Mic Page: 55dB
Modules-Low Z Mic: 60dB
Auxiliary: 70dB
Tone Controls Bass: ±3dB at 85Hz
Treble: ±3dB at 12.5KHz
Nominal Load Voltage

5
120V VERSION SPECIFICATIONS
(Continued)
Mute >30dB (Mute Input 3, 4, 5)
Control Interaction <1dB
Power Outlet Unswitched AC Outlet 120VAC 60HZ, 500W
AC Power
Consumption 120VAC, 60HZ at 3.0A at rated output (0.15A at idle)
Temperature Range 12°F to 140°F (-10°C to + 60°C)
Output Protection Electronic foldback and
thermal overload (both
self-restoring)
DC offset detection (for
direct coupled output)
Size 17"W x 12.75"D x 4.5"H (43.2 X 32.4 x
11.4 cm) (desk mount)
19"W x 12.75"D x 5.25"H (48.2 x 32.4 x
13.3 cm) (rack mount)
Weight 27lb (12.3 Kg)
Optional Modules 2B37 Dual input module Mic (screws)/Aux
2B50 Dual input module Mic (screws)/Stereo summing input (Aux)
2B42 Dual input module Aux/Telephone

6
Power Output 125W
Output Regulation Direct output: 0.5dB, no load to full load
Transformer outputs: 1.5dB, no load to full load
Input Sensitivity 2B37 dual input module
Input 1: Microphones: 200Ω/400mV
Input 2: Auxiliary: 10KΩ/1V
Input 3 & 4: See instruction sheet enclosed with module
Input 5: 10KΩ/100mV
Input 6: Mic Page: 150Ω/800µV
Output Impedance 100V 40Ω(transformer)
22.35V 4Ω(direct)
Functional Outputs EQ Out: 1.0V into 600Ω(post-master volume)
Line Out: 1.0V into 600Ω(post-master volume)
Tape Out: 650mV into 10KΩ(pre-master volume)
Mixer Output: 1.0V into 600Ω(pre-master volume)
Frequency Response at
9dB below rated output
(EQ bypassed)
EIA SE101A
Direct:
Transformer: 20Hz - 20KHz, ±1dB 20Hz - 20KHz, +1dB/-2dB
Power Bandwidth at
rated output/THD (EQ
bypassed)
Direct:
Transformer: 20Hz - 20KHz, ±1dB (1% THD) 50Hz - 20KHz, +1dB/-2dB (1% THD)
S/N Ratio All level Controls left: 90dB
Input 5, Mic Page: 55dB
Modules-Low Z Mic: 60dB
Auxiliary: 70dB
Tone Controls Bass: ±3dB at 85Hz
Treble: ±3dB at 12.5KHz
Mute >30dB (Mute Input 3, 4, 5)
Control Interaction <1dB
AC Power Consumption 230VAC, 50HZ at 1.6A at rated output (0.7A at
idle)
Temperature Range 12°F to 140°F (-10°C to + 60°C)
Output Protection Electronic foldback and
thermal overload (both self-
restoring)
DC offset detection (for
direct coupled output)
Size 17"W x 15"D x 5.75"H (43.2 X 38.1 x 14.6 cm)
(desk mount)
19"W x 15"D x 5.25"H (48.2 x 38.1 x 13.3 cm)
(rack mount)
Weight 25lb (11.3 Kg)
230V VERSION SPECIFICATIONS

7
120V DISASSEMBLY/ASSEMBLY PROCEDURES
1. Top Cover Removal
1.1 Remove the ten screws that secure the
top cover to the chassis. There are five on
each side.
1.2 Lift the cover up.
2. Top Cover Replacement
2.1 Place the top cover over the chassis
and align the five screw holes on the top
cover with the screw holes on the chassis.
2.2 Replace the ten screws that secure the
top cover to the chassis. There are five
screws on each side.
3. Input Module Removal
3.1 Remove the four screws that secure
the input module to the chassis.
3.2 Remove the input connector from the
input PCB.
3.3 Slide the input module out from the
rear of the chassis.
4. Input Module Replacement
4.1 Slide the Input Module into the rear of
the chassis so that the labels are aligned
with the labels on the chassis.
4.2 Replace the four screws that secure
the input module to the chassis.
4.3 Connect the input connector to the
input PCB.
5. Tone/Volume Control PCB Removal
5.1 Remove the two screws from the
bottom of the chassis that secure the PCB
to the chassis.
5.2 Remove the input Five, bass and treble
control knobs by pulling straight away on
them.
5.3 Remove the three nuts that secure the
input Five, bass and treble controls to the
chassis.
5.4 Slide the PCB towards the rear of the
unit until the potentiometer's shafts clear
the holes in the chassis.
5.5 Lift the PCB up.
5.6 Remove the four screws that secure the
shield to the PCB.
5.7 Remove all wires attached to the PCB.
Note: Make a note of the wiring configura-
tion before removing any wires.
6. Tone/Volume Control PCB Replace-
ment
6.1 Attach the wires to the PCB.
6.2 Replace the four screws that secure
the shield to the PCB.
6.3 Lower the PCB into the chassis and
slide it forward until the shafts protrude out
the front of the chassis.
6.4 Replace the three nuts that secure the
input five, bass and treble control potenti-
ometer to the chassis.
6.5 Replace the control shaft knobs by
pushing them on.
6.6 Replace the two screws located on the
bottom of the chassis that secure the PCB
to the chassis.
7. Input 1, 2, 3, 4 and Master Volume
Control Removal
7.1 Pull out on the knob to remove it.
7.2 Remove the nut that secures the pot's
shaft to the chassis.
7.3 Slide the pot out of the hole in the
chassis.

8
120V DISASSEMBLY/ASSEMBLY PROCEDURES
7.4 Remove all the wires from the pot.
Note: Make note of the wiring configura-
tion.
8. Input 1, 2, 3, 4 and Master Volume
Control Replacement.
8.1 Attach the wires to the pot.
8.2 Insert the pot's shaft into the hole in
the chassis.
8.3 Replace the nut that secures the pot's
shaft to the chassis.
8.4 Replace the control knobs by pushing
them onto the pot's shaft.
9 Driver PCB Removal
9.1 Remove the four screws that secure
the Driver PCB to the chassis.
9.2 Remove all the connectors and wires
from the PCB.
Note: Make note of the wiring configura-
tion.
9.3 Lift the Driver PCB up.
10. Driver PCB replacement
10.1 Lower the PCB into the chassis so
that the two large capacitors are located
toward the transformer. Align the screw
holes in the PCB with the standoffs on the
chassis.
10.2 Replace the four screws that secure
the driver PCB to the chassis.
10.3 Replace all the wires and connectors
to the driver PCB.
11. Equalizer PCB Removal
11.1 Remove the connector from the
equalizer PCB.
13.3 Remove the four screws and nuts that
secure the transformer bracket to the
transformer.
14. Speaker Output Transformer Replace-
ment.
14.1 Replace the four screws and nuts that
secure the transformer bracket to the
transformer.
14.2 Lower the transformer into the chas-
sis and align the transformer so that the
purple and brown wires face towards the
rear of the chassis.
14.3 Replace the four screws that secure
the transformer bracket to the chassis.
14.4 Replace the transformer's wires to the
speaker output terminals and the driver
PCB.
13. Speaker Output Transformer Removal
13.1 Remove all the wires that connect the
transformer to the speaker output terminals
and the driver PCB.
Note: Make a note of the wiring configura-
tion.
13.2 Remove the four nuts that secure the
transformer bracket to the chassis.
12. Equalizer PCB Replacement
12.1 Lower the equalizer PCB into the
chassis.
12.2 Replace the two screws that secure it
to the chassis.
12.3 Connect the connector to the PCB.
11.2 Remove the two screws that secure
the equalizer to the chassis.
11.3 Lift the equalizer PCB up.

9
120V DISASSEMBLY/ASSEMBLY PROCEDURES
15. Power Transformer Removal
15.1 Remove the wires that connect to the
AC outlet, power switch and driver PCB.
Note: Make note of the wiring configura-
tion.
15.2 Remove the four nuts that secure the
transformer bracket to the chassis.
15.3 Remove the four screws and nuts that
secure the transformer bracket to the
transformer.
16. Power Transformer Replacement
16.1 Replace the four screws and nuts that
secure the transformer bracket to the
transformer.
16.2 Lower the transformer into the chas-
sis and align the transformer so that the
wires face towards the inside of the unit.
16.3 Replace the four screws that secure
the transformer bracket to the chassis.
16.4 Replace the wires that connect to the
AC outlet, power switch and driver PCB.
17. Output Transistor and Heat sink
Removal
18.1 Remove the four screws that secure
the heat sink to the chassis.
18.2 Lift the heat sink up.
18.3 Remove the two screws that secure
the transistor to the heat sink.
18.4 With a pair of pliers, grab onto the
transistor and pull it out of the transistor
socket.
19. Output Transistor and Heat sink
Replacement.
19.1 Push the transistor into the transistor
socket.
Note: Inspect the mylar insulator for
damage. Replace if necessary. Make sure
the transistor and the transistor socket are
flush with the heat sink.
19.2 Replace the two screws that secure
the transistor to the heat sink.
19.3 Lower the heat sink into the chassis
so that the screws holes in the heat sink
align with the screw holes in the chassis.
19.4 Replace the four screws that secure
the heat sink to the chassis.

10
230V DISASSEMBLY/ASSEMBLY PROCEDURES
1. Top Cover Removal
1.1 Remove the fourteen screws that
secure the top cover to the chassis. There
are seven on each side.
1.2 Slide the top cover toward the rear of
the unit and then lift it up.
2. Top Cover Replacement
2.1 Lower the top cover onto the chassis
and slide it toward the front of the unit.
2.2 Replace the fourteen screws that
secure the top cover to the chassis. There
are seven screws on each side.
3. Input Module Removal
3.1 Remove the four screws that secure
the input module to the chassis.
3.2 Remove the input connector from the
input PCB.
3.3 Slide the input module out from the
rear of the chassis.
4. Input Module Replacement
4.1 Slide the input module into the rear of
the chassis so that the labels are aligned
with the labels on the chassis.
4.2 Replace the four screws that secure
the input module to the chassis.
4.3 Attach the input connector to the input
PCB.
5. Tone/Volume/Equalizer PCB Removal
5.1 Remove the input five, bass and treble
control knobs by pulling them straight away
from the unit.
5.2 Remove the three nuts that secure the
input five, bass and treble controls to the
chassis.
5.3 Remove the two nuts that secure the
PCB shield to the chassis.
5.4 Slide the PCB towards the rear of the
unit until the potentiometer shafts clear the
holes in the chassis.
5.5 Lift the PCB up.
5.6 Remove the four screws that secure
the shield to the PCB.
5.7 Remove the connectors from the PCB.
6. Tone/Volume/Equalizer PCB Replace-
ment
6.1 Attach the connectors to the PCB.
6.2 Replace the four screws that secure
the shield to the PCB.
6.3 Lower the PCB into the chassis and
slide it towards the front of the unit until the
shafts protrude out the front of the chassis.
6.4 Replace the three nuts that secure the
input five, bass and treble control pots to
the chassis.
6.5 Replace the control shaft knobs by
pushing them on.
6.6 Replace the two nuts that secure the
PCB shield to the chassis.
7. Input 1, 2, 3, 4 and Master Volume
Control Removal
7.1 Pull on the control knob to remove it.
7.2 Remove the nut that secures the pot's
shaft to the chassis.
7.3 Slide the pot out of the hole in the
chassis.
7.4 Remove all wires from the pot.
Note: Make note of the wiring configura-
tion.

11
8. Input 1, 2, 3, 4 and Master Volume
Control Replacement
8.1 Attach the wires to the pot.
8.2 Insert the pot's shaft into the hole in
the chassis.
8.3 Replace the nut that secures the pot's
shaft to the chassis.
8.4 Replace the control knobs by pushing
them onto the pot's shaft.
9. Driver PCB Removal
9.1 Remove the seven screws that secure
the driver PCB to the chassis. One screw is
located just below and between the two
large capacitors.
9.2 Remove the connectors and the wires
from the PCB.
Note: Make note of the wiring configura-
tion.
9.3 Lift the driver PCB up.
10. Driver PCB replacement
10.1 Lower the PCB into the chassis so
that the two large capacitors are located
towards the front of the unit. Align the
screw holes in the PCB to the holes in the
chassis.
10.2 Replace the seven screws that
secure the driver PCB to the chassis.
10.3 Replace the wires and connectors to
the driver PCB.
11. Speaker Output Transformer Removal
11.1 Remove all the wires that connect the
transformer to the driver PCB and the
speaker output terminals.
11.2 Remove the four screws that secure
the transformer to the chassis.
12. Speaker Output Transformer Replace-
ment
12.1 Lower the transformer into the chas-
sis so that the wires face toward the rear of
the unit.
12.2 Replace the four screws that secure
the transformer to the chassis.
12.3 Attach the wires to the driver PCB
and the speaker output terminals.
13. Power Transformer Removal
13.1 Remove the wires that connect to the
driver PCB, chassis terminal and the power
switch.
13.2 Remove the four nuts that secure the
transformer bracket to the chassis. Two of
the nuts are located on the bottom of the
chassis and two are located on the side of
the chassis.
13.4 Lift the transformer up.
13.5 Remove the Four screws that secure
the transformer to the transformer bracket.
14. Power Transformer Replacement
14.1 Replace the four screws that secure
the transformer bracket to the transformer.
14.2 Lower the transformer into the chas-
sis so that the black and blue wires face
toward the driver PCB.
14.3 Replace the four nuts that secure the
transformer bracket to the chassis.
14.4 Attach the wires to the driver PCB,
chassis terminal and the power trans-
former.
230V DISASSEMBLY/ASSEMBLY PROCEDURES

12
15. Output Transistor and Heat Sink
Removal
15.1 Remove the two nuts that secure the
heat sinks to the chassis.
15.2 Lift the heat sink up.
15.3 Remove the two screws that secure
the transistor to the heat sink.
15.4 With a pair of pliers, grab onto the
transistor and pull it out of the transistor
socket.
16. Output Transistor and Heat Sink
Replacement
16.1 Push the transistor into the transistor
socket.
Note: Inspect the mylar insulator for
damage. Replace if necessary. Make sure
the transistor and the transistor socket is
flush with the heat sink.
16.2 Replace the two screws that secure
the transistor to the heat sink.
16.3 Lower the heat sink into the chassis
so that the screw holes in the heat sink
align with the screws in the chassis.
16.4 Replace the two screws that secure
the heat sink to the chassis.
17. Fuse replacement
17.1 Use a flat blade screw driver to pry off
the fuse holder located on the AC recep-
tacle.
17.2 Pull the card out to expose the fuse.
Lift the fuse out and replace it with a fuse of
equal value. See the part list for the part
number.
230V DISASSEMBLY/ASSEMBLY PROCEDURES
12

13
BMA-125 120V Test Procedures
General Test Setup
Connect a 4Ω, 5Ω, 8Ωand 40Ω200W load
to the 4, 5, 8, and 40Ωoutputs respectively.
Disconnect J1 (located at the equalizer
PCB) and add a jumper from pin 1 (yellow)
to pin 3 (violet) of the J1 connector. This
will bypass the internal equalizer.
Set the tone controls to the center (flat)
position unless otherwise noted.
1. Controls
1.1 Adjust Input Five to the full clockwise
position. Adjust the tone controls to their
center (flat) position and all other volume
controls to their full counter clockwise
position.
1.2 Apply a 100mVrms, 1KHz signal to
Input Five.
1.3 Using the Master volume control,
adjust the output across the 4Ωload to
1Vrms. Reference a dB meter to the
output.
1.4 Apply a 100mVrms, 85 Hz signal to
Input Five. Rotate the bass control to the
full counter clockwise position. Measure the
output. It should be -3 dB ±1dB.
1.5 Rotate the bass control to the full
clockwise position. Measure the output. It
should be 3 dB ±1dB.
1.6 Apply a 100mVrms, 10KHz signal to
Input Five. Rotate the treble control to the
full counter clockwise position. Measure the
output. It should be -3.5 dB ±1 dB.
1.7 Rotate the treble control to the full
clockwise position. Measure the output. It
should be 3.2 dB ±1 dB.
2. 4ΩOutput
Note: Remove the “4Ω” to “PRI” jumper.
Connect a 4Ωload between “COM” and
“4Ω”.
2.1 Apply a 105Vrms, 1KHz signal to Input
Five. Adjust Input Five to full output at the
4Ωoutput (just before clipping).
2.2 Measure the voltage at the output. It
should be ≥24Vrms.
2.3 Measure the distortion. It should be
< 0.5%.
2.4 With the 4Ωoutput adjusted to
24Vrms, reference a dB meter to the
output.
Measure the response according to the
following table.
Frequency Output
(dB) Tolerence (dB)
20 Hz 0 -2
1 KHz ref -
20 KHz 0 -1.5
3. 8ΩOutput
Note: Place a jumper between the output
connector labeled “4Ω” and the output
connector labeled “PRI”. Connect an 8Ω
load to the 8Ωoutput and the terminal
marked lo.
3.1 Apply a 120 mVrms, 1KHz signal to
Input Five.Adjust Input Five to full output at
the 8Ωoutput (just before clipping).
3.2 Measure the voltage at the 8Ωoutput.
It should be ≥32Vrms.
3.3 Measure the distortion. It should be
< 0.5%.
3.4 With the 8Ωoutput adjusted to
31 Vrms, reference a dB meter to the
output. Measure the response according to
the following table.

14
Frequency Output
(dB) Tolerence (dB)
50Hz 0 -2
1KHz ref -
20KHz 0 -2.8
3.5 Adjust Input Five until 11.2Vrms is
measured across the 8Ωload. Reference a
dB meter to the output.
3.6 Measure the response according to the
following table.
Frquency Output
(dB) Tolerence (dB)
20Hz 0 -2
1KHz ref -
20KHz 0 -2.5
4. 25 Volt Output
Note: Place a jumper between the output
connector labeled “4Ω” and the output
connector labeled “PRI”. Connect a 5Ω
load to the 25V output and the terminal
marked lo.
4.1 Apply a 120mVrms, 1KHz signal to
Input Five. Adjust Input Five to full output
at the 25V output (just before clipping).
4.2 Measure the output. It should be
≥25Vrms.
4.3 Measure the distortion. It should be
< .5%.
4.4 With the 25V output adjusted to
25Vrms, reference a dB meter to the
output. Measure the response according to
the following table.
Frequency Output
(dB) Tolerence (dB)
50Hz 0 -2
1KHz ref -
20KHz 0 -2.5
4.5 Adjust Input Five until 8.875 Vrms is
measured across the 8Ωload. Reference a
dB meter to the output.
4.6 Measure the response according to the
following table.
Frequency Output
(dB) Tolerence (dB)
20Hz 0 -2
1KHz ref -
20KHz - -2.5
5. 70 Volt Output
Note: Place a jumper between the output
connector labeled “4Ω” and the output
connector labeled “PRI”. Connect a 40Ω
load to the 70V output and the terminal
marked lo.
5.1 Apply a 105mVrms, 1KHz signal to
Input Five. Adjust Input Five to full output at
the 70 Volt output (just before clipping).
5.2 Measure the output. It should be
≥70.7 Vrms.
5.3 Measure the distortion. It should be
< .5%.
5.4 With the output adjusted to 70.7Vrms,
reference a dB meter to the output. Mea-
sure the response according to the follow-
ing table.
Frequency Output
(dB) Tolerence (dB)
50Hz 0 -2
1KHz ref -
20KHz 0 -2.5
6. Tape Output
6.1 Apply a 100mV, 1KHz signal to Input
Five.
6.2 Adjust Input Five to the full clockwise
position.
BMA-125 120V Test Procedures

15
7. Mixer Output
7.1 Apply a 100mVrms, 1KHz signal to
Input Five.
7.2 Adjust Input Five to the full clockwise
position.
7.3 Measure the Mixer Output. It should be
1Vrms (-.2, +.29).
8. Line Output
8.1 Apply a 100mVrms, 1KHz signal to
Input Five.
8.2 Adjust Input Five to the full clockwise
position.
8.3 Measure the line output. It should be
.93Vrms (-.19, +.17).
9. Master Volume Control Range
9.1 Apply a 105mVrms, 1KHz signal to
Input Five.Adjust the Master volume
control to the full clockwise position. Adjust
Input Five to full output (just before clip-
ping).
9.2 Reference a dB meter to the 4Ω
output.
9.3 Rotate the Master volume control to
the full counter clockwise position.
9.4 Measure the 4Ωoutput. It should be
≤-50 dB.
10.4 Measure the 4Ωoutput. It should be
≤- 70dB.
11. Input 1 and 2: 400µV Microphone
Input
11.1 Apply a 400µVrms, 1KHz signal to
Input 1 or 2. Move the selector switch to
the Mic setting.
11.2 Reference a dB meter to the applied
signal.
11.3 Measure the Line Output. It should be
67 dB ±1 dB.
11.4 Reference a dB meter to the Line
Output.
11.5 Change the input signal to 20Hz. With
the Mic EQ switch in the FLAT setting,
measure the Line Output. It should be
-5.3 dB ±2 dB. With the Mic EQ switch in
the LOCUT setting, it should be -24.8 dB
±4 dB.
11.6 Change the input signal to 20KHz.
With the Mic EQ switch in the FLAT setting,
measure the Line Output. It should be
-1 dB ±1 dB. With the Mic EQ switch in
the LOCUT setting, it should be -1 dB
±1 dB.
11.7 Apply a 100mV, 1KHz signal to the
INPUT 1 RCAjack or 1Vrms, 1KHz to
INPUT 2.
11.8 Move the selector switch to the AUX
setting. The LINE output should be clean.
Note: Perform the AUX test on both
channels for the 220V variation.
10. Mute Control Attenuation
10.1 Apply a 105mVrms, 1KHz signal to
Input Five. Adjust the Master volume
control to the full clockwise position. Adjust
Input Five to full output (just before clip-
ping).
10.2 Reference a dB meter to the 4Ω
output.
10.3 Short the two screws labeled mute
together.
6.3 Measure the Tape Output. It should be
1Vrms ( -.21, +.26).
BMA-125 120V Test Procedures

16
BMA-125 120V Test Procedures
12. Input 3, 4
12.1 Perform the test procedure 11, if the
optional input module is installed.
13. MIC PAGE INPUT
13.1 Apply a 800µVrms, 1KHz signal to
the MIC PAGE INPUT. Rotate the PAGE
LEVEL pot to the full clockwise position.
13.2 Reference a dB meter to the applied
signal.
13.3 Measure the LINE output. It should be
60 dB ±4 dB.
14. Model 8, 32 EQ
Note: Connect J1 to the EQ PCB. This will
insert the internal EQ. Do this if J1 was
disconnected according to the general test
setup procedure.
14.1 Apply a 100mVrms, 1KHz signal to
Input Five. Move the EQ selector switch to
the Model 8 position.
14.2 Adjust the Master and Input Five gain
controls to obtain a 5Vrms output from the
4Ωoutput.
14.3 Reference a dB meter to the 4Ω
output. Measure the response according to
the following table.
Frequency Output
(dB) Tolerence (dB)
20Hz -20.3 ±3
85Hz 13.2 ±1.5
250Hz 3.7 ±1.5
500Hz .9 ±1.5
1KHz ref -
5KHz 5.8 ±1.5
12.5KHz 12.4 +.85,-2.15
20KHz 2.1 ±3
14.4 Move the EQ selector switch to the
Model 32 position. Measure the response
according to the following table.
230V Variation Tests
Note: Perform all the proceeding tests
except 3, 4 and 5.
1. Remote Master Volume
1.1 Apply a 100mV, 1KHz signal to Input
Five.
1.2 Connect a 4Ωload to the 4Ωoutput.
1.3 Adjust Input Five and the Master
volume control so that 24Vrms is measured
across the 4Ωload.
1.4 Reference a dB meter to the 4Ω
output.
1.5 Connect a 10KΩpot to the terminals
marked Remote Master. Rotate the pot to
its minimum resistance position. Measure
the 4Ωoutput. It should be ≤-40dB.
2. 100V Output
Note: Remove the 4Ωto PRI jumper and
connect a 80Ωload to the 100V output.
2.1 Apply a 100mVrms, 1KHz signal to the
100V output.
2.2 Adjust Input Five to the full clockwise
position. Adjust the Master volume control
so that 100Vrms is measured across the
80Ωload. The signal should look clean.
Frequency Output (dB) Tolerence (dB)
20Hz -18.4 ±3
85Hz 14.5 ±1.5
250Hz 4.3 ±1.5
500Hz 1.2 ±1.5
1KHz ref -
5KHz 9.2 ±1.5
12.5KHz 15.5 +.8, -2.2
20KHz 5.4 ±3

17
PART LIST NOTES
1. This part is not normally available from Customer Service. Approval from the Field
Service Manager is required before ordering.
2. The individual parts located on the PCB are listed in the electrical part list.
3. !This part is critical for safety purposes. Failure to use a substitute replacement
with the same safety characteristics as the recommended replacement part might create
shock, fire and/ or other hazards.

18
120V Main Assembly Part List
(Figure 1)
Reference
Designator Description Part Number Qty See Note
Q101, 103 Transistor (MJ 15022) 185231 2
Q102, 104 Transistor (MJ 15023) 185232 2
S101-S104 Socket, transistor, W/TO-3CA 185310 4
S101-S104 Insulator, Wafer 183311 4
T101 Power Transformer (T101) 185229 1 3
T102 Output Transformer (T102) 185230 1 3
R101-104 Pot 5K LIN PNL 185247 4
R100, 105 Pot 5K LIN PNL ADJ 185285 2
C101 Cap 220µF 100V 20% 185241 1
Cap 3300 Pf 1400V CER 185242 1 3
F101 Fuse 4A 250V SLO BLO 185245 1 3
S101 Power Switch 185271 1 3
Power Cord 185233 1
Bracket Heatsink Mtg 185234 4
Bracket Transformer 185235 1
Driver PCB 185236 1 1, 2
Tone/Volume PCB 185237 1 1, 2
Equalizer PCB 185239 1 1, 2
Heatsink 185240 1
Knob, Small 185243 7
Knob, Large 185244 1
Fuseholder 185246 3
Top Cover 185272 1
Terminal Strip, Barrier, 7Ckt 185273 1
Transistor Socket 185274 4
Connector, housing, 6 Ckt 185275 1
Foot 185276 4
2B50 Dual input module-Mic
(screws)/Stereo summing input
(AUX)
180139-2B50 2
2B37 Dual input module-Mic
(screws)/AUX 180140-2B37 2
!
!
!
!
!
!
!

19
Figure 1. 120V Chassis Layout
T101 POWER TRANSFORMER
T102 AUDIO
TONE/VOLUME PCB
DRIVER PCB
INPUT MODULE INPUT
MODULE
C101
Q101, 103
Q102, 104
S101 POWER
R100 MASTER
TREBLE BASS
INPUT 5 INPUT 4 INPUT 3 INPUT 2 INPUT 1
R27 R22 R7 R104 R103 R102 R101
F101 EQUALIZER
SWITCH
R105 PAGE LEVEL
EQUALIZER PCB

20
Reference
Designator Description Part Number See Note
R1 5.1Ω, 5%, 1/4W,
CF 185286
R2, 41 10KΩ, 5%, 1/4W,
CF 185433
R4 47KΩ, 5%, 1/4W,
CF 185316
R5 POT, 100KΩ, LIN
FLAT PCB 185317
R6 51KΩ, 5%, 1/4W,
CF 185318
R7 750Ω, 5%, 1/4W,
CF 185319
R8 680Ω, 5%, 1/4W,
CF 185320
R9 470Ω, 5%, 5W 185321
R10, 11 10Ω, 5%, 1/4W,
CF 185322
R12 2.4KΩ, 5%, 1/4W,
CF 185323
R13 6.8KΩ, 5%, 1/4W,
CF 185324
R14 180KΩ, 5%,1/4W,
CF 185325
R15, 40 5.1KΩ, 5%, 1/4W,
CF 185326
R16 1.5Ω, 5%, 1/4W,
CF 185327
R17 150Ω, 5%, 1/4W,
CF 185328
R18, 21, 22, 26,
27, 30 100Ω, 5%, 1/4W, CF 185329
R19 3.9Ω, 5%, 5W 185330
R20 POT, 200Ω, LIN
FLAT PCB 185331
R23 620Ω, 5%, 5W 185332
R24, 29, 36 1.0KΩ, 5%, 1/4W,
CF 185442
R25, 28, 46, 47 120Ω, 5%, 1/4W,
CF 185334
R31-34 .22Ω, 5%, 5W 185335
R35 360Ω, 5%, 2W 185336
R37 43KΩ, 5%, 1/4W,
CF 185337
120V AMP PCB
Resistors