MURA BM54 User manual

1
BM54 AMP Repair kit
1.Overview
Thank you for purchasing BM54 repair kit.
Along with this guide it should help you retain sound on all channels on BM54 radios suffering poweramp failure which is
common to this type of module. Upon completion you’ll have a fully functional BM54 with no recurring problem and
same or better sound than stock power amplifier. The poweramp IC used in this kit has better electrical characteristics,
and is better protected against short circuit, over temperature and overvoltage. It has better supply filtering and as the
stock model has an output pin for clipping detection (distortion).
2. Package contents
Your kit should contain the following:
-Amp PCB 4x40w audio amp with standby/clip detector control complete with components soldered
-connecting wires (output wires, input coax cables, supply
-Two screws with nuts/washers
-this guide
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

2
3.Mounting /installation instructions
3.1 Disassembly
Open top cover
Remove screws (1)
Remove screws (2)
Remove clip (3)
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

3
Remove main BM54 PCB from housing.
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

4
3.2 Preliminary work with the board
Cut traces as indicated below. This way you isolate old poweramps from the circuit.
You should obtain something like this:
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

5
3.3 Connection points
BM54 Poweramp kit connection points.
(indicated in red)
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

6
BM54 main PCB connection/soldering points
Input connections, standby/mute signal:
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

7
Output (Speaker) connections:
You can use two locations for connecting speaker outputs to BM54 board.
1.
2. Also showing power supply soldering points.
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

8
Clip detector soldering point.
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

9
Use the corresponding cables and solder them into place
Now connect each wire to corresponding Poweramp board socket. Don’t forget
to check for correct polarity/signals wiring between the two PCBs.
Next you have to drill 2 holes in BM54 chasis so you can mount poweramp board
using the screws/nuts supplied. After that, mount main BM54 PCB into chasis
and mount retaining clip (3) to slightly fix the board into place. Continue with
fixing the powerIC on the chasis.
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

10
Warning:
-Don’t let the washers touch ic terminals
-use a non-conducting spacer between amp PCB and bm54 tuner metallic shield.
-Be sure to use a spacer between poweramp board and BM54 metallic RF shield
beneath. Neglecting that you might get shorts between terminals and metallic RF
shield resulting in catastrophic failure.
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

11
4. Signal description
Supply:
VCC=supply voltage for poweramp circuit
GND=ground
Outputs/speakers
RR+ rear right speaker output positive activation
RR- rear right speaker output negative activation
FR+ front right speaker output positive activation
FR- front right speaker output negative activation
RL+ rear left speaker output positive activation
RL- rear left speaker output negative activation
FL+ front right speaker output positive activation
FL- front right speaker output negative activation
Input signals
RRin+ input signal for rear right channel
FRin+ input signal for front right channel
RLin+ input signal for rear left channel
FLin+ input signal for front left channel
All 4 input signals have common GND.
Other signals
STB_mute –standby/mute connection (RED wire already soldered on poweramp board)
CD –clip detector connection (BLUE wire already soldered on poweramp board)
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

12
WARNING:
Some people used to isolate the old poweramps cutting the traces right after the main speaker connector on the small
daughter PCB. By doing that you risk cutting other traces you don’t want to because that PCB is multilayered with 4
layers. You’ll further damage your module if you’re doing that. Other mistake is to remove the old epoxied poweramps
with back-plate which additionally to heat transfer it acts like a spacer between main PCB and BM54 chasis. If you
remove the chips and don’t retain the spacers you’ll risk to shortcircuit your whole module rendering it unusable and
possible unserviceable.
Below are some pictures reflecting wrong installations:
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]

13
Mura Car Accessories (MCA)
Str Doctor Iacob Felix, et 1, apt 1 011031,
Bucuresti, sector 1
T: ([phone] | ([phone]
W: https://mca.electricmura.ro/ro
E: [email protected]