JBL Professional MPC-XU User Manual

2

II. Installation

CAUTION: The MPC-XU contains active components which can be damaged by electro-

static discharge (ESD). Be sure to practice standard ESD precautions, and always ground

yourself and your workstation before handling exposed circuit cards.
Installing the MPC-XU requires PC board soldering skills. Only qualified service technicians

should attempt it. Any authorized JBL service center can perform the installation.
The MPC-XU installs on the amplifier input board of any JBL MPA or MPC amplifier.

Tools needed:

Soldering iron
¼-inch (6.3 mm) nutdriver
Phillips screwdriver
Wire cutters
Rosin-core solder
Desoldering iron or other suitable desoldering equipment (Do not use desoldering braid; it can

damage the solder pads on the input board and might not remove solder adequately.)

CAUTION: Preparing the input board for installation of the MPC-XU involves removing

solder from feed-through holes on a 2-sided circuit board. Excessive heat can damage the

solder pads you will be working on. Proper equipment and experience with desoldering

delicate PC board circuitry is essential to successfully perform the procedure. Damage caused

by improper installation is not covered under warranty.
1 Turn off  the amplifier and disconnect the AC power cord from the AC source. Disconnect

all cables from the amplifier’s input panel.

2 Position the amplifier so the rear of  the chassis is facing you. The input panel is located on

the left side of the rear panel. See Figure 2a.

CH1

CH2

CH1

CH2

BRIDGE

MONO

BRIDGE

MONO

LOW  IMPEDANCE

LOW  IMPEDANCE

DIR.  OUTPUT

DIR.  OUTPUT

ISOL.OUTPUT

ISOL.OUTPUT

AUDIO  TRANSFORMER

AUDIO  TRANSFORMER

70V

70V

25V

25V

100V

100V

0 70 100

0 70 100

0

0

-dB

-dB

10

10

8

8

6

6

4

4

2

2

24

24

18

18

14

14

STEREO

12

12

CH2    INPUT    CH1

CH2                                                                                                                                                  CH1

PARALLEL        BRIDGE

LEVEL

LEVEL

GROUND

INPUT

3 Locate and remove the screws securing both the upper blank and the lower input panels to

the rear side of  the chassis (2 screws on each mini panel). The upper blank panel will

simply drop off  when its screws are removed.

4 Gently pull the lower input panel out from the amplifier. Once it is removed, you will

notice a ribbon cable connecting the input PC board to the amplifier. Disengage the

locking wing clamps on the ribbon header and carefully remove the ribbon head from the

socket on the board. Now the input panel assembly is completely free from the amplifier.

5 Desolder and remove the wire jumper pairs indicated in Figure 2b or 2c.
6 Under where the jumpers were located, you’ll find two rows of  solder pad holes—one

with 10 holes and another with 12 holes. Remove the solder from all 22 holes.

7 With the input panel facing you and the component side of  the MPC-XU board facing

away from you, carefully insert the header pins of the MPC-XU fully into the socket holes.

Turn the assembly over and solder the MPC-XU in place. Make sure all the header pins are

well soldered. Visually inspect for cold solder joints and verify that you have sufficient

clearance to re-install the ribbon connector on the top side of the assembly. Finish by

trimming the MPC-XU header pins as required.