Introduction; Service Bulletins; The Well-Equipped Service Bench; Working With Surface-Mount Components - QSC PowerLight Series Technical & Service Manual

1. Introduction

1.1 Service bulletins

Contact QSC Technical Services to make sure you have the most
up-to-date service bulletins for PowerLight Series amplifiers.
Service bulletins may be distributed in hard copy, via fax, and
electronically (Adobe Acrobat PDF) via CD-ROMs, FTP from the QSC
web site (www.qscaudio.com), and e-mail.
These service bulletins had been issued at the time this manual
was printed: PFC0001, "PFC MOSFET Replacement" (PowerLight
PFC PFC
6.0 and PowerLight 9.0 only); PFC0002, "PFC Power Supply
Replacement Guidelines" (PowerLight 6.0
only); and PFC0003, "Amplifier Goes Into Protect When Turned On"
(all three models).
1.2 The well-equipped service
bench
To properly service QSC amplifiers, a technician needs the right
tools. The technician's service bench should have the following
equipment:
• Digital multimeter with RMS AC voltage and current
• Digital clamp-on ammeter
• Dual-trace oscilloscope
• Audio distortion analyzer
• Non-inductive load resistors, configurable as 8 ohms (min. 1800
watts capacity), as 4 ohms (min. 3200 watts capacity), and as
2 ohms (min. 4500 watts capacity)
• Variable AC voltage source, such as a Variac or Powerstat
variable transformer, with a rated current capacity of up to 50A
(for 120V models) or 25A (for 230V models)
• Low-distortion audio sine wave generator
• Philips and flat screwdrivers
• Soldering iron with a fine tip (25–60W recommended)
• Rosin-core solder (60/40 or 63/37)
• Long-nose pliers
• Diagonal cutters
• Wire strippers
Automated test equipment, such as an Audio Precision worksta-
tion, is very useful for servicing PowerLight amplifiers. Contact
QSC Technical Services to obtain applicable AP test files.
Servicing power supply modules will require some additional
special-built equipment:
• Power supply remote controller
• PFC power supply fixture (for PFC modules only)
• CMP box
Becauseof the complexity of the PFC power supplies, QSC
recommends they be serviced only by QSC.
Technical Service Manual
PowerLight 6.0 II, PowerLight 6.0
PFC and PowerLight 9.0
PFC , and PowerLight 9.0 PFC
1.3 Working with surface-mount
components
PowerLight amplifiers, like many modern electronic products, use
surface-mount technology (SMT) components where appropriate in
order to make high-density circuitry that is reliable and economical
to manufacture.
SMT components in the PowerLight amps are used in the small-
signal and control circuits, so they do not handle significant
amounts of power; therefore, they are subject to very little stress
PFC
and should seldom fail. Sometimes they do fail, or they require
replacement for a performance upgrade or modification. Thus, it is
important to know how to work with SMT components.
Specialized tools and equipment exist for soldering, unsoldering,
and removing SMT components quickly and efficiently, but they are
often expensive. Most SMT repairs, though, can be handled reason-
ably well with common tools and equipment, such as tweezers,
solder braid, and fine-tip soldering irons.
Two-terminal components (resistors, capacitors,
diodes, etc.)
Removal
1. Use two soldering irons, prefer-
ably about 25 to 40 watts, with
fine tips.
2. With a soldering iron in each
hand, hold one tip on the solder at
one end of the component and the
other tip on the other end (Figure
1.1).
3. Once the solder melts on both
ends, grip the component
between the two tips and lift it
from the circuit board.
4. Use solder braid and a soldering
iron to remove the solder from the
two pads (Figure 1.2).
Insertion
1. With a soldering iron and 60/40 or 63/37 eutectic-type solder,
melt just enough solder onto one pad to create a small mound
(Figure 1.3).
2. Grasp the component in the middle with tweezers. Melt the
small mound of solder with the iron and place the component
across the two pads (in the correct orientation, if the compo-
nent is sensitive to direction) and press it flat against the circuit
board, with one end of the component immersed in the melted
solder (Figure 1.4).
3. Hold the component in place and take the soldering iron away.
Figure 1.1.
Solder braid
Figure 1.2.
5