Qsc Powerlight 9.0PFC, Powerlight 6.0PFC, Powerlight 6.0 II User Manual

5 (1)

HEAR THE POWER OF TECHNOLOGY.

PowerLight™ Series

Two-Channel Power Amplifiers

TECHNICAL SERVICE MANUAL

▲▲

▲ PowerLight 6.0 II

▲▲ ▲▲

▲ PowerLight 6.0

▲▲ ▲▲

▲ PowerLight 9.0

▲▲

PFC

22 22

1 -CHANNEL- 2

24 24

OFF

PROTECT STANDBY

POWER

1 CHANNEL 2

POWERLIGHT 9.0

PFC

9000 WATT POWER FACTOR CORRECTED PROFESSIONAL AMPLIFIER

20 20

18 18

14 14

-00 -00

CLIP

26 26

-10dB

28 28

-20dB

30 30

SIGNAL

32 32

CLIP LIMITER

*TD-000083-00*

TD-000083-00

Rev. Prelim.

PowerLight Series

Technical Service Manual

▲▲

▲ PowerLight 6.0 II

▲▲ ▲▲

▲ PowerLight 6.0

▲▲ ▲▲

▲ PowerLight 9.0

▲▲

IMPORTANT NOTICE:

This document contains proprietary information that is the property of QSC Audio Products, Inc, and may not be disclosed, reproduced or used without express or written consent from QSC Audio Products.

QSC Audio Products, Inc. Technical Services Group

Phone: 1-800 QSC AUDIO (1-800-772-2834) USA only

+1 (714) 957-7150 Fax: +1 (714) 754-6173 Postal: 1665 MacArthur Blvd.

Costa Mesa, California 92626 USA E-mail: tech_support@qscaudio.com Web: http://www.qscaudio.com (product information and support)

http://www.qscstore.com (parts and accessory sales)

PFC

Technical Service Manual 1 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

PowerLight 9.0

PFC

PowerLight 6.0

PFC

PowerLight 9.0 II

2 QSC Audio Products, Inc.

TD-000083-00

Table of Contents

Performance Specifications ............................................................................................................................................................................................... 4

1. Introduction ..................................................................................................................................................................................................... 5

1.1 Service bulletins.............................................................................................................................................................................................................. 5

1.2 The well-equipped service bench ............................................................................................................................................................................... 5

1.3 Working with surface-mount components................................................................................................................................................................. 5

T wo-terminal components (resistors, capacitors, diodes, etc.)............................................................................................................................................................. 5

Multi-pin components (ICs, etc.) ........................................................................................................................................................................................................ 6

Three-terminal components (transistors, etc.) .................................................................................................................................................................................... 6

1.4 Series description ........................................................................................................................................................................................................... 6

1.5 Technical descriptions and theory of operation........................................................................................................................................................ 7

Power supplies ................................................................................................................................................................................................................................. 7

Audio circuitry................................................................................................................................................................................................................................... 7

2. Servicing the amplifier .................................................................................................................................................................................. 8

2.1 Mechanical disassembly and reassembly ................................................................................................................................................................. 8

Introduction...................................................................................................................................................................................................................................... 8

T ools and materials needed .............................................................................................................................................................................................................. 8

Disassembly ..................................................................................................................................................................................................................................... 8

Reassembly.................................................................................................................................................................................................................................... 11

2.2 The display board.......................................................................................................................................................................................................... 13

2.3 AC line filter ................................................................................................................................................................................................................... 13

2.4 Power supply servicing................................................................................................................................................................................................ 15

Bench testing power supply modules .............................................................................................................................................................................................. 15

Replacing switching MOSFET s in PFC models.................................................................................................................................................................................. 15

Suggestions for troubleshooting..................................................................................................................................................................................................... 17

Adjusting and calibrating the power supply module......................................................................................................................................................................... 18

2.5 AC voltage conversions................................................................................................................................................................................................ 22

2.6 Bias adjustments ........................................................................................................................................................................................................... 22

3. Troubleshooting ............................................................................................................................................................................................ 23

3.1 Initial check ................................................................................................................................................................................................................... 23

3.2 Preliminary troubleshooting........................................................................................................................................................................................ 23

3.3 Further troubleshooting ................................................................................................................................................................................................ 24

4. Parts ................................................................................................................................................................................................................. 25

4.1 Semiconductor package descriptions and pinouts ................................................................................................................................................ 25

4.2 Parts lists ........................................................................................................................................................................................................................ 33

Chassis Assembly (QSC part #WP-000268-00) ................................................................................................................................................................................ 33

Chassis Assembly (QSC part # WP-000268-02) ............................................................................................................................................................................... 34

Chassis Assembly (QSC part # WP-000260-00) ............................................................................................................................................................................... 35

Chassis Assembly (QSC part # WP-000260-02) ............................................................................................................................................................................... 36

Chassis Assembly (QSC part # WP-000170-00) ............................................................................................................................................................................... 37

Chassis Assembly (QSC part # WP-000170-02) ............................................................................................................................................................................... 38

Chassis Assembly, Rear (QSC part # WP-000271-00)....................................................................................................................................................................... 39

Chassis Assembly, Rear (QSC part # WP-000264-00)....................................................................................................................................................................... 39

Chassis Assembly, Rear (QSC Part # WP-000172-00)....................................................................................................................................................................... 40

Output PCB Assembly (QSC part # WP-000179-00) ......................................................................................................................................................................... 40

Input PCB Assembly (QSC part # WP-000272-00)............................................................................................................................................................................ 40

Input PCB Assembly (QSC part # WP-000265-00)............................................................................................................................................................................ 41

Input PCB Assembly (QSC part # WP-000175-00)............................................................................................................................................................................ 41

Input Daughterboard Assembly (QSC part # WP-000178-00)........................................................................................................................................................... 42

Audio Channel Module Assembly (QSC part number WP-000276-00)............................................................................................................................................. 42

Audio Channel Module Assembly (QSC part # WP-000182-00) ....................................................................................................................................................... 46

Power Supply Assembly (QSC part # WP-000266-00)...................................................................................................................................................................... 50

Power Supply Assembly (QSC part # WP-000266-02)...................................................................................................................................................................... 52

Power Supply Assembly (QSC part # WP-000262-00)...................................................................................................................................................................... 55

Power Supply Assembly (QSC part # WP-000262-02)...................................................................................................................................................................... 56

Power Supply Controller Assembly (QSC part # WP-000263-00)...................................................................................................................................................... 58

Power Supply Assembly (QSC part # WP-000173-00)...................................................................................................................................................................... 60

Power Supply Assembly (QSC part # WP-000180-00)...................................................................................................................................................................... 61

Power Supply Controller Assembly (QSC part # WP-000174-00)...................................................................................................................................................... 63

Display PCB Assembly (QSC part number WP-000176-00)............................................................................................................................................................... 64

Line Filter Assembly (QSC part number WP-000177-00)................................................................................................................................................................... 66

Line Filter Assembly (QSC part number WP-000181-00)................................................................................................................................................................... 66

Matched FET s................................................................................................................................................................................................................................. 67

5. Schematic diagrams .................................................................................................................................................................................... 68

Technical Service Manual 3 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

Performance Specifications

PowerLight 6.0 II PowerLight 6.0

PFC

PowerLight 9.0

PFC

OUTPUT POWER

in watts

FTC: 20 Hz–20 kHz, both channels driven

8Ω per channel 1150 (< 0.1% THD) 1400 (< 0.1% THD) 1800 (< 0.2% THD) 4Ω per channel 2050 (< 0.1% THD) 2500 (< 0.1% THD) 3200 (< 0.2% THD) 2Ω per channel 3250 (< 0.1% THD) 3250 (< 0.1% THD)

EIA: 1 kHz @ 1% THD, both channels driven

8Ω per channel 1300 1600 1950 4Ω per channel 2200 2800 3400 2Ω per channel 3500 3500 4500

Bridge Mono:

16Ω, 1 kHz, 1% THD 2600 3200 3900 8Ω, 1 kHz, 1% THD 4400 5600 6800 4Ω, 1 kHz, 1% THD 7000 7000 9000

DYNAMIC HEADROOM 0.77 dB @ 4Ω DISTORTION

THD: 20 Hz–20 kHz (8, 4, & 2Ω @ 10 dB below rated power) < 0.06% < 0.15%

(8 & 4Ω @ FTC rated power) < 0.1% (20 Hz–20 kHz) < 0.02% (20 Hz–2 kHz) < 0.03% (20 Hz–2 kHz)

20 Hz–2 kHz (2Ω) < 0.1% (20 Hz–20 kHz @ 3250 W) < 0.02% (@ 3250 W) < 0.05% (@ 4500 W)

SMPTE-IM: < 0.02% < 0.02% < 0.02%

FREQUENCY RESPONSE 20 Hz–20 kHz, ±0.15 dB

(at 10 dB below rated output power) -3 dB points: 2 Hz and 50 kHz

DAMPING FACTOR > 2000 @ 8Ω, at 1 kHz and below NOISE (unweighted 20 Hz to 20 kHz, below rated output) 107 dB 107 dB 107 dB VOLTAGE GAIN 40× (32 dB) INPUT SENSITIVITY, V RMS

full rated power @ 8Ω 2.4 v (+9.8 dBu) 2.6 v (+10.6 dBu) 3.0 v (+11.8 dBu) full rated power @ 4Ω 2.3 v (+9.5 dBu) 2.5 v (+10.2 dBu) 3.8 v (+11.2 dBu)

INPUT IMPEDANCE 10 kΩ unbalanced

20 kΩ balanced

CONTROLS Front: AC switch, Ch. 1 and Ch. 2 gain, Ch. 1 and Ch. 2 clip limiter switches

Rear: Parallel/Stereo/Bridge switch, remote power supply enable terminals

INDICATORS each channel PROTECT: Red LED CLIP: Red LED

STANDBY: Yellow LED -10 dB: Yellow LED POWER: Green LED -20 dB: Yellow LED

SIGNAL: Green LED

CONNECTORS Input: Active balanced; “Euro-style” terminal block; Neutrik “Combo” XLR

and ¼" (6.3 mm) TRS, tip and pin 2 positive Output: “Touch-Proof” binding posts (60A rated) and Neutrik Speakon™ (1 per channel) DataPort: HD 15 female connector for use with QSControl, Basis, or accessories

COOLING Four continuously variable speed fans, back-to-front air flow AMPLIFIER PROTECTION Full short circuit, open circuit, thermal, ultrasonic, and RF protection

Stable into reactive or mismatched loads

LOAD PROTECTION Turn-on/turn-off muting, OUTPUT CIRCUIT TYPE H: Full-bridge current cell vertical N-channel MOSFET linear output with Class H 4-step high efficiency circuit DIMENSIONS 19.0" (48.3 cm) wide, 3.5" (8.9 cm) tall (2 rack spaces)

17.9" (45.5 cm) rack mounting to rear support ears; 19.5” (49.5 cm) overall

WEIGHT Shipping: 59 lb. (26.8 kg) 65 lb. (29.5 kg) 65 lb. (29.5 kg)

Net: 53 lb. (24.1 kg) 59 lb. (26.8 kg) 59 lb. (26.8 kg)

POWER REQUIREMENTS Available for 120 or 220–240 VAC, 50/60 Hz POWER CONSUMPTION

(both channels driven)

Multiply currents by 0.5 for 230V units

@ 120 VAC

Typical

Full2Max

Idle

8Ω

2.5 A 10.3 A 19.3 A 39.3 A

4Ω

2.5 A 15.5 A 35.1 A 67.5 A

2Ω

2.5 A 23.8 A 47.4 A 104.7 A

Pink noise at 1/8 of full power; analogous to typical program with occasional clipping.

Pink noise at 1/3 of full power; analogous to typical program with heavy clipping.

Continuous sine wave at threshold of clipping (1% THD).

Idle

8Ω

2.5 A 10.3 A 19.3 A 39.3 A

4Ω

2.5 A 15.5 A 35.1 A 67.5 A

2Ω

2.5 A 23.8 A 47.4 A 104.7 A

Typical

Full2Max

Idle

8Ω

2.5 A 10.3A 19.3 A 39.3 A

4Ω

2.5 A 15.5A 35.1 A 67.5 A

2Ω

2.5 A 23.8A 47.4 A 104.7A

Typical

Full2Max

US patents pending

SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE

4 QSC Audio Products, Inc.

TD-000083-00

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

6.0

and PowerLight 9.0 Replacement Guidelines” (PowerLight 6.0 only); and PFC0003, “Amplifier Goes Into Protect When Turned On” (all three models).

PFC

only); PFC0002, “PFC Power Supply

PFC

and PowerLight 9.0

PFC

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.

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 smallsignal and control circuits, so they do not handle significant amounts of power; therefore, they are subject to very little stress 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 reasonably well with common tools and equipment, such as tweezers, solder braid, and fine-tip soldering irons.

T wo-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 component 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.

Technical Service Manual 5 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

Solder

Figure 1.3.

Tweezers

Figure 1.4.

Figure 1.5.

Solder

Figure 1.6.

Solder

Let the solder harden to tack the component in place.

4. Fully solder the other end of the component to its pad. Let the solder harden (Figure 1.5).

5. Fully solder the tacked end of the component to its pad (Figure

1.6).

Three-terminal components (transistors, etc.)

Removal

1. With a soldering iron and solder

braid, remove as much solder as possible from the middle terminal of the component.

2. With a soldering iron in each hand, hold one tip on the solder at the terminal at one end of the component and the other tip on the terminal at the other end.

3. When the solder on both ends

2. With fine tweezers, carefully try to lift each pin to see if it’s

free. If it’s not, touch it with the tip of the soldering iron and if necessary, use the solder braid to remove the remaining solder.

3. Repeat the process until all the pins are free and you can remove the component.

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 of solder. It is usually easiest to use a pad that corresponds to one of the end or corner pins of the component.

2. Grasp the component with tweezers. Melt the small mound of solder with the iron and place the component in the correct orientation upon its pads and gently press it flat against the circuit board, with the appropriate terminal of the component pressed into the melted solder.

3. Hold the component in place and take the soldering iron away. Let the solder harden to tack the component in place.

4. Fully solder the other terminals of the component to their pads. Let the solder harden.

5. Fully solder the tacked terminal of the component to its pad.

melts, grip the component between the two tips and lift it from the circuit board. You might need to quickly touch the pad on the middle terminal with a soldering iron to melt any remaining solder that might be holding the component down.

4. Use solder braid and a soldering iron to remove the solder from the three pads.

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 of solder.

2. Grasp the component with tweezers. Melt the small mound of solder with the iron and place the component in the correct orientation across the three pads and press it flat against the circuit board, with one terminal of the component pressed into the melted solder.

3. Hold the component in place and take the soldering iron away. Let the solder harden to tack the component in place.

4. Fully solder the other terminals of the component to their pads. Let the solder harden.

5. Fully solder the tacked terminal of the component to its pad.

Multi-pin components (ICs, etc.)

Removal

Removing a multi-pin SMT component is a delicate procedure. Ideally, you should use a soldering iron with an attachment that allows you to heat all the pins simultaneously.

If such a soldering device is not available, use this procedure:

1. Use a soldering iron and solder braid to remove as much solder as possible from the pins of the component.

1.4 Series description

QSC’s PowerLight Series amplifiers are high-performance professional audio products, designed primarily for live and touring sound and large-scale installations.

This service manual covers the three most powerful models developed for the PowerLight Series: the PowerLight 6.0 II, the PowerLight 6.0 audio channels and is three rack spaces tall. See page 2 for complete specifications.

The PowerLight 6.0 supplies with power factor correction, which reduces peak current demand by drawing power throughout the AC voltage waveform. The PowerLight 6.0 II has power supplies that don’t have PFC but are simpler and less expensive to manufacture.

The first four digits of the amplifier’s serial number indicate the month and year of manufacture in MMYY formay. For example, 0701xxxxx = July 2001). A serial number that starts with “13” indicates the amplifier was made during the model’s beta production. The PowerLight 9.0 The PowerLight 6.0 PowerLight 6.0 II, in August 2002. Many PowerLight 6.0 amplifiers, however, have been converted by QSC Technical Services into PowerLight 6.0 II amplifiers, so you may encounter PowerLight 6.0 II amplifiers with serial number date codes that precede the model’s actual release date.

The PowerLight 6.0 March 2004.

PFC

, and the PowerLight 9.0

PFC

and PowerLight 9.0

PFC

followed in March 1999, and the

PFC

and PowerLight 9.0

entered production in May 1998.

PFC

. Each one has two

PFC

feature power

PFC

ceased production in

6 QSC Audio Products, Inc.

TD-000083-00

1.5 Technical descriptions and theory of operation

Power supplies

QSC PowerLight amplifiers feature high-frequency switch-mode power supplies that help reduce noise, increase electrical efficiency, and lower weight. Two models, the PowerLight 9.0 and the PowerLight 6.0 the peak current demand from the AC mains. They accomplished this by drawing current throughout the AC voltage waveform, instead of just at the peaks, as most amplifiers and other electronic equipment do. The PowerLight 6.0 II was developed later, and its power supplies do not have power factor correction.

All three models have a fourtier class H system of multiple rail voltages to boost efficiency. A power amplifier is most efficient at or near full power, yet the dynamic nature of music and other typical audio requires much less than full power most of the time. Thus, this class H scheme creates essentially four different “full-power” levels within the amplifier

Figure 1.8. An amplifier with PFC draws current throughout the AC voltage waveform.

PFC

, had power factor correction to reduce

Figure 1.7. Amplifiers without PFC draw current only at the peaks of the AC voltage waveform.

channel. The amplifier circuitry automatically and instantaneously switches to the lowest rail voltage that will allow the reproduction of the audio signal without discontinuity.

Each amplifier channel has its own power supply. In addition, each has a small “housekeeping” supply that manages the turn-on functions before the main power supply starts up.

PFC

susceptible to RF interference, high-frequency oscillations, etc.

The audio signal passes through a pre-clipper, which prevents the audio signal from driving the output section itself into actual clipping. This maintains damping on the channel output even during clipping so that it continues to tightly control the loudspeaker motion, which is something most amplifiers cannot do. A defeatable clip limiter on each channel reduces signal level when clipping occurs; it does not prevent clipping, but reduces the amount of distortion to inaudible or barely audible levels.

An all-pass filter uses group delay to slow the audio signal by 4 µs, but the class H steps are controlled by the undelayed signal. This reduces IM distortion by ensuring that the steps are executed before the audio signal in the output section reaches the transition thresholds.

The audio signal voltage is converted into current by transistors Q87 and Q89, to be precisely bifurcated into positive and negative halves by the current steering circuitry. These current signals are the controls for the output devices.

Figure 1.10. Most amps lose feedback during clipping, resulting in loss of damping and in “clip sticking.”

Figure 1.9. The rail voltages of the output section switch among four tiers to reproduce the signal faithfully while maximizing efficiency.

The output devices are vertical MOSFETs, which are commonly used for very high power switching because of their power handling capability and general nonlinearity. Using them for linear audio amplification requires an unorthodox approach. In these three PowerLight amplifier models, each channel has eight MOSFET devices arranged in a full bridge configuration. Each one has a

Audio circuitry

The audio inputs are balanced to offer a high amount of commonmode noise rejection. The input balancing is done using an instrumentation amplifier arrangement, which uses a single op amp, arranged as a voltage follower or buffer, on each leg of the balanced input, driving a single op amp differential amplifier. The degree of common-mode rejection is dependent on the close matching of the impedance between each leg and ground and around the differential amplifier. The circuitry uses 1% precision resistors to ensure at least 40 dB of common-mode rejection.

The differential amplifier circuitry includes a first-order highfrequency roll-off, down 3 dB at 280 kHz (nearly four octaves above the high end of the audio spectrum). This makes the amplifier less

Technical Service Manual 7 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

local management circuit called a current cell that controls and linearizes the device by providing the necessary compensation to make the MOSFET’s conductivity track the signal current.

Figure 1.11. The pre-clipping scheme in the PowerLight 6.0

PFC

9.0

, and 6.0 II keeps the output signal clean despite the flat-topping of the waveform.

PFC

2. Servicing the amplifier

2.1 Mechanical disassembly and reassembly

Introduction

Replacing components will usually require removing the affected modules from the amplifier chassis. The two channels each have their own power supply module and audio module, and they share the line filter assembly and the input, output, and display board assemblies.

Within the chassis, the power supply modules are on the bottom, and the audio modules are on top. Getting at a power supply module requires removal of its audio module first.

The following instructions describe the procedure for removing both audio and both power supply modules. However, if you only need to work on one channel, you do not need to remove the modules from the other.

Tools and materials needed

• Philips screwdriver

• Diagonal cutters

• Tie wraps

• Needle-nose pliers

• Adhesive rubber foot (one per channel), QSC part # QQQQQQQQ-QQ or equivalent

• 5/64” hex (Allen) key

• 11/32” nutdriver or socket wrench

• Isopropyl alcohol and a small brush

Disassembly

Removing the top cover

1. Disconnect the amplifier from AC power and allow at least 10

minutes for internal voltages to bleed down.

2. A total of 18 screws—six with pan heads and twelve with flat

heads—hold the top cover to the chassis. Using a Philips screwdriver, remove them and set them aside. See Figure 2.1.

3. Lift the top cover up at the front until it clears the side rack ear

pieces, then lift it off the chassis. If the front of the cover is bent or dented, make sure the front edge clears the two display board headers.

Figure 2.1. Removing or installing the top cover.

Key QSC Part Description Qty. 1

WP-000170-XX Chassis assy., PL 9.0 1

CH-000079-00 Top cover 1

SC-082051-PL Screw, #8-32 × 5/16”, pan head 6

SC-080051-PU Screw, #8-32 × 5/16”, flat head 12

PL-000104-00 Insulator, high volt. 2

8 QSC Audio Products, Inc.

TD-000083-00

(2 bundles)

Figure 2.2. Seven tie wraps.

Preparing the audio modules for removal

4. There are two fishpaper insulators on each audio module.

Remove them by lifting them straight up off the heat sinks. Do not slide them forward or backward.

5. Cut the tie wraps in the seven locations shown in Figure 2.2.

6. Disconnect the display board header in front of each module.

7. Using needle-nose pliers, grasp one of the housekeeping

supply connectors and disconnect it from the modules (see Figure X.X). Repeat for the other(s).

8. Disconnect the fan connections (two on each module).

9. Spread open the latches on the power

supply control interface connections and disconnect the headers from the modules.

10. Remove the two screws that secure the audio module to the chassis partition. One screw is at the corner near the power supply connections, and the other is about 6 cm (2.5 inches) behind the housekeeping supply connections.

11. Locate the power supply connections, the five screw terminals at the front of each module. Loosen them and remove the wires.

Figure 2.3. The connections to

Power supply control (8-pin

header)

Power supply

(wires 0 through 4)

the audio module.

Fan (4-pin header; 2 pins per fan)

12. There may be an adhesive rubber foot wedged in front of each module circuit board. Grasp it with the needle-nose pliers and pull it out.

Removing the chassis rear panel

13. Remove the four screws on the rear panel

(see Figure 2.4).

14. Tip the amplifier up on its right side (the side opposite the power cord). There are three flat head screws in a line along the center of the side panel. Remove them.

15. Remove the two pan head screws on the rear rack tab.

16. Set the amp back down and remove the two pan head screws from the other rear rack tab.

17. Remove the two screws under the power cord.

18. Tip the chassis rear panel back and disconnect the header from the input board.

19. Lift the fan wires clear of the heat sinks on the audio modules.

From input board

(detachable latching header)

Housekeeping supply

Display board

(via multiconductor ribbon cable)

Technical Service Manual 9 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

Figure 2.4. Removing or installing the chassis rear panel.

Locations of ground screws for audio modules

Key QSC Part Description Qty. 1

CH-000078-00 Chassis, PL 9.0 1

WP-000172-00 Rear chassis assembly 1

SC-082051-PL Screw, #8 × 5/16”, pan head 4

SC-080051-PU Screw, #8-32 × 5/16”, flat head 4

SC-082051-PL Screw, #8 × 5/16”, pan head 2

20. Remove the chassis rear panel from the main chassis.

21. Cut and remove the tie wraps that secure the output wires to

the rear panel.

Removing the audio modules

22. There is a ground screw at the back of each audio module

(see Figure 2.4). Remove it.

23. Slide the audio module toward the front of the chassis so that its keyed mounting holes are clear of the standoffs.

24. Lift up the back of the audio module slightly, then lift the entire module clear of the chassis.

Removing the power supply modules

25. If you need to remove one or both power supply modules, you

will need to remove both audio modules. Invert one audio module and set it on top of the other channel’s audio module, then set them aside.

26. Straighten the five power supply wires on each channel.

27. Remove the three screws from the front of the chassis

partition.

28. Remove the side-facing screw from the front of the partition on channel 1’s side.

29. Remove two black pan head screws from the center line of the chassis partition.

30. Slide the chassis partition back, then lift up on the channel 2 side of it. Press down on the back of the partition, then lift it clear of the chassis.

31. Remove the two screws at the front of the power supply module.

32. Use a 5/64” hex (Allen) key to remove the screw at the rear of the power supply module.

33. Use an 11/32” nutdriver or socket wrench to remove the two nuts on the AC connection (a white and a black wire).

34. Slide the power supply module toward the rear of the chassis, then lift it up and out of the amplifier.

Inspecting the power supply modules

35. Visually inspect the power supply module. Check the leads of

diodes D1 and D12, because they sometimes crack due to flexing of the circuit board.

36. Using isopropyl alcohol and a brush, clean any dirty or charred parts of the circuit board. Look for burned-off circuit board traces, especially around the switching MOSFETs; missing or damaged ones can be repaired using a trace repair kit. If the

10 QSC Audio Products, Inc.

TD-000083-00

Key QSC Part Description Qty. 1

CH-000078-00 Chassis, PL 9.0 1

PL-000107-00 Heatsink insulator 2

CH-000080-00 Chassis horiz. partition 1

SC-080051-PS Screw, #8-32 × 5/16”, SEMS 3

SC-082051-PU Screw, #8-32 × 5/16”, pan head 3

SC-060042-PP Screw, #6-32 × 1/4”, SEMS 3 PL-000109-00 Insulator, mega platform 2

7 8

PL-000137-00 2

Insulator, amp rear bottom

Figure 2.5. Removing or installing the chassis partition.

circuit board is burned into the fiber layers or badly damaged, replace the entire module.

See instructions for servicing the power supply module elsewhere in this chapter.

4. Insert and tighten the two screws at the front of the module.

5. Install the chassis partition.

6. Insert and tighten the two screws along the center line of the chassis partition.

7. Insert and tighten the side-facing screw at the front of the

Reassembly

Reassembling the amplifier chassis is essentially reversing the order of the disassembly process.

Installing the power supply module

1. Align the keyed slots in the power supply module circuit board with the chassis standoffs. Watch out for the fish paper insulators, which may get caught underneath. Drop the module into place on the standoffs and slide it forward.

2. Using the 11/32” nutdriver or socket wrench, attach the AC wires to the module. The black wire attaches in front (closer to the front of the amplifier chassis) of the white one.

3. Using the 5/64” hex (Allen) key, insert and tighten the screw at the rear of the power supply module.

Technical Service Manual 11 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

chassis partition on the channel 1 side.

8. Insert and tighten the three screws at the front of the chassis partition.

Installing the audio modules

9. Place the audio modules in position.

10. Insert and tighten the ground screw at the back of each module (see Figure 2.4).

11. With new tie wraps, secure the output wires to the chassis rear panel.

12. Loosely insert one screw on each end of the chassis rear panel, then tighten them both.

13. Insert and tighten the other two screws.

Figure 2.6. Removing or installing the power supply modules.

Key QSC Part Description Qty. 1

CH-000078-00 Chassis, PL 9.0 1

WP-000173-00 Power supply PCB assy. (120V) 2 WP-000180-00

SC-040155-00 Screw, #4-40 shoulder hex head 2

SC-060042-PP Screw, #6-32 × 1/4”, SEMS 4

NW-080500-KP Keps nut, #8-32 4

Power supply PCB assy. (230V) 2

14. Insert and tighten the two screws under the power cord.

15. On each audio module, tuck the two fan wires into one or two slots of the heat sink. Reconnect both to the four-pin header on the audio module.

16. Reconnect the input headers to the audio module.

17. Tip the amplifier up on its right side (the side opposite the power cord). Insert and tighten the three flat head screws in a line along the center of the side panel.

18. Set the amp back down. Reconnect the five power supply

20. Reconnect the housekeeping supply wires at the front of the module.

21. Using five new tie wraps, secure the wire bundles to the chassis partition at or near the front of the amplifier. Each secures one bundle, except for the one at the center, which secures two.

22. Using two new tie wraps, re-connect and secure the two headers to the display board.

23. Re-install the top cover of the amplifier.

wires, 0 through 4, to their respective screw terminals at the front of the module. Make sure they are placed in the proper sequence—from left to right, as viewed from the front of the amplifier:.0, 1, 2, 3, and 4.

19. Reconnect the power supply control interface. Make sure the latching wings of the board-mounted connector are up all the way.

12 QSC Audio Products, Inc.

TD-000083-00

Key QSC Part Description Qty. 1

CH-000078-00 Chassis, PL 9.0 1

HW-000079-00 Hex standoff #6-32 x 9/16” 5

WP-000176-00 Display PCB assy. 1

SC-060042-PP Screw, #6-32 × 1/4”, SEMS 2

HW-060080-HW Hex standoff #6-32 x 1/2” 3

PL-000054-00 Knob fab. 2

Figure 5.7. Removing or installing the display board.

2.2 The display board

The display board contains the signal metering, clip, power, and status LEDs. It also holds the two gain potentiometers. LED failures are very rare, but you will need to remove the board if the gain pots become damaged or badly contaminated. See Figure 2.7.

2.3 AC line filter

The AC line filter is an important part of the amplifier because it reduces noise and interference from the internal switching circuitry to prevent its radiation into the AC wiring. It also contains part of the housekeeping supplies for the two audio modules; without the housekeeping supplies, the amplifier’s power supply modules will not start up even if they are in working order.

The line filters are the same among the three amplifier models, but the 120-volt and 230-volt versions are not interchangeable. See Figure 2.8.

Technical Service Manual 13 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

120V version

230V version

Key QSC Part Description Qty. 1

WP-000177-00 Line filter PCB assy. 1

NW-000021-03 Flat Washer 1

WP-000042-00 AC power cord assy., 30A 125V 1

SW-000027-SW Switch AC 1

Key QSC Part Description Qty. 1

WP-000181-00 Line filter PCB assy. (230V) 1

C0-000099-00 Connector line side flange 1

SC-083061-PU Screw, #8-18 × 3/8”, flat head 2

SW-000027-SW Switch AC 1

WC-000022-00 Cord set 3 cond. 16A 250 VAC 1

Figure 2.8. Assembly details of the AC line filter.

14 QSC Audio Products, Inc.

TD-000083-00

2.4 Power supply servicing

Bench testing power supply modules

The housekeeping supplies provide electrical power to certain control circuitry in their respective audio channel modules. The control circuitry in turn enables the power supply module to operate. Thus, a power supply module normally will not operate when it is not connected to an audio channel.

The remote control circuit shown in Figure 2.9 allows the power supply module to operate without an audio channel module connected. This is useful for verifying the power supply’s operation independently of other amplifier circuitry.

POWER SUPPLY TEST REMOTE CONTROLLER

THIS REMOTE CONTROL IS USED TO TURN ON THE PFC POWER SUPPLY VIA J100 ON THE CONTROLLER BOARD.

CLOSING POWER SWITCH S1 ENABLES THE POWER SUPPLY, AND LED LD1:2 WILL GLOW GREEN. THE AC INPUT VOLTAGE APPLIED TO THE PS

POWER SUPPLY

CONTROLLER BOARD

MODULE REACHES THE TURN-ON THRESHOLD (65 VAC FOR 120V UNIT OR 130 VAC FOR 230V UNIT), LED1:1 WILL ALSO LIGHT, AND THE RESULTING COLOR WILL BE YELLOW-ORANGE.

Figure 2.9. Remote controller for power supply testing.

Parts list

• 8-pin header (J1)

• 9-volt battery (B1)

• SPST switch (S1)

• Three-lead tri-color LED (LD1)

• 18 kΩ resistor (R1)

• Two 1.5 kΩ resistors (R2 and R3)

Replacement parts

WHEN

Replacing switching MOSFETs in PFC models

Replacing the power MOSFETs and their associated components requires that the power supply modules be removed from the amplifier.

T ools and materials required:

• Soldering iron

• Rosin-core solder (60/40 or 63/37 eutectic type)

• Long-nose pliers

• #1 and #2 Philips screwdrivers

• Thermal grease (heat sink compound)

• Small diagonal cutters

• Desoldering equipment or solder braid

• Micro-torque wrench with 9/64” Allen (hex) and #1 Philips bits If fuse F1 on the power supply module’s printed circuit board (PCB)

is blown, you will also need a 1A 250V 5×20 mm slow-blow fuse (QSC part # MS-000113-00) to replace it with. Also, the alumina insulator between the diodes and the heat sink is very fragile and often breaks when the diodes are removed; replace it with QSC part # PL-000085-00.

To ensure that the devices will share power equally, the four MOSFETs must have similar V

. For a set of four matched

DSS

MOSFETs, as pre-sorted by QSC production, order QSC part #

WP-000056-00.

Procedure: replacing Q1, Q2, Q3, and Q4

1. Remove the heat sink assembly to which the MOSFETs are

attached. To do this, remove the clamps on the four diodes (D1, D2, D7,

and D8) to free them from the heat sink. Keep the two mica insulators (from between the diodes and clamps) and set them aside for when you reassemble the heat sink and diodes later; they are fragile, so be careful handling them but replace any that are damaged. The QSC part number is PL-000059-00. Remove the alumina insulator

Figure 2.10. Bottom view of a MOSFET

ecnerefertraP #trapweN noitpircseD #trapdlosecalper… noitpircseD ?sledomhcihW

4Q&,3Q,2Q,1Q

8R&,7R,6R,5R

8D&,7D,2D,1D 8D&,7D,2D,1D

02C

00-881000-DQ TEFSOMA5505N55FXI

01-10574.-ER 57.4 ΩΩΩΩΩ rotsiserttaw-¼

00-381000-DQ edoid80SPE06

00-281000-DQ edoid21SPE06

00-900014-AC roticapacV052Fµ1.0

00-911000-DQTEFSOMA8405N84FXI

01-20001.-ER1Ω rotsiserttaw-¼

00-621000-DQedoidA60-06IESD 00-761000-DQedoid21-06IESD 00-004743-ACroticapacV004Fµ740.0

sledomllA

ylnosledomV021

ylnosledomV032

sledomllA

Technical Service Manual 15 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

“Diode” end of heat sink

Figure 2.10: The heat sink assembly, with all four MOSFETs attached. The “diode” end of the heat sink is at right; the slots in the MOSFETs would face to the left.

(from between the diodes and the heat sink); it is extremely fragile, so it is best to replace it during reassembly with a new one.

Then remove the 16 screws that attach the MOSFETs to the printed circuit board (PCB); if the MOSFETs are blown, some of the mounting screws may be melted or damaged. The new MOSFETs come with new mounting screws with captive washers, so there is no need to save old ones for reuse.

Remove the other four mounting screws so that the heat sink assembly is free from the circuit board. Set the hardware aside.

Find where the twisted wire lead from the heat sink’s thermal sensor attaches to a pair of pins on the board, and unplug it. Detach the gate drive cable, which is an 8-conductor ribbon cable that plugs into an 8-pin header. Lift the heat sink and MOSFET assembly from the board. If the strip of fishpaper (Figure 2.11) remains stuck to the PCB, leave it there; if it comes loose, set it aside for re-assembly later.

Figure 2.11. The silk screen on the circuit board shows the correct orientation of the MOSFETs. This photo also shows the four resistors (R5–R8) to be replaced.

2. Remove the MOSFETs from the heat sink. Thoroughly clean the old thermal grease off the heat sink. Apply fresh thermal grease to the new MOSFETs (QSC part # QD-000188-00) and attach them to the heat sink.

Make sure the new MOSFETs are correctly oriented. One end of each MOSFET has a mounting hole, while the other has an open-ended slot (see Figure 2.9). Each MOSFET must be

away

mounted so the slot end faces

from the diode end of the heat sink (see Figure 5.11). Try to get the MOSFETs evenly spaced and as close to perfectly in line as you can. The silk screen print on the circuit board (see Figure 5.12) shows the correct orientation.

Tighten the MOSFET mounting screws to 32–35 lb-in (3.6–4.0 N-m) torque. Do not over-torque them.

3. Remove the four diodes on the circuit board (D1, D2, D7, and D8). See Figure 2.12.

4. Check the value and rating labeled on capacitor C20 (see Figure 2.13). If it is not a 0.1 µF 250V capacitor (early modules will have the original 0.047 µF 400V component instead), replace it with QSC part # CA-410009-00.

5. Remove resistors R5 through R8 (see Figure 2.11) and replace them with 4.75Ω ¼-watt resistors (QSC part # RE-.47501-10).

6. Set the MOSFET and heat sink assembly upside-down and place the PCB on top of it. Make sure all the threaded holes in the heat sink and the MOSFETs line up exactly with the holes in the board. If any MOSFETs don’t line up, reposition them so they do because misaligned mounting screws can damage them when tightened.

Make sure the fishpaper strip is in place, and then reattach the MOSFET and heat sink assembly to the PCB. Make sure you use the correct screws and washers in each location. Tighten the four heat sink screws to 32–35 lb-in (3.6–4.0 N-m) torque and the MOSFET mounting screws to 12 lb-in (1.4 Nm). Do not over-torque them.

CAUTION: Overtightening its mounting screws will destroy a MOSFET. When tightening a screw, use the split lockwasher as a visual guide; as soon as it is flattened, the screw is tight enough.

Plug the thermal sensor lead onto its two pins on the circuit board.

7. Clear any solder from the circuit board holes for the four diodes. Apply a thin coating of new thermal grease to both sides of

the alumina strip and set it in place on the heat sink. Insert the four new diodes (120V models: QSC part #

QD-000183-00; 230V models: QSC part # QD-000182-00) into their holes in the PCB, but do not solder them in place yet. Then set the two mica insulators in place over the diodes (they will overlap in the middle), and clamp and fasten the diodes to the heat sink; tighten the screws to 32–35 lb-in (3.6–4.0 N-m) torque. Do not over-torque them. As you do

16 QSC Audio Products, Inc.

TD-000083-00

Figure 2.12. These four diodes need to be replaced.

this, make sure the diodes are straight and evenly spaced, and reposition them if necessary.

8. Solder the four diodes to the circuit board.

9. Reattach the gate drive cable.

10. Check the fuse (see Figure 2.14). If it is blown, replace it with

a slow-blow 1A 250V 5×20 mm fuse (QSC part #

MS-000113-00).

11. Repeat the procedure for the other channel’s power supply

board if it also has failed or is to be updated.

Capacitor C20

Figure 2.13. Capacitor C20 may also need replacement. See the text.

Fuse F1

Figure 2.14. Fuse F1 may need replacing.

Suggestions for troubleshooting

If you are repairing a failed power supply module and not simply upgrading a working one, you should determine whether other components have also failed.

Typical collateral failures around PFC power supply module failures include:

Blown high rail diodes: Check D12 and D14 for sooty or

blackened thermal grease around their edges or for any other signs of damage. If you suspect that they might be damaged, remove them from the circuit board and check them with the diode test function on a DMM. Replace them if necessary (QSC part # QD-000126-00). These diodes are clamped onto the other heat sink, at the end next to the power transformer. If you remove the diodes, thoroughly clean away the old thermal grease from that portion of the heat sink and from the mica insulators; apply fresh thermal grease when you reassemble or replace them.

Blown driver ICs: The two MIC4452BN MOSFET driver ICs, U1

and U3, are under the MOSFET heat sink. Frequently, when MOSFETs fail, the driver IC associated with the transistor(s) fails, too. The IC’s QSC part # is IC-000064-00.

Fuses: Conditions that cause the MOSFETs to fail also frequently

cause the fuses on the AC line filter to blow. The filter circuit board runs along the side of the amplifier between the AC power cable and the AC power switch. Each channel has two fast-blow ceramic AC fuses, for a total of four (120V models: 125V 25A, QSC part # MS-000112-00; 230V models: 250V 15A, QSC part # MS-150250-FU). Check them and replace any that are blown. Also on the AC line filter board are the housekeeping supplies for each channel; if they do not work, the channels will not start even if the power supply modules are in perfect working order. The housekeeping supplies each use a 250V 1A slowblow fuse (QSC part # MS-000113-00).

Technical Service Manual 17 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

Adjusting and calibrating the power supply module

Adjusting and calibrating the power supply card will help ensure the success of the repair; this portion of the service bulletin describes a series of five procedures for doing so. Because of the specialized nature of the power supply fixture required for these procedures, it can only be performed at the QSC factory by trained personnel. Follow these procedures exactly and in order.

There are four trimpots, VR1–VR4 (see Figure 2.14), on the controller card that must be adjusted correctly before reinstalling the power supply in the amplifier:

VR1 On the PL 9.0

sets V

OUT

/26.6.

PFC

, this trimpot sets V

/32; on the PL 6.0

OUT

PFC

, it

VR2 This trimpot is for balancing the transformer to the PFC circuitry. VR3 This trimpot sets the maximum 2-ohm output power. For the

PFC

PL 9.0

, it will be set for 4500 watts @ 2 ohms at 2 kHz; for

the PL 6.0

PFC

, it will be set for 3600 watts @ 2 ohms at 2 kHz.

VR4 This trimpot sets the power supply’s idle voltage. For the PL

PFC

9.0

, it will be set for 191.3 volts DC; for the PL 6.0

PFC

it will

be 166.5 volts DC.

VR4

VR3

VR1

VR2

Figure 2.15. The locations of the four trimpots, VR1–VR4

Tools and materials needed:

• PFC power supply fixture with external power supply and CMP (Control-Monitor-Power) box

• Two digital multimeters (DMM #1 and #2) with clip-on leads

• Digital multimeter (DMM #3) with clamp-on AC current probe

• 0–240 VAC Variac™, Powerstat™, or similar variable AC transformer; 60 amperes or higher rating, with RMS voltage and current metering

• 120 VAC power (for the fixture’s housekeeping supply)

• Four-channel oscilloscope with ×1/×10 probes

• Oscilloscope with differential probe

step 10 of the V

procedure)

OUT

• Small pocket-type flat-blade screwdriver

• Grounded anti-static work surface

• Audio Precision (AP) workstation with PFC test procedure files* and 2-ohm load resistor banks (mimimum power handling capacity: 1250 watts per 8-ohm resistor; 5000 watts total in 2-ohm configuration).

*The four AP test procedure files are available on the QSC Technical

Support CD-ROM: Pfcxf.tst; Pfcpwr2k.tst; Pfcpwr20.tst; and Pfctherm.tst.

(optional; see

Figure 2.16. The front of the fixture. The amplifier channel’s gain control is to the right, out of the picture

The PFC power supply fixture

The PFC power supply fixture is a special test bed for PowerLight 6.0 and 9.0 supply modules. It has the necessary connections and indicators for adjusting, calibrating, and testing the modules. It also contains one audio channel of a PowerLight 9.0 to allow testing of the module’s capability to power an actual amplifier channel. The fixture is custom built by QSC.

Front panel switches and indicators

From left to right (Figure 2.14):

• Power switch. For the AC lines to the power supply module being tested.

• Power indicator. It lights when the fixture is connected to AC power and is turned on.

• Blown fuse indicator. Connected across the large fuse under the door in the top of the fixture chassis, this indicator will light if the fuse blows. The fuse, however, is merely a backup in case the CMP box’s solid-state electronic fuse malfunctions.

• Protect, Standby, and Power indicators. In the portions of the test that use the amplifier channel, these LEDs function just as they do on a regular amplifier.

• Fan switch. Some portions of these procedures require the module fans running, and others need them off.

• “Set V

• “I for checking the module’s I

• “I module’s I

Rear panel switches and attachments

From left to right (Figure 2.15):

• Audio input. This is where to connect the signal output from the AP workstation.

• DC high rail outputs. These are two pairs of red and black binding posts, and they carry the DC output of the supply module’s high rails. Connect DMM #1 to one of these sets of binding posts.

• Audio output. This Neutrik Speakon connector carries the audio output of the fixture’s amplifier channel. Connect this

” switch. This switch is used for the first procedure.

OUT

” switch. This switch also is used in the first procedure

SET

” indicator. This tri-color LED indicates the status of the

SET

circuit.

SET

circuit.

SET

18 QSC Audio Products, Inc.

TD-000083-00

Audio signal input

from Audio Precision

workstation

DC high rail outputs: for

PFC PFC

PL 9.0 ; for PL 6.0

Red = +; Black = -

The two sets of binding posts are

in parallel. Connect DMM #1 to

191.3 V

166.5 V

one set.

Audio signal output

to Audio Precision

workstation and load

resistors

Figure 2.17. The fixture’s rear panel.

Transformer flux sample for balancing procedure. Connect to oscilloscope

using ×1 probe.

(Do not connect to Variac!)

Connect to external DC supply. Watch polarity:

Red = +; Black = -

120 VAC for fixture's housekeeping supply

Power switch for

housekeeping

supply.

• Upper barrier strip. Connect the DC rail wires to the upper barrier strip for the other procedures.

• Control connection. Above the barrier strips is a multiconductor cable that connects to the 8-pin header on the controller card of the power supply module under test.

• AC wires. Located at the top of the front panel, these two wires connect to points E2 and E3 on the supply module.

output to the AP workstation and to the load resistors.

• Transformer flux sample. Connect the tip of an oscilloscope’s ×1 probe to the exposed conductor at the tip of this attachment, and connect the probe’s reference clip to the loop. This is used in the transformer balancing, the third procedure in the supply module adjustment and calibration.

• DC supply input. This dual binding post set is for connecting the fixture to the external power supply.

• 120 VAC power cord. This connects to a regular AC outlet and provides power for the fixture’s “housekeeping” supply, which powers the various circuits and indicators.

• Housekeeping supply power switch. This small rocker switch lets you turn off the housekeeping supply when the fixture is not in use.

• Fixture power cord. This large power cord connects to the Variac and provides AC power for the power supply module under test.

Other attachments

See Figure 2.17.

• Lower barrier strip. Connect the supply module’s five black DC rail wires to the lower barrier strip’s terminals for the first procedure, setting V

OUT

Procedure 1 of 5: Setting V

OUT

1 Turn off all power to the fixture and turn the Variac all the

way down. Set the power supply module in place atop the fixture, as shown in Figure 2.18.

2 On the test fixture, set switches V

/32 and I

OUT

SET

in the

position. Turn off the fan switch.

3. On the power supply module, disconnect the gate drive cable (Figure 13).

4. Connect the two AC line wires to the stud terminals on the PCB: white to E2 on the left, black to E3 on the right. Use the long insulated threaded posts to secure the wires to the terminals.

5. Connect the power supply module’s five black DC output wires, labeled 0 through 4, to the screw terminals on the

lower

barrier strip (Figure 10). Keep them in order; do not

cross any of them.

6. The external power supply has two dual banana sockets—one is labeled dual banana plug to the external power supply’s

active

and the other,

dummy

. Connect the fixture’s

active

socket.

7. Plug the AC lines for both the external DC supply and the fixture into the Variac.

8. Set the CMP boxe’s electronic fuse to a trip threshold of 5 amperes.

Switches and

LED indicators

Figure 2.18. The two barrier strips. Use the lower one for the first adjustment (setting V

/32 or V

OUT

Ext. DC

AC connection

supply

Solid-

state fuse

26.6), and the upper one for the other adjustments. Figure 2.19. The power supply module loaded onto the test fixture.

Technical Service Manual 19 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

The CMP box

The CMP box has two digital panel meters that monitor AC voltage and current and a solid-state electronic AC fuse that can be set to trip specific current levels from 0 to 100 amperes.

To set the current trip level, flip the trip set switch down; the AC ammeter will then read the trip current setting. Use the trip set knob to adjust the desired trip point, then flip the switch up.

The BNC jack provides an AC voltage proportional to the AC current: 100 mV RMS = 1.0 ampere RMS. This is useful in the transformer balancing procedure because it allows the use of an external voltmeter with finer resolution (>3 decimal places) than the panel ammeter has.

Trip set switch up:

reads AC current;

Trip set switch down:

reads trip current setting

AC voltage

Adjusts trip current

of solid state fuse

Trip set switch:

for normal solid state fuse function;

to set solid state fuse trip

DOWN

0–280 VAC in

from Variac

Figure 2.20. The CMP box. The variable AC outlet for the test fixture is on the back of the box.

Indicates that the

solid state fuse

circuit has tripped

AC current sample for

external DMM

100 mV = 1.0 A

Press switch down and back up to reset the

solid state fuse.

Gate drive cable

Figure 2.21. The gate drive cable for the MOSFETs. Disconnect it here for the V

9. Connect DMM #1 to one set of the parallel DC V

procedure.

OUT

terminals

OUT

on the back of the fixture. Connect DMM #2 to the controller card, with the ground or reference lead on the tab of U8, a +12V regulator, and the hot lead on the left leg of capacitor C34. On the board, this point is labeled “VOUT/32.”

10.

Note: this step is optional because the replacement diodes specified in this bulletin do not have the leakage problems that many of the original fast diodes had.

Through a differential probe, connect an oscilloscope input between resistor R31 (labeled “OSC”) and ground; this will allow you to view the output of the diodes to see if any are leaky.

11. Turn the fixture power switch on. Turn up the Variac gradually until DMM #1 reads 190 volts DC (for the PL 9.0) or 166 volts (for the PL 6.0). You don’t need to measure the AC voltage from the Variac yet.

12. Adjust VR1 to obtain a reading on DMM #2 of 5.94 volts DC (for the PL 9.0) or 6.20 volts DC (for the PL 6.0).

13. Flip the I switch lights green or orange, I

switch down. If the LED indicator next to the

SET

is good; if red, it is bad and

SET

should be rejected for controller board replacement or repair.

14. Turn down the Variac all the way. Turn off the fixture’s AC switch. Unplug the external supply’s AC line from the Variac.

15. Set the I

SET

and V

/32 switches

OUT

down

. Remove DMM #2’s

leads from the controller card.

16. Wait a few seconds for the capacitors to discharge and DMM #1’s voltage reading to drop to 60 volts or less.

Important note about repaired PFC power supply modules

After repairing a failed power supply module that had already been calibrated before its failure, either in production or in Technical Services, the VOUT/32 and VOUT @ idle voltages in Procedure 1 only need to be checked and not fully adjusted, unless the measured high rail voltage is not 191.3 volts, ±1.5 volts, for the PL 9.0 or 166.5 volts, ±1.5 volts, for the PL 6.0. If the high rail voltages are outside this range, then the module will require full adjustment and calibration.

Procedure 2 of 5: Adjusting idle voltage

1. Re-attach the gate drive cable on the power supply module. Also, disconnect the five DC rail output wires on the right end of the module from the lower barrier strip and attach them to the corresponding screw terminals on the upper barrier strip. Make sure the screw connections are tight and secure.

2. Turn the fixture’s AC switch on and turn the Variac up to the appropriate AC voltage: 120 volts AC for a 120V module, or 230 volts AC for a 230V module. The power supply will turn on and begin to draw current when the AC voltage reaches about the halfway point.

3. Adjust VR4 to obtain the a reading of 191.3 volts DC (for the PL 9.0) or 166.5 volts DC (for the PL 9.0) on DMM #1.

20 QSC Audio Products, Inc.

TD-000083-00

Procedure 3 of 5: Adjusting transformer balance

This is done in three stages. In the first two, watch the transformer flux “bubble” waveform on the oscilloscope, and on the third, adjust the AC current to a minimum. To prevent overcurrent cutback due to undervoltage, adjust the Variac to 130 volts for 120-volt modules or 260 volts for 230-volt modules.

1. Set the CMP box’s electronic fuse to a trip threshold of 20 amperes (for a 120V module) or 10 amperes (for a 230V module) and turn on the fans.

2. Start the PFC test file (Pfcxf.tst) on the AP workstation. It will put out a 2 kHz sine wave at 0.1 volt RMS and will switch the load resistance to 2 ohms. Turn the fixture’s gain control all the way up.

3. Step the signal level up in 0.1 volt increments and watch the transformer flux “bubble” signal on the oscilloscope (vertical scale: 20 or 50 V/div; horizontal scale: 1 or 2 ms/div; ×1 scale). At each step, adjust VR2 to get a smooth, balanced signal. See Figure 14. There should be no spurious oscillations or noise visible.

4. When the audio signal reaches a particular level, the CMP box’s electronic fuse will trip. Set the audio signal back to 0.1 volt.

5. Reset the trip point to 40 amperes (for a 120V module) or 20 amperes (for a 230V module) and repeat steps 2 and 3. The electronic fuse should trip at about 2.8 kW of output (measured on the AP)

with approximately 1.4 volts input.

6. Reduce the AP’s signal level to 0.1 volt. Reset the electronic fuse and increase the signal level so that the output is about

2.5 kW. Gently adjust VR2 to null the AC current on DMM #3 to a minimum.

7. Turn the Variac down to zero and set the electronic fuse to 60 amperes.

Procedure 4 of 5: Adjusting 2-ohm limits

1. If this is a brand new module (not a repair), set VR3 to approximately 4 o’clock. If it is a repair or has otherwise already been calibrated at some time, leave VR3 alone until after the first power sweep.

2. Set the Variac to 130 volts (for 120V modules) or 260 volts (for 230V modules).

3. Run the AP test file (Pfcpwr2k.tst) for a 2-ohm power sweep test at 2 kHz.

4. Watch the power sweep on the AP monitor and see where the power cutback occurs. The target output power level at 2 kHz is about 4.6 to 4.7 kW for the PL 9.0 or 3.6 to 3.7 kW for the PL 6.0. If the cutback point is not in the target range, carefully adjust VR3 and then repeat the power sweep. It may take more than two or three tries to get the right setting.

CAUTION: During the power sweep, keep a finger on the reset switch of the CMP box. If anything abnormal happens, such as power cutback at a low level, or audible noise from the supply module’s transformers, switch

down

and hit F1 on the AP computer keyboard to abort

immediately

flip the reset

the sweep test. If you stopped the test due to transformer noise, go back and

start over at the transformer balancing procedure. If you had not aborted the power sweep, in a short time you would have destroyed the MOSFETs.

If you stopped the test for any other abnormality, you must troubleshoot and repair the supply module before continuing.

5. Load the AP test file Pfcpwr20.tst, which will change the signal frequency to 20 kHz, and repeat step 4. This time, verify that the power cutback does not occur until approximately 4.5 kW for the PL 9.0 or 3.6 kW for the PL 6.0.

6. After competing the power sweeps, press F1 on the AP computer keyboard.

Procedure 5 of 5: Thermal test

1. On the AP workstation, load the thermal test file Pfctherm.tst. It should select the Pseudo (pink noise) waveform at 2.7 volts RMS amplitude. Make sure the fixture’s gain control is turned up full. Load the fixture output with the 2-ohm resistance and shut off the fans.

2. The power supply module should shut down within one minute. The light.

3. After the module shuts down, turn on the fans and await its recovery.

PROTECT

indicator LED on the front panel will

Figure 2.22. A well-balanced transformer flux “bubble.”

Technical Service Manual 21 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

4. Turn off the fixture’s AC switch. Turn down the Variac to zero. Turning off the fixture’s AC switch will automatically bleed the capacitors down. Disconnect the module from the test fixture and set the AP workstation back to sine wave and 0 volt RMS.

2.5 AC voltage conversions

WARNING: Regulatory agencies require that any operating

voltage conversions from 120 volts to any other voltage be done

only

by QSC’s factory service. Any other operating voltage

conversions may be done only by a QSC-authorized service center or international distributor.

The power supply modules and line filter modules in the PowerLight 6.0 II, PowerLight 6.0 made for specific AC line voltages; they cannot be converted from one to another. To convert an amplifier from120 to 230 volts AC or vice-versa requires replacing both power supply modules and the AC line filter. For this reason, it is seldom economically justifiable to convert one of these models.

PFC

, and PowerLight 9.0

PFC

are

2.6 Bias adjustments

These three amplifier models have a trimpot for bias adjustment on each audio channel. However, adjusting it is far more complex than on most amplifiers, so it should only be done when working on the module at board level, or as an emergency measure if the module is running too hot at idle.

22 QSC Audio Products, Inc.

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3. Troubleshooting

Because of the high complexity of the circuitry used in the amplifiers covered by this manual, most, if not all, of your troubleshooting efforts will be at board level. Proper componentlevel troubleshooting and service will also usually require specialized test fixtures that may not be economically sensible to have unless you do a high volume of service work on these amplifiers. See the Servicing chapter of this manual for information on these fixtures.

3.1 Initial check

When first checking the operation of a suspect amplifier on the bench, always turn your variable transformer down to zero before plugging the amplifier in. After you turn the amplifier on, gradually turn up the AC voltage as you observe the amplifier’s behavior and its current draw; this will help you determine what, if anything, is wrong with it. If you see or smell smoke, flames, or any other signs of short circuits or excessive current draw, quickly turn the AC back down to zero. If no such problems occur , it is usually safe to turn the AC up to the amplifier’s full operating voltage for further testing. The following procedure will help you determine if the amplifier has a problem and if so, where it may be located.

Starting at zero volts

1. Start with the variable transformer at zero.

2. Connect an AC voltmeter to monitor the transformer output

and an AC ammeter to monitor the current delivered to the amplifier.

3. Connect the amplifier to the output of the variable transformer.

4. Turn on the amplifier.

LED activity starts

5. Gradually turn up the AC voltage. When it reaches about 25%

of the amplifier’s operating voltage (30 volts for a 120-volt model or 60 volts for a 230-volt model), the power LEDs on both channels should start to flicker. By the time it reaches about 40% (50 volts for a 120-volt model or 100 volts for a 230-volt model), both power LEDs and both protect LEDs should be on.

6. Continue increasing the AC voltage. When it reaches about 70 volts (120-volt model) or 140 volts (230-volt model), both protect LEDs should go out and all four fans should start up.

Check current draw

7. At this point, the current draw for a PowerLight 6.0

PowerLight 6.0 II should be about 2 A or less for a 120-volt model or 1 A or less for a 230-volt one. For a PowerLight

PFC

9.0

, it should be about 2.5 A or less (120-volt model) or 1.25

A or less (230-volt model).

PFC

8. If all is well, you can safely increase the AC voltage to the amplifier’s normal operating level and test its audio performance. Once the AC voltage is at full, the amplifier should behave normally. On the left side of the front panel, the two power LEDs should be lit, while the standby and protect LEDs should not. On the right, the signal, -20 dB, -10 dB, and clip LEDs should light only in response to an output signal. If they do not, continue by following the preliminary troubleshooting guide.

3.2 Preliminary troubleshooting

Abnormal behavior of the amplifier indicates some problem in one or more of its parts. You can use the observed patterns of this behavior to help deduce where the problem lies. The amplifier has two channels with independent power supplies; a defect may exist on one channel that does not affect the other.

Power, Standby, and Protect LEDs: None lit on one or both channels

• The main fuse for the affected channel(s) may be blown. The main fuses are located in the line filter assembly and are accessible when the amplifier’s top cover is removed.

• The audio module’s housekeeping supply is not working on the affect channel(s). This is a rare failure because the housekeeping supply has very reliable protection against short circuits and other possibly destructive situations. Without its housekeeping supply, though, the audio module cannot signal the power supply module to turn on.

Protect LED lit

• If the Protect LED lights steadily, without interruption, the power supply module is not working.

• If the amplifier is hot, it has probably overheated and will stay in protect until it cools down to a safe temperature.

Amplifier endlessly cycles on, into protect, and then off, and over again

• There is a defect in the audio module—probably in the output circuitry—that prevents the power supply module, as it starts up, from reaching its proper rail voltages or places DC on the output. When this happens the channel immediately switches into protect, and then the power supply resets and tries to start again.

Technical Service Manual 23 PowerLight 6.0 II, PowerLight 6.0

PFC

, and PowerLight 9.0

PFC

3.3 Further troubleshooting

This procedure allows you to further isolate the problem and determine which board or module is defective.

Start at zero volts

1. Turn the variable transformer to zero and turn the amplifier off.

Open the amplifier

2. Remove the top cover of the amplifier. See the Servicing chapter for instructions and diagrams.

3. Check the continuity of the two main fuses, located at the top of the line filter assembly near the front of the amplifier. Replace any that are open.

Ramp up the AC voltage

4. Turn up the AC voltage to about 30 volts (120-volt model) or 60 volts (230-volt model).

5. Using pliers, pull the connectors for the two housekeeping supply wires off of the audio module of the affected channel. Measure the voltage between the wires. It should be approximately 40 volts DC. If the voltage is significantly lower or is not there at all, there may be a problem with the portion of the housekeeping supply that is on the line filter assembly.

6. If the voltage is good, reconnect the housekeeping supply wires.

7. Disconnect the latching connector on the cabling that goes to the input board. If the channel now starts up, then the problem was on the input board—perhaps a defective op amp; replace or repair the input board.

8. If disconnecting the input board did not make the channel start up, reconnect it and turn the amplifier off.

9. Disconnect the power supply control ribbon cable from the 8pin header on the audio module. Attach the power supply remote controller (See the section on servicing power supplies in Chapter 2) to the ribbon cable.

10. Loosen the screw terminals of the five power supply wires at the front of the audio module. Remove the wires from the terminals and make sure they are arranged so none of them will short out against anything.

11. Turn switch S1 on the remote controller to amplifier on. The LED on the remote controller should glow green.

12. Increase the AC voltage to 65 volts (120-volt model) or 130 volts (230-volt model).

13. Measure the voltages on the supply wires 1 through 4, using wire 0 as a reference.

and turn the

24 QSC Audio Products, Inc.

TD-000083-00

4. Parts

4.1 Semiconductor package descriptions and pinouts

Legend:

A = anode; B = base; C = collector; D = drain; G = gate; K = cathode; S = source

IC-000024-00

Controller, PWM, SG3525AN; 16-pin DIP

INV. INPUT

NON-INV. INPUT

SYNC

OSC. OUTPUT

DISCHARGE

SOFT START

1 2 3 4

7 8

RE F

OUTPUT B

GROUND

OUTPUT A

SHUTDOWN

COMPENSATION

IC-000031-00

Opto isolator , 4N30; 6-pin DIP

1 2 3

6 5 4

IC-000047-30

Comparator , dual, LM393; 8-pin SMT

OUTPUT A

INVERTING

INPUT A

NON-INVERTING

INPUT A

GND

1 2 3 4

V+

OUTPUT B

INVERTING

INPUT B NON-INVERTING

INPUT B

IC-000049-00

Opto coupler , HCPL2200; 8-pin SMT

ANODE

CATHODE

1 2 3

SHIELD

GND

TRUTH TABLE

(POSITIVE LOGIC)

LED ENABLE OUTPUT ON

OFF

H H

L L

Z Z H L

IC-000042-00

Voltage regulator, +5V, MC7805CT ; 3-pin TO-220

GROUND

OUTPUT

GROUND

INPUT

IC-000046-30

Op amp, dual, TL072; 6-pin SMT

IC-000048-30

Op amp, dual, MC33078; 6-pin SMT

OUTPUT A

INVERTING

INPUT A

NON-INVERTING

INPUT A

V-

PowerLight 9.0 Parts lists

1 2

3 4

PFC

, PowerLight 6.0

V+

OUTPUT B

INVERTING

INPUT B NON-INVERTING

INPUT B

PFC

, PowerLight 6.0 II Service Manual 25

IC-000050-00

Opto coupler , 6N137; 8-pin DIP

IC-000051-00

Opto isolator , MOC8101; 6-pin DIP

1 2 3

6 5 4

IC-000053-30

Timer, dual, LM556; 14-pin SMT

Comp.

Flip-flop

14 13 12 11 10 9 8

DISCHARGE

THRESHOLD

CONTROL VOLTAGE

RESET

OUTPUT TRIGGER GROUND

1 2

Comp.

3 4

Flip-flop

5 6

Comp.

IC-000054-30

Comparator , quad, LM339AM; 14-pin SMT

DISCHARGE THRESHOLD CONTROL VOLTAGE RESET OUTPUT TRIGGER

IC-000057-30

Counter, ripple, 74HC4024, SMT; 14-pin SMT

GND

6 7

13 12

Q0 Q1

IC-000059-00

T op switch, TOP202; TO-220

IC-000235-00

T op switch, TOP224; TO-220

OUTPUT 2 OUTPUT 1

V+

INPUT 1-

INPUT 1+

INPUT 2-

INPUT 2+

1 2

3 4 5

6 7

OUTPUT 3

OUTPUT 4

GROUND

INPUT 4-

INPUT 4+

INPUT 3-

INPUT 3+

IC-000055-30

Regulator, power factor, UC3854B; 16-pin SMT

GND

PKLMT

CAO

ISENSE

MOUT

IAC

VAO

VRMS

2 3 4 5 6 7 8

16 15 14 13 12 11 10 9

GTDRV VCC CT SS RSET VSENSE ENA VREF

IC-000056-30

Driver , MOSFET, TC4427; 8-pin SMT

NC IN A GND IN B

2 3 4

2,4 7,5

8 7 6 5

NC OUT A V

OUT B

DRAIN

SOURCE

CONTROL

IC-000060-00

Oscillator, clock, 6.000 MHZ; 4-pin DIP

GND

OUT

IC-000063-30

Op amp, quad, MC33074; 14-pin SMT

OUT 1

INV. 1

NON-INV. 1

NON-INV. 2

INV. 2

OUT 2

1 2 3 4

5 6 7

OUT 4

INV. 4

NON-INV. 4

NON-INV. 3

INV. 3

OUT 3

26 QSC Audio Products, Inc.

TD-000083-00

IC-000064-00

Driver , MOSFET, 4452BN; 8-pin DIP

GND

3 4

OUT

GND

IC-000067-30

Differential amplifier , dual, CA3054; 14-pin SMT

1 2 3 4 5 6 7

13 12

11 10

NCSUBSTRATE

9 8

IC-000072-OP

Op amp, dual, TL072; 8-pin DIP

OUTPUT A

INVERTING

INPUT A

NON-INVERTING

INPUT A

V-

1 2 3 4

V+

OUTPUT B

INVERTING

INPUT B NON-INVERTING

INPUT B

IC-000073-30

T ransconductance op amp, DUAL, LM13600M; 16-pin SMT

AMP BIAS INPUT A

DIODE BIAS A

NON-INVERTING

INPUT A

INVERTING INPUT A

OUTPUT A

BUFFER INPUT A

BUFFER OUTPUT A

1 2 3 4

V-

6 7 8

AMP BIAS INPUT B

DIODE BIAS B

NON-INVERTING

INPUT B INVERTING INPUT B

OUTPUT B

V+

BUFFER INPUT B

BUFFER OUTPUT B

IC-000070-30

Voltage reference, +2.5V, LM4040DIM3X-2.5; 3-pin SOT-30 (SMT)

IC-000071-00

Sensor, temperature, LM35DZ; TO-92

+VSV

GND

OUT

IC-000085-00

Voltage regulator, +12V, LM2937ET -12, low drop out; TO-220

GROUND

OUTPUT

GROUND

INPUT

IC-000133-30

Comparator , single, LM311; 8-pin SMT

GROUND 1

NON-INVERTING

INPUT

INVERTING

INPUT

1 2 3 4

V-

8 7 6 5

V+ OUTPUT

BALANCE/ STROBE

BALANCE

PowerLight 9.0 Parts lists

PFC

, PowerLight 6.0

PFC

, PowerLight 6.0 II Service Manual 27

IC-000134-00

Driver , MOSFET, IR2110; 14-pin DIP

QD-000024-QD

Diode Zener, 6.2V, , 0.25W, DZ901116G, DO-35

COM

1 2 3

4 5

14 13

LIN

HIN

PD-000036-30

Power supply signal management, GAL16V8, PL9.0

This device must be programmed by QSC before installation.

I I I/CLK Vcc I/O/Q

232019

I GND I/OE

I/O/Q I/O/Q

13119

I/O/Q

PFC

and PL6.0

PFC

QD-000042-00

Diode rectifier ultrafast, 400V, 3A, MUR440, DO-201AD, 50 ns

QD-000052-00

LED green, T -1, diffused

QD-000022-QD

Diode Zener, 18V, 1W, 1N4746A, DO-41

QD-000053-00

LED yellow, T-1

QD-000023-QD

Diode Zener, 180V, , 1.5W, 1N5955A, DO-41

QD-000054-00

LED red, T -1

QD-000047-00

Diode Zener, 200V, , 1.5W, 1N5956B, DO-41

QD-000080-20

Diode Zener, 11V, 1W, 1N4741A, DO-41

QD-000159-20

Diode Zener, 47V, 1W, 1N4756, DO-41

QD-000159-20

Diode Zener, 47V, , 1W, 1N4756, DO-41

28 QSC Audio Products, Inc.

ANODE

CATHODE

TD-000083-00

+ 70 hidden pages