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Service Bulletin
Passionate About Sound
Title:
Handling PLC Power Supply Failures
Bulletin #:
PLC0019
Issue Date:
19 November 2013 (original release 12 November 2013)
Products Affected: CX, DCA, PLX, and PL3 Series power amplifiers
Revision:B
Production Range: All
Description
The switch-mode power supplies used in the CX, DCA, PLX, and PL3 Series (i.e., the PLC platform) power amplifiers are high-performance
circuits meant to provide strong and stiff low-ripple voltage rails for the amplifier circuitry through low-loss IGBTs, power transformer, and
rectifiers. Although they are designed to be highly reliable, some random circumstances such as device defects may sometimes cause
failures that the supply control circuits cannot avert.
These failures will usually cause catastrophic damage to the insulated gate bipolar transistors (IGBTs) that do the actual high-frequency
switching that produces the >100 kHz AC for the power transformers. The damage will almost always extend also to the components that
control, generate, and deliver the drive pulses to the IGBT gates.
In lower-power amplifier models such as the CX302 or DCA1222, the components may sometimes fail without also destroying traces on the
circuit board; in these situations, the board can be cleaned up and the components replaced using the PLC Power Supply Restoration Kit
(QSC part # SG-000060-00). If the printed circuit board (PCB) is burned or deteriorated, or traces have been vaporized, as usually happens
in the higher-power models such as PLX3602, CX1102, DCA3422, or PL340, the whole PCB module must be replaced. This bulletin includes
a table listing all the PCB modules’ QSC part numbers. Please note that the modules are manufactured for specific AC mains voltages and
therefore have specific part numbers for not only each model but each operating voltage.
Symptoms
PLC amplifiers that have suffered power
supply failures will be completely dead and
unresponsive when plugged into AC mains
power and turned on. They may have a
smoky or burned smell.
At the moment an amplifier’s power supply
fails, the distinctive indicators are popping sounds from within the chassis, often
accompanied by sparks, smoke, or both,
followed by complete inoperability.
Instructions
If a PLC amplifier exhibits the above
symptoms, remove the bottom cover and
inspect the power supply section of the PCB
module.
Component damage only; PCB
undamaged
Figure 1. When the power supply failure damages the printed circuit board, the whole PCB
module must be replaced.
If the PCB is undamaged and all the traces
are intact, clean any carbon deposits off
the board and replace the components with new ones from the PLC Power Supply Restoration Kit (QSC part # SG-000060-00). Follow the
directions provided with the kit. Always make sure the control, timing, and gate drive circuits work properly before you install the IGBTs at
Q96 and Q97.
continued on next page Ü
PLC0019 rev. B
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Please note that the PLC Power Supply Restoration Kit is not appropriate for the PL380; it uses very different IGBTs (Q68 and Q69) that
have insulated backs and use transformer-coupled gate drive.
Also, inspect diodes D70 and D71 (or D68 and D69 in the PL380); if they are UF5404 types, or you cannot tell because the identifying
marks are unreadable, remove them and install MUR440 (QSC part # QD-000042-00) diodes in their place.
Component and PCB damage
The the PCB is damaged—e.g., the substrate is burned, one or more copper traces is or are blown, etc.—do not spend any time replacing the
individual components. Replace the amplifier’s PCB module instead and scrap the old one. See Table 1 for the part numbers. QSC TSG will
process any billing or warranty claims appropriately.
You may notice that amplifiers manufactured in a certain date range—July through October 2012 (0712xxxxx through 1012xxxxx), inclusive—
might exhibit a slight statistically higher rate of failure. These amplifiers were built with UF5404 diodes instead of MUR440 at locatons D70
and D71 (or D68 and D69 in the PL380).
Table 1. PLC Platform Amplifier PCB Module Part Numbers
Operating voltage:
100 V
120 V
230 V
PLX Series
CX Series
DCA Series
PL3 Series
2
PLX1802
WP-001803-01
WP-001803-00
WP-001803-02
PLX2502
WP-002503-01
WP-002503-00
WP-002503-02
PLX3102
WP-003103-01
WP-003103-00
WP-003103-02
PLX3602
WP-003603-01
WP-003603-00
WP-003603-02
CX302
WP-000071-01
WP-000071-00
WP-000071-02
CX502
WP-000101-01
WP-000101-00
WP-000101-02
CX702
WP-014001-01
WP-014001-00
WP-014001-02
CX902
WP-018001-01
WP-018001-00
WP-018001-02
CX1102
WP-011030-01
WP-011030-00
WP-011030-02
CX302V
WP-000061-01
WP-000061-00
WP-000061-02
CX602V
WP-012001-01
WP-012001-00
WP-012001-02
CX1202V
WP-024001-01
WP-024001-00
WP-024001-02
CX254
WP-000255-01
WP-000255-00
WP-000255-02
CX404
WP-000405-01
WP-000405-00
WP-000405-02
CX204V
WP-000205-01
WP-000205-00
WP-000205-02
CX168
WP-000169-01
WP-000169-00
WP-000169-02
CX108V
WP-000369-01
WP-000369-00
WP-000369-02
DCA1222
WP-001223-01
WP-001223-00
WP-001223-02
DCA1622
WP-001623-01
WP-001623-00
WP-001623-02
DCA2422
WP-002423-01
WP-002423-00
WP-002423-02
DCA3022
WP-003023-01
WP-003023-00
WP-003023-02
DCA3422
WP-003423-01
WP-003423-00
WP-003423-02
DCA1644
WP-001645-01
WP-001645-00
WP-001645-02
DCA1824
WP-001825-01
WP-001825-00
WP-001825-02
PL325
WP-032501-01
WP-032501-00
WP-032501-02
PL340
WP-034001-01
WP-034001-00
WP-034001-02
PL380
WP-038001-01
WP-038001-00
WP-038001-02
PLC0019 rev. B
Contact information
Technical bulletins and other service documents are available for download from www.qscservice.com. If you need any further
information regarding this service procedure, please contact QSC Technical Services at the addresses or numbers below.
1-800-772-2834 (within USA only)
+1 (714) 957-7150
Fax:
+1 (714) 754-6173
Skype:qscaudio
E-mail:
[email protected]
Web sites:
www.qsc.com (product info/support)
www.qscservice.com (product service and service center support)
www.qscparts.com (on-line accessory and replacement component sales)
Postal and parcel address:
QSC Audio Products, LLC
Technical Services Group
1665 MacArthur Blvd.
Costa Mesa, CA 92626 USA
Telephone:
PLC0019 rev. B
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