Service Bulletin - R.S. Engineering and Manufacturing

Service Bulletin
Title: Ouptut Summing for Redundant Operation
Bulletin #: RV0001 Issue Date: January 16, 2001
Models Affected: Rave 160 and 188 Bulletin Revision: B
Production Range: MM/YYYY–MM/YYYY
Description:
The RAVE 160/188 may be used in Master/Slave mode to provide a redundant audio output from the network. Connecting a BNC
cable between the SYNC Out of the Master unit and the Slave In of the slave unit causes the slave unit to remain in standby until the
network connection or AC power of the Master unit is lost. While in standby, the balanced outputs of the Slave unit are shorted
together and directed to ground through a single 100k ohm resistor to maintain noise integrity. If the audio outputs of the Master unit
are tied together with the audio outputs of the Slave unit a short circuit will result between the units causing a reduction of output
signal to near zero volts.
Units Affected:
RAVE units manufactured between the dates xx/xx and xx/xx may be modified to operate in redundant networks with the analog
outputs tied together. The serial number defines the month and year of manufacture. The first and second digits of the serial number
define the month of manufacture and the third and fourth digits define the year of manufacture (e.g. 1099xxxxx denotes manufacture
date of October 1999).
Symptoms:
When operated in slave mode with analog outputs tied together electrically, the audio output of the master unit is shorted to ground
through the audio outputs of the slave unit resulting in near zero audio level.
Instructions:
The following modifications will isolate each leg of the balanced outputs of the RAVE 160/188 and allow the Master and Slave units to
be tied together for correct redundant operation. Each channel must be modified in the same fashion to complete the unit.
Tools and materials required:
• #2 Phillips screwdriver
• Small sidecutters
• Needle-nosed pliers
• Exacto knife or similar cutting tool
• Fine-tip soldering iron
• Vacuum de-soldering station
• 16 1/8th watt, 1%, 100k ohm resistors
• DB-9 to 4-pin cable (wiring details are specified in this document)
• Audio Precision System 1 or equivalent measurement system.
• Oscilloscope
Procedure:
1. Disconnect the RAVE from AC and wait at least 10 minutes for internal voltages to bleed down.
2. Remove the top cover of the unit.
Note: Take anti-stati precautions. Wear a wrist strap attached to an appropriate ground while working on the unit to ensure static
protection.
3. Remove PCB from chassis.
4. For each channel a single trace connects pins 2 and 6 together on the output relay of the channel (see figure 1, typical). Locate
and mark each trace so that it is easy to find by inspection.
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5. De-solder and remove the output relays from channels 1,6 and 11. The trace that connects pins 2 and 6 on these channels is
located on the top side of the circuit board under the relays. Removal of the relays on channels 1,6 and 11 will expose the trace
so that it can be cut.
Note: Take care when removing the relays so as not to damage them or the circuit board. The use of a vacuum de-soldering station
is highly reccomended.
6. Cut the traces that were marked in step 4. Be careful not to cut too deeply, because the circuit board is multi-layered and
damaged traces in the middle layers of the PCB cannot be repaired.
7. Solder a 1/8th watt, 5%, 100k ohm resistor on the bottom of the circuit board between pin 6 of the relay and the 100k ohm
resistor connected to pin 2 of the relay (see figure 2, typical).
Note: Be careful not to short the new component to any nearby traces or other components. Also note that the resistors for
channels 1,6 and 11 can be placed in the same way as the other channels. It is only the location of the trace that is different.
8. When all of the new components have been attached to the circuit board use a multimeter to measure between the positive and
negative audio terminals of each channel. The measurement should be 200k ohms indicating that each leg has an independent
path to ground through its own 100k ohm resistor.
9. Measure between the ground and the positive terminal of each channel. This measurement should be 100k ohms.
10. Measure between the ground and the negative terminal of each channel. This measurement should be 100k ohms.
Figure 1. Typical trace location
Figure 2. Typical resistor placement
11. If all of the measurements are correct then the PCB can be reinstalled into the chassis. Note the orientation of the new components
and be careful not to snag them or short circuit them on any of the mounting hardware in the chassis.
12. Repeat the meaurements taken in steps 8 through 11.
13. Connect the RAVE units to a RAVE network and use a RAVE input unit to put audio onto the network. The audio can then be
picked up at the Master/Slave RAVE pair for testing purposes.
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13. With the audio outputs of two RAVE 160’s (or 188’s) tied together and the BNC cable between the SYNC out and Slave in of the
RAVE units, the audio signal should be clean and distortion free just as with a single unit by itself. This can be verified with the
Audio Precision System 1 and/or with the oscilloscope.
14. Make sure there are no foreign objects in the RAVE. Re-install the top covers and return the units to service.
Contact information
If you need any further information regarding this service procedure, please contact QSC Technical Services at the addresses or
numbers below. You can also order RAVE parts; to expedite processing please use the correct part number when ordering.
Telephone: 1-800-772-2834 (within USA only)
+1 714-957-7150
Fax: +1 714-754-6173
E-mail:
tech_support@qscaudio.com
Web Site: www.qscaudio.com (product info/support)
www.qscstore.com (on-line accessory and replacement component sales)
Postal and parcel address:
QSC Audio Products, Inc.
Technical Services Group
1665 MacArthur Blvd.
Costa Mesa, CA 92626 USA
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