SERVICE BULLETIN INF9902 - APRIL 1999
This is considered a Minor repair
To: All Infinity Service Centers
Models: BU-80/HTS-10 (rev. "A,B")
Subject: Check Solder Joints in Event of Failure
Some performance related complaints in the BU-80 powered Subwoofers may be caused by cold solder
connections between the 28 pins of the Power Amp Module and the main circuit board. When troubleshooting,
failure to check these joints can result in erroneous conclusions or wasted time.
In the event you receive a Subwoofer with the complaints “Dead, or No Output, or Motorboating (Oscillation)”,
perform the steps listed below first before any further troubleshooting takes place:
1) Unplug all cables, lay the subwoofer on a padded surface.
2) Remove all Philips screws around the outer perimeter of the amplifier faceplate.
3) Remove amplifier assembly; you should be able to remove the amplifier far enough out of the cabinet to
service it without removing the woofer wires.
4) Locate the Power Amp Module; it is the large gray component with a metal case. On the solder side of the
circuit board are the 28 soldered connections to the Module.
5) Regardless of whether you can visibly see breaks in any of the connections or not, carefully re-solder all 28 pin
connections, adding 60/40 rosin core solder. Take care not “bridge” any connections on the board with solder.
6) Inspect the solder joints to the main filter capacitors C1 and C2 on the main PCB and re-solder if needed.
7) Replace the amplifier assembly back into the cabinet; replace the screws.
8) Test the unit by applying a signal from a music source, adjust the volume to a moderate level and confirm the
original problem has been corrected.
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Amplifier/Subwoofer BU-80/HTS-10
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