PLX 3602 intermittent problem

Moderators: Cameron Shoffner, Christian Cook, Kirk Fyvie, Martin Barbour, Gary Evans_QSC, QSC-Dale Sandberg

Wed Jul 08, 2015 11:33 am

  • I have a PLX3602 that periodically malfunctions. It will work fine for awhile and then it shuts down and starts power cycling on and off. I shut it down and unplug it for 5 minutes or so, and then it works fine again.

    I have so far been unable to reproduce the problem in the shop, but I am reluctant to send it out on gigs.

    Any help or suggestions would be much appreciated.
    Thanks,
    Paul
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Wed Jul 08, 2015 3:47 pm

  • Do you have a voltmeter or other means of monitoring the AC mains voltage at the outlet the amp is plugged into? An extremely low AC mains can cause problems similar to that.
    Bob Lee
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Thu Jul 09, 2015 9:57 am

  • The first time it happened was in a venue we regularly have gigs, and was the only piece of gear malfunctioning. The second time it was hooked up to a power distro that was fed from a generator, (I always meter a generator before connecting any gear) and again nothing else was malfunctioning. So I don't think its the AC power.

    I have also now found out that it makes audible pops and crackles in the speakers when the amp is jostled slightly.
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Thu Jul 09, 2015 10:12 am

  • If the AC voltage drops during the performance, which can happen when there is heavy current demand, the amp is likely to exhibit those symptoms. That's still an open question in this situation, and a very likely culprit.

    If you use AC extension cables, making sure you don't use cables that are undersized or excessively long will help prevent this happening. Also, don't run too much stuff on each extension cable; sometimes you might have to run two or more extension cables together back to the power source, especially if you have multiple devices that tend to draw current heavily.

    Check whether the crackles come from the input connectors being wiggled. Input (and sometimes output) connections are common places where this symptom arises. Cleaning the jacks and connectors with a lubricating cleaner such as Caig Laboratories DeOxit spray will often alleviate the problem.
    Bob Lee
    Technical Communications Developer
    QSC, LLC
    Fellow, Audio Engineering Society
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    "If it sounds good, it is good." —Duke Ellington
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    Bob Lee
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    Location: Costa Mesa, California



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