Question about Velodyne FSR-12 Speaker

2 Answers

My FSR12 oscillates a 1 second intervals with full woofer excursion. I have replaced the main amplifier 4040 chip and still have the problem. Both the 45 volt and 12 volt supplies are stable. Velodyne no longer supports the model but did send schematics. I was told that the accelermeter is attached to the voice coil and does not appear easy to get to without tearing off the dust cap. The ocscillation is not affected by disconnecting the 4 condutor flat cable to the accelerometer. Might the amplifier go full voltage while waiting for feedback from the accelerometer? Is there anywhere to buy an accelerometer for this model? Thanks in advance for your thoughts.

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  • fmk1x Aug 06, 2010

    FSR-12 Speaker
    My FSR12 oscillates a 1 second intervals with full woofer excursion. I have replaced the main amplifier 4040 chip and still have the problem. Both the 45 volt and 12 volt supplies are stable. Velodyne no longer supports the model but did send schematics. I was told that the accelermeter is attached to the voice coil and does not appear easy to get to without tearing off the dust cap. The ocscillation is not affected by disconnecting the 4 condutor flat cable to the accelerometer. Might the amplifier go full voltage while waiting for feedback from the accelerometer? Is there anywhere to buy an accelerometer for this model? Thanks in advance for your thoughts.

  • Scott Kohn Dec 31, 2011

    I have a similar problem. The sub has a strong white noise despite input and volume and cutoff. If I disconnect the accelerometer I get full excursions of the driver. My +45V rail is pretty close to 45V and has less than 0.1V AC ripple when checked without input signal and the speaker and accelerometer disconnected. This section of the PCBA is dark and charred looking and C17 is measuring 1.7kOhm (when it should be a 10uF cap). Hoping that if I replace this cap and maybe some of the other nearby components it will work properly again.

  • Scott Kohn Jun 23, 2012

    I ended up bypassing the feedback portion of the circuit. The audio quality is acceptable. for now. I cut a resistor lead and soldered in a jumper wire to do this.

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Hi


fmk1x,

Sometime it also ( accelerometer) get loose


Another trick , is to isolate the Main Amp Input to the Preamp

output and check.


• While it is disconnected , Measure the Offset voltages on the

Main Amp Out ( without the woofer connected ).


Here are sample schematics:


My FSR12 oscillates a 1 - d7bd1a6.jpg


and another one


c2e0c2a.jpg



Source:

[PDF] STK4040V AF Power Amplifier (Split Power Supply) (70W min, THD ...



A good amp never produce an over of 0.7V on its output.

Posted on Aug 06, 2010

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  • Rommel Cana
    Rommel Cana Aug 06, 2010



    post the DC offset value , to help you further

  • Rommel Cana
    Rommel Cana Aug 07, 2010



    • Have you tried disconnecting the Main input? just to see the results

    If still does , then Check every components on the Main Amp

  • Rommel Cana
    Rommel Cana Sep 02, 2010



    I just hope these answers your problem.

    thanks for choosing Fixya for assistance!

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Hi! You may want to inquire at audiolab.com regarding the accelerometer. Have a nice day!

Posted on Aug 05, 2010

  • dj_relly999
    dj_relly999 Aug 06, 2010

    Hi! HOw was it?

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