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Proton 520 Integrated Amplifier with quiet left channel

My Proton 520 Integrated amplifier has a problem.  The left channel is very quiet.  When I try to adjust the balance to compensate, I get static and it sometimes turns almost completely down.  The right channel plays fine, and the sound is great.
I have taken the cover off, and downloaded the schematics.  I am not sure where to begin testing things to see what caps, resistors or transistors I might need to replace.  I am new to amplifier repair, but I have a basic understanding of electronics, and I have completed some solder repairs before.
Thanks for any help!

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  • tjalbrecht Mar 30, 2009

    All were flushed and I still have this issue. I also completed the alignment portion involving the adjustment of variable resistors VR5 and VR6.

    I will also be testing a different set of speakers to see if that is the problem, but my speakers were giving me correct ohm readings.

  • tjalbrecht Mar 31, 2009

    Yes, I will check the voltage of the pre-outs later today and let you know what I find out.

  • francesco Feb 13, 2012

    ya, i have the same amp and same trouble, also spent money to rep but the problem is still there. Are you sure that a cleaning spray is enough? ty


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Flush all the switches and controls with De-Oxit D5 or better.
Then get back to me.

Posted on Mar 01, 2009

  • Scott Frye
    Scott Frye Mar 31, 2009

    That amp has a pre-out set of RCAs
    Is there some way you can check the level out of those before the power amp part of the unit?


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