Pioneer SX-950-negative waveform clips at 26 watts.

Discussion in 'Solid State' started by EvanF, Jan 2, 2018.

  1. EvanF

    EvanF AK Member

    Messages:
    262
    Location:
    Kirkwood, Missouri
    DC offset is 180mV or so on each channel, cannot get it lower with the VR. The negative waveform soft clips at 26 watts, even after bias was set. What could be the issue?
     

     

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  2. inductor

    inductor Super Member

    Messages:
    1,522
    Location:
    uk
    both channels eh, regulated supply to driver stage volts low ?
     
  3. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
    21,608
    Location:
    Glen Burnie Md.
    The differential pairs are 2sa726's (Poor CHOICE!) Q1 thru Q4 on the Main Amp (AWH-050). Replace them with gain matched KSA992's. This will get your DC Offset down to a point where your pot should be able to set to 0.0v. KSA992's are cheap. Get enough to replace all of them in the 950 + 1/2 again for matching the diff pair's. These may also be 2sa763's which normally aren't a problem child. But here I'd go ahead and replace them with KSA992's, turned to face each other, and mounted so the faces are flat against each other for temp averaging. Hold them together with some heatshrink.
     

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