MC-30 Can Capacitor

Discussion in 'McIntosh Audio' started by kcdonahue, Feb 11, 2018.

  1. kcdonahue

    kcdonahue AK Subscriber Subscriber

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    Bel Air MD
    Looking for some input,

    I just recapped a dead MC-30 and had a CE 100uf/100uf 500V cap laying around that I used to replace the old unserviceable can. I fired it up and the voltages look good but the rectifier is quite noisy.

    After thinking about it, I am a little concerned about exceeding the max cap value from the 5U4GB with the 100uf. Of course I did not measure the power transformer HV windings when I had it apart to calculate the peak plate current...

    Any thoughts or experience before I head back to the bench?

    I haven't tried swapping the tube yet so it may just be the tube...

    Thanks,

    KC
     
    Last edited: Feb 11, 2018
  2. Brice

    Brice AK Subscriber Subscriber

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    Location:
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    Max is 40uf I believe. You're going to stress the rectifier.
    Use an Authenticap KTL25 with 40uF @550V off the rectifier and the rest for the down stages (80 30 20).
     
    x3workshop likes this.
  3. x3workshop

    x3workshop AK Subscriber Subscriber

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    Agree with Brice here. You've exceeded the recommended cap value by 60uF. Use the Authenticap KTL25. Much better than the CE version and it's closer in physical size to the original.
     
  4. dewickt

    dewickt Will fix about Anything

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    Location:
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    Been using the 100x100 in MC30 and MC60 amplifiers for over 20 years and never had a problem !! (over 100 amps.)
     
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  5. mcgjohn

    mcgjohn Member

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    53

    May seem obvious, but are you sure the rectifier tube is still good?
     
  6. x3workshop

    x3workshop AK Subscriber Subscriber

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    Location:
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    This is surprising to me. All the data sheets spec 40uF as max cap value for that rectifier. Why is that not the case here?
     

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