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Naim Olive Hicap hum..

Discussion in 'd.i.y.' started by takemine1, Jun 18, 2019.

  1. takemine1

    takemine1 pfm Member

    Having dusted my Olive Hicap which I haven't used for some time, I find its developed a hum.
    Its noticeable and is not connected to the volume control.
    That is it doesn't vary to the volume control..
    Tried moving it away from the power amp. No change..
    I reconnected a CB power supply and thats ok..
    Any thoughts..
     
  2. MJS

    MJS Trade: Consultant at WH Audio

    Hum from speakers? Or more of a buzz? Do you get music?
    I suspect a tantalum cap has popped or gone leaky, pulling one of the rails down, said rail being relied on to un-mute the relay in the pre-amp thus leaving the power amp open circuit and hummy. That's the most common thing that happens to these.
     
  3. Jonathan

    Jonathan pfm Member

    Thought I’d had the same until I played with the intermittent connection on my cable
     
  4. takemine1

    takemine1 pfm Member

    Hi. Noise is from the Hicap not through speaker.
    Tried disconnecting all leads then turned on Hicap.
    No noise.
    Connected signal lead..No noise..
    Connected live lead to Pre and no noise..
    Hmmmm..
    Will leave it on and monitor..
     
  5. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    No doubt a noisy transformer then. It may vary with DC on mains or mains waveform quality when lots of TV sets are on etc. Harmless but won't fix itself...
     
    Last edited: Jun 20, 2019
  6. colasblue

    colasblue pfm Member

    This can sometimes be cured by loosening or tightening the securing bolts slightly and/or replacing the rubber pad the traffo sits on. It doesn't exactly cure the problem but it can be made a lot less noticeable sometimes.

    Failing that not all traffos suffer to the same extent so a last resort solution is to sell your HC and buy a different one.
     
  7. takemine1

    takemine1 pfm Member

    Thanks for the advice.
    Will check secure bolts.
    Noticed some times the noise from the Hicap .. some times loud and some times not so loud..
     
  8. colasblue

    colasblue pfm Member

    It's down to mains quality which varies over time and with what you and your neighbours have powered up.
     
  9. andrewsutton

    andrewsutton pfm Member

    Hi, consider a DC blocker. Google Rod Elliott ESP.
    There is an article and simple circuit there.
    Cheers Andy.
     
  10. nobeone

    nobeone pfm Member

    As others have said, assuming it is mains quality variations leading to DC on the large toroidal transformer causing it to hum you might consider this DC blocker group buy too https://pinkfishmedia.net/forum/threads/dc-blocker-gb-closing-soon.216403/page-3

    Obviously you could swap for a different PSU too that does not have such a large toroidal transformer, I assume Teddy Pardo PSUs don't do this. Might also be worth talking to Kit Ryan as I think RSL do a PSU based on a much less over engineered transformer so much less likely to hum.
     
  11. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Small ones can hum just the same...
     
  12. takemine1

    takemine1 pfm Member

    Thanks for the above.
    Thinking of renewing the capacitors..
    Any thoughts..
     
  13. nobeone

    nobeone pfm Member

    Sure but less and less likely no?
     
  14. nobeone

    nobeone pfm Member

    Not sure it will help the hum at all
     
  15. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Maybe... Can't say I've given it much thought but certainly I've known both big and small ones buzz.
     
  16. colasblue

    colasblue pfm Member

    Certainly won't cure the mechanical hum from the traffo but might make it sound better in other regards.

    If the CB one is fine then maybe get an older olive one with an H&F traffo and service that up or even swap the traffo's over.
     
  17. takemine1

    takemine1 pfm Member

    Ok. Opened the hi cap and found the strapping that hold the big caps in place was a little loose..
    Tightened this up and up to now its been quiet.
    Coincidence..
     

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