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Naim chrome bumper issue, Help

Discussion in 'audio' started by KiwiMike, Aug 31, 2020.

  1. KiwiMike

    KiwiMike Member

    Hi there,
    My nac 225 ( very similar to nac42 ) has developed a problem, when i turn on the power amp there is a delay of approx 5 seconds then a split second hum then a pop and then a hiss from the left channel.
    This hiss is at a set level not effected by volume control, selecting different sources does nothing the hiss is still there .
    Theres no hiss when pre is unplugged from power amp. But the audio is perfect once its turned up a bit.
    Hope some one can help
    Regards
    Mike
     
  2. Gervais Cote

    Gervais Cote Predator

    How old is the preamp and does it still have the original capacitors ?
     
  3. Craig B

    Craig B Re:trophile

    I suspect that @KiwiMike is referring to an NZ built NAC225, in which case very old.

    Mike,

    Assuming that you also have the Kiwi built NAP125 amp, then both are likely to be well overdue for a service. Typically, this involves replacing capacitors, from the large electrolytic power supply ones in the NAP through to the tiny tantalum ones within the NAC. A good technician will also ascertain the condition of the potentiometers, switches, and sockets, as well as check/reset bias current within the NAP.

    A service represents a good investment relative to what it might cost to replace with something newer that is able to compete on performance grounds, let alone be as reliable and serviceable over the long term.

    Craig
     
    Last edited: Aug 31, 2020
  4. stevec67

    stevec67 pfm Member

    Sounds like it needs a capacitor service, any competent repairer can do this.
     
  5. Minio

    Minio Not flakey and never soggy ...

    It sounds like my preamp the way Kiwi is describing it.

    The tantalums had to be replaced and it is fine again.
     
    stevec67 likes this.
  6. KiwiMike

    KiwiMike Member

    Thanks for your feedback, i will replace the tantalums tomorrow if that doesnt work i will put aside the mother board for now and try one of those clone boards.
    Mike
     
  7. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    All I can add to the above advice would be that it could be risky to use it in this condition
    ... The hisses pops etc could be related to oscillation and there is a possibility off a blown tweeter or output transistor. The latter could take out a woofer...
     

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