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Naim Nap 250 problems

Discussion in 'd.i.y.' started by takemine1, May 20, 2019.

  1. takemine1

    takemine1 pfm Member

    What would cause a Naim 250 to stop working..
    Having sold this to another fellow fish, he stated within a few days the thermal protection was triggered and now is not working..
    It was serviced in 2015 and was working fine until he got it..
    His other stuff is a Naim 82 pre and a hicap..
    Source LP 12..
    He had a 180 which he used as a replacement and which is working.
    Hmmmm..
    Any thoughts..
     
  2. coltrane

    coltrane electrobaroCKjazzer

    just my 2 cents> wasn't the fuse blown at the event (maybe to high a volume, and a resulting rise in temperature that caused the amp shut down) and now the amp's simply lacking in juice from the wall outlet? perhaps just an easy fuse replacement...
     
  3. colasblue

    colasblue pfm Member

    If it's a thermal issue it should come back on when it cools down.

    If it hasn't then it could be a faulty thermal trip which hasn't re-set or something else.

    Very unlikely that a thermal shut down on its own would blow the fuse.

    obviously try fuse replacement first but if it's not that it needs looking at by somebody with at least basic diagnostic ability.

    Where is the amp now, happy to help if its somewhere near me.
     
  4. neiljadman

    neiljadman Senior Member

    Not many things would shut it down simultaneously in both channels, just the thermal trip and mains fuse as far as I can see.
    • Check the mains fuse first
    • What are the speakers. IIRC the 250 is sometimes sensitive to very low impedance (e.g., Linn Saras)- causing overheating and the thermal trip to go. But as stated is should restart on cool down.
    • If drawing a massive current perhaps both of the trips in the regulator boards have gone too. But I have never seen it.
    Anyway start at the front end and measure voltage along the power rails from inlet to the amp boards, at least you will find out where int he amp the problem is:
    • Is the fuse intact?
    • Is the full 57v getting to the voltage inputs on the regulator boards?
    • Are the regulator boards putting out the correct rail voltages too?
     
  5. hp1

    hp1 pfm Member

    I will take a look at it for You if that helps.
     
  6. MJS

    MJS Trade: Consultant at WH Audio

    Do these simple checks first, no need to remove case or anything.

    Does the logo light up? If not then check fuse in both the mains plug and the IEC socket. If they're fine then there could be a switch issue - I've not seen the thermal trips die. A multimeter in ohms should see a near-short between L and N on the mains plug when switched on and disconnected from mains.

    Got light but no sound? Easy check if you have a multimeter is to look for DC offset on the speaker terminals. If the amp is working fine there should be a small, between -20 and +20mV, offset at the terminals. If you have exactly zero volts here then the trips have fired on the power supply. That would need further investigation.
     
  7. takemine1

    takemine1 pfm Member

    Thanks for all your advice and responses.
    Now sorted.
     
    Spike55 likes this.
  8. Dowser

    Dowser Learning to bodge again..

    And solution was...? :)
     
    Spike55 likes this.
  9. joe9407

    joe9407 actress/activist

    dude, you've totally left us hanging here.
     
  10. peterm

    peterm pfm Member

    I seem to notice an increasing trend for people to ask for advice to help them solve a problem and, having received such advice, to simply disappear from the thread leaving us all wondering what the cure really was.

    Not only does it seem rather ignorant but it doesn't help anyone else who, having the same problem, would like to know what the eventual cure was from all the suggestions received.

    I'm looking (in vain so far) for a response to a couple of threads on the Audio forum which have had many replies from members, including me, but no feedback regarding the outcome.

    Makes you think twice about offering advice to those individuals should they expect assistance in the future!
     
    Spike55 likes this.
  11. cctaylor

    cctaylor pfm Member

    Learning and teaching is a two way process.

    Our curiosity has been stimulated and we have been left wanting an answer.

    Even if it was something simple like a fuse, I'm sure we have all been there before.
     
  12. timH

    timH Senior Moment Member

    Maybe the solution was so simple they’re embarrassed to own up?
     
  13. takemine1

    takemine1 pfm Member

    Hi..Sorry about that as Ive been away.
    The simple answer is I don't know..
    The new owner who for what ever reason didn't want to send the 250 bk to me and has decided to have an audio engineer fix it.
    If I get any more information I will of course pass this on..
     
  14. peterm

    peterm pfm Member

    Apologies if I tarred you with the same brush as some others who have "been away" for months or years!

    Re reading your original post I realised that I'd forgotten you had sold the 250 and so you couldn't have tried the suggested remedies first hand anyway!
     
    cctaylor likes this.

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