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PLease Help..Pioneer A400 Electric Surge Popping Sound

Discussion in 'AV Receivers & Amplifiers' started by Sionster, Dec 30, 2004.

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  1. Sionster

    Sionster
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    Pionner A-400 Intergrated Amplifier

    Are there any Audio Technophiles here to guide me and my soldering iron in the right direction :thumbsup:

    Until a few weeks ago this amp has been delivering wonderous sounds to my ears. Now through no misuse, it is erratically delivering what I can only describe as an electrical surge 'popping' sound to the left speaker channel.
    This seems to occur randomly and in varying strengths from every few seconds to up to 20minutes or so. If the strength of this surge is strong enough the automatic protection unit shuts the amp down.

    I have already isolated the problem to the amp, in using entirely different speakers, CD player, cables and even switched off all the other electrical circuits in the house and tested on other mains sockets.
    I'm not one to give up on anything remotely repairable, and not afraid of soldering, it's just knowing where to look.

    I don't believe the power supply unit is at fault purely because this is only happening on one channel (Left). The fault is also unconnected to the input selector.
    The right channel is working perfectly normally.

    With the lid off, I cannot visibly see any damage/loose cables/dry joints or so forth, and neither can I see any visible sign when the problem occurs. It looks perfectly normal, but isn't well at all.

    Any advice you could give me would much appreciated...prehaps what to test, or what to look for.

    I Hope I'm not asking too much, but when the amp works....it's just to good to give up on!!..

    Many thanks for reading this far at least. Sion
     
  2. SolentSurfer

    SolentSurfer
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    Hi, I've owned the same A400 since 1990 and it still gives great service. Just ordered some Quad 11L's to replaced some very tired and battle scarred Mission 762's bought with the amp.

    The only problems I've had have been a crackly volume control which is the only thing I can put down to your problem. This is easily checked by moving the volume control with nothing playing. If it's crackly, get the lid off and spray with switch cleaner while turning back and forth.

    One other possibility that I've read about but not experienced is the main power supply caps which can wear out with a lot of use - I think these need pro replacement.

    Nothing else moves so either works or doesn't - so may be it's not your amp?
     
  3. mudan

    mudan
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    I'd say replace the PSU caps i.e. the big ones towards the back of the amp.
    The ones I now have in my A400 are of the Panasonic TSUP range which I bought from RS.
     

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