About NAIM NAP 140 building

Discussion in 'DIY Discussion' started by bermek, Feb 24, 2020.

  1. bermek

    bermek

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    Hi people,
    I wanted to mention about a problem in my project with building a NAP140 amp clone.
    After putting everything together, I realized that although the sound is clean and satisfactory, one of the transistors (ztx653) and the resistor on its leg (I believe it was 2K2) on both channel boards are heating up seriously. I came to the point that I had to turn it of so it doesnt burn.
    Anyone can offer a solution to this problem, or ways to troubleshoot, and/or experienced a similar problem?
    Thanks in advance.
    Hakan
     
    bermek, Feb 24, 2020
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  2. bermek

    Gerontius

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    Hi Hakan,

    Have you got a suitable heatsink on the transistors? I seem to remember that Naim mount the power transistors on the chassis to keep them cool. As for the 2K2 resistors, you could try using ones with higher power dissipation.
     
    Gerontius, Apr 2, 2020
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  3. bermek

    field effect

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    You need to refer to the schematic, quite likely is the orientation of the ztx653 needs to be checked,
    in doubt refer to the data sheet for that transistor, referencing against the schematic.
     
    field effect, May 11, 2020
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  4. bermek

    bermek

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    Hi, the power tubes are perfectly cool. Ztx is a tiny plastic transistor.
    thanks for your suggestion though.

     
    Last edited by a moderator: May 18, 2020
    bermek, May 12, 2020
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  5. bermek

    bermek

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    I followed the schematics, except for a single transistor eqiuvalent, all parts are fidel to what printed circuit says. Orientation of ztx seems to be correct.

     
    bermek, May 12, 2020
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  6. bermek

    field effect

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    What voltage do you have on the power rails ? , I have read 34 V DC on each polarity is suggested.
    Check orientation of the two diodes at the base of TR6, and setting of VR1
     
    field effect, May 12, 2020
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