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Troubleshooting: amplifier Musical Fidelity A1

Discussion in 'Electronic Repair' started by Sala Massimo, Dec 8, 2003.

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  1. Sala Massimo

    Sala Massimo Guest


    I am the happy owner of one A1 amplifier, bought in 1991.
    It is 20 Watt class A amplifier, build around four MOSFET:

    In the last months the A1 started to malfunction, the volume knob works very
    bad: when I turn the knob I hear strange noise ("shhh shhh" as there is sand
    inside the knob, and also some "crack") and the volume output isn't in
    accordance with the knob position.

    I took the unit to repair, but they said me they cannot because they haven't
    the potentiometer.

    I ask you:
    1) is really the pot the culprit ?

    2) where can I found one (or two) spare parts?
    It is a Alps 0071 50KAX2 (I cannot measure the value because it is

    3) by the way, do you know which are the exact final transistors?
    I found on newsgroups many codes:
    original: A1 N8915 and A1 P8919
    poor quality? 2N3442 and 2N5876
    good ? Motorola MJ15003 & MJ15004

    My unit (model A1 X) has these transistors:
    A1N9020 A1N9034
    A1P9022 A1P9018
    I don't understand why are there four different codes instead of two exact

    ciao, Massimo
  2. Guest

    Pricy, huh? :))
    Sounds like bad contacts in that knob...
    I guess that isn't just a simple pot, more like a shunt... Musical Fidelity
    is high-class audiophile company, so I guess they use high-quality shunts
    for volume knobs...
    Don't know... You could contact Musical Fidelity and ask them to help you
    find the right service-shop where you can repair your unit... Or simply find
    some service shop from some audiophile genious... Local audiophile stores
    are best thing to start... :)
    Oh, neighbour! :)))) Greetings from Fiume, Croatia... ;)

    "Sravnjens li bananau crtu ?" upita Milosevica podjebava cizmao zmice.
    "Nisam ja nikog bombardiro !" rece cizma gladi "Ja samo stolo njise humanitaranm !" By runf

    Damir Lukic,
    a member of hr.comp.hardver FAQ-team
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