Question about Yamaha P4500 Power Amplifier 2-Channel

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Yamaha P-4500 Hello guys here, I have just got across of this nice amp P-4500 with no powering up problem.Few gentle touches inside and I know there is problem with primary on power transformer.Have no idea how does it happened, because there is nothing burned or smelly, but primary is shortened.Would be possible, if someone may drop here the values for this transformer ? Voltage,resistance.Many thanks Radek from New Zealand

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  • rpiskula Sep 12, 2008

    Hi robotek,

    Yes it is toroidal transformer with outer diameter ca 18 cm and very heavy, would guess over 7kg.
    And the symptom is exactly as you said, it does blow fuses. More accurately said one of two, probably the weakest one.
    I have removed transformer from chassis and disconnect all wires. Then I was able measure resistance on primary which was around 1.8 ohms.That is pretty low for 650 VA transformer I think.



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Hi radek

If it is a toroidal,they have a nasty habit of going shorted turns on the primary. Is it blowing fuses? Let me know

ex In'gill ;)

Posted on Sep 12, 2008

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If it is a toroidal,they have a nasty habit of going shorted turns on the primary. Is it blowing fuses? Let me know

Posted on Aug 01, 2010

  • toto mm Aug 01, 2010

    If it is a toroidal,they have a nasty habit of going shorted turns on the primary. Is it blowing fuses? Let me know


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