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    Speaking of Mk IV problems

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    corndog71

    Posts : 444
    Join date : 2013-03-19
    Location : It can get windy here

    Speaking of Mk IV problems

    Post by corndog71 on Mon Jul 14, 2014 12:54 pm

    I sold my pair of newer MkIV amps (Dynakitparts) with curcio upgrades to a buddy of mine and he recently developed a problem with one of them. He's tried with and without tubes, checked for shorts and found none but the amp still blows the fuse upon flipping the power switch. We suspect the transformer went bad. Is there a way to check the PT for internal shorts?

    Bob Latino
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    Join date : 2008-11-26
    Location : Massachusetts

    Re: Speaking of Mk IV problems

    Post by Bob Latino on Mon Jul 14, 2014 1:10 pm

    If you pull all the tubes out of an amp then turn the amp ON and it blows a fuse instantly, then it is almost certain that the power transformer is bad. To double check that the power transformer is bad > remove it from the amp. Now separate all the wires so that they don't touch. Run your AC into the two BLACK wires through an inline fuse on one side of the AC line. If the amp blows the inline fuse instantly, then the power transformer is bad. You can't really say which winding is bad but one of them has to be bad. The most likely suspect is the high voltage winding (the two RED wires that go to pins 4 and 6 on the rectifier tube socket).

    Bob

    corndog71

    Posts : 444
    Join date : 2013-03-19
    Location : It can get windy here

    Re: Speaking of Mk IV problems

    Post by corndog71 on Mon Jul 14, 2014 5:10 pm

    Thanks, Bob.

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