Help!! Kenwood KR 7070 Blowing main fuse!

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Jolly72, Aug 29, 2018.

  1. Jolly72

    Jolly72 New Member

    hey guys i was wondering if ya all could help me out.
    i'm a newbie at all this and have just started and would love to add restoring and collecting vintage receivers to my already vast pile of hobbies that irritate my wife to the point of "probable homicide"..... lmao.
    now i do know how to run a soldering iron and a multimeter, what i lack of course is know how and experience with troubleshooting.
    i got this receiver given to me and i would love to get it working again. the problem is it blows main fuse as soon as you turn it on, i've pulled the cover and visually inspected the components and don't see anything obvious like burnt resistors or wires nor do i smell anything burning.
    it's obvious that its got a dead short somewhere, my question is where do i start? what are the common checks to do to find the failed components? how would you go about fixing this?
    again i know just enough to be really dangerous and the only thing i really have are the basic tools, a very vague general knowledge of electronics and a desire to learn . if you guys think you can help me i sure would appreciate it alot.


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  2. hopjohn

    hopjohn Silver Face Subscriber

    Dallas, TX
    Understand a blown fuse means the device is drawing excessive current. While I'm not speaking to you directly, it must be said that many newcomers incorrectly think of a blown fuse as a cause not a symptom and will repeatedly replace it in effort to fix the problem when in reality they're only worsening it. Common amplifier failures that result in a blown fuse are in the output stage, driver stage, pre-driver stage, or biasing circuit. A failure upstream can cause failures downstream and vice versa so finding a single failed component and replacing it alone without checking everything else within the circuit may have it fail again. Blown fuses are not always an indication of a problem in the amplifier. The culprit/s could also lie within the power supply, like a failed rectifier for example. Furthermore, a dim bulb tester (DBT) is an invaluable tool for troubleshooting under these circumstances. If you do not own a DBT, search the many threads on how to build one. If you're serious about doing your own repairs you won't want to be without one.
    gort69 likes this.
  3. rickl

    rickl Active Member

    Twin Cities
    I like your enthusiasm for learning.
    Along with hopjohn's suggestion to build a DBT, I'd suggest searching this forum for 7070. I found a few common problems that may help guide you too. I've had great success fixing stuff by reading what others have done. hifiengine has the schematic. while it nice to be able to read a schematic, being able to count pins on a board can be useful for measuring voltages. download the schematic and start reviewing it.

    Also state your location. Someone close may offer to help you.

    DBT, DMM, and the TLA for a soldering iron will go far.

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