Low and distorted output out of my Peavey KB60

Discussion in 'Amps and Cabs [BG]' started by dindinbre, Sep 14, 2017.


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  1. dindinbre

    dindinbre

    Aug 2, 2017
    Serbia
    Hello! I have bought this monster several months ago and it played GREAT for keyboard amp, had big tone, no buzz, and was overall in good condition. I have played bass and music through it since first day, much better than PC speakers i own. Yesterday I started it up, LED blinked and turned off. Ok, i knew it was blown fuse, went to electro shop, bought another one, swapped it and it turned on. Then i have connected speaker aaand... Very low (phone loudspeaker at 1/4 volume is louder than amp right now) and heavily distorted sound. I know it isn't speaker, tried out headphone out and i got same, heavily distorted low sound. Every input, power amp in, same thing goes on. What could it be? Inspected it inside by eye and everything seems fine, no blown capacitor or whatsoever. I will try to upload pictures tomorrow...
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Could be (and most likely is) a major circuit failure. Technician time unless you have test equipment and understand how audio power amp circuits work.
     
    dindinbre likes this.
  3. dindinbre

    dindinbre

    Aug 2, 2017
    Serbia
    That is bad :( If it was transistor or capacitor I could have changed it in minutes... Eh, seems like money i saved for effects will go on fixing.
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Sure, if you know what part, it's easy... but which one? All the expense is in correctly determining which parts have failed, and rarely is it a single part, and most parts do not show physical damage.
     
  5. dindinbre

    dindinbre

    Aug 2, 2017
    Serbia
    I have a multimeter, tested out most resistors and they were ok. One concrete resistor looks like falling apart and that's it i guess. Sadly its just basic instrument with Ohmmeter, Voltmeter and Ampermeter. I know basic electronics and how amplifiers work, but seems like i cant fix this myself...
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    You will need to understand feedback amplifier theory and operation because the feedback affects every measurement that you would make. (ie. you expect a positive voltage but the voltage is in fact negative, but the negative voltage may be from a fault on the positive half, etc.) If you don't understand, nothing will make sense.
     
  7. Did you put in the exact same type of fuse?
    If you put in one with a slower "blow" time or higher current, you may have made things worse.
    Though it does sound like bench time anyway.
    Good luck - Hope you get her going soon.
     
  8. dindinbre

    dindinbre

    Aug 2, 2017
    Serbia
    Yes, i did put the same 1A fuse. That is my only amp, now i need to play acoustically again, that sucks :/
     
  9. dindinbre

    dindinbre

    Aug 2, 2017
    Serbia
    Well it took me a bit to find technician who works with instrument equipment... From his words amp got electrocuted with high voltage input! It burned entire output circuit. Repair costed me 17 (7 for parts and 10 for his work) dollars! Well I am glad sometimes that i live in Eastern Europe.
     
    BassmanPaul and agedhorse like this.
  10. Glad it was a cheap fix for ya
     
    dindinbre likes this.
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