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New Amp blow fuse now there’s a buzz and a crackle!

Discussion in 'Amps and Cabs [BG]' started by basscolon, Oct 19, 2018.


  1. basscolon

    basscolon

    Oct 18, 2018
    Lubbock, TX
    Hi everyone, we evenly acquired some used gear a bass guitar (Warwick) and bass amp (orange ad200B with 810 cab). While trying to set up the bass we had an issue in which the audio jack in the bass where the cable goes in wasn’t being held in properly and popped out. This led to an uncomfortable popping sound from the amp then whenever we tried to play a note no sound would come out but a fuzzy grrring noise and upon further inspection we found two blown fuses. We change them out, and the head not turns on and plays, but there is an awful buzzing and crackling, it gets worse if we turn the gain up. We fear it may be something really worse than just power tubes, but we are also hoping it is just power tubes. We have no amp techs nearby... so we are at a loss.
     
  2. Bim1959

    Bim1959

    Apr 15, 2009
    Naples Florida
    Sales and electronic tech/piano tech: England Music Center - Clinton IA - now closed
    Welcome to Talkbass!!!!

    If you could fill out your profile it would help us to tell you where to send your bass and amp off for repairs if you havent worked on anything like this before.

    A few questions first though.

    Are you using the proper cable to hook the cabinet up to the amp? It needs to be an actual speaker cord and not an instrument cable as those will hurt an amp.

    Have you tried using another bass or guitar and a different instrument cable to run between the instrument and the amp? The cord you were using might have a problem also.

    Also. Unless you have the knowledge to repair that amp I wouldnt open it up and randomly replace fuses or other components. Those fuses were blown because there is a problem in the amp that will possibly become worse now that another fuse was installed.

    If you dont have anything else to check out the amp with you really need to send the amp and the bass off to be repaired.

    Good luck!!
     
  3. basscolon

    basscolon

    Oct 18, 2018
    Lubbock, TX
    Thank you for the response. I have done the following, tried different cable, different cab and different guitar yet problem still persist. I replaced one of the HT fuses and one of the output valve failure fuses. The amp will turn on, plays well, sounds good... except for a buzz that increases with the increase of either the master volume or gain. But completely vanishes when both are at zero. Everything sounds as it did before the buzz and a periodic staticky sound. I have changed tubes and rebiased plenty of amps before. And know my way around with a multimeter. I suspect it may be a power tube, and I’m hoping nothing more... the amp has been great for the past two days that I’ve owned it. Until today when the guitar cable came out of the loose input jack on my Warwick thumb. After a pop there was still sound but only a low volume fuzzy sound, when I played a note. After replacing the fuses the volume and controls went back to normal, with the added hum and static. Visual inspection shows all the wires, caps, and resistors looking as good as new. Worked on many guitar amps in my life just wouldn’t consider myself a professional. I just wanted to throw this out to see what opinions everyone else may have. I ordered all new tubes, and a bias probe, I will install them and bias them between 18-22mA (I believe those are the correct values) and will fire her up, if it persist then I will look into sending it off for repair. Thank you again!
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    You will want to current limit the supply input to your amp and monitor the plate currents otherwise you run the risk of ruining a set of new tubes and causing more damage to your amp in the process.

    Do you have a scope? Do you know how to measure current sharing of an output stage?
     

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