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Painfully loud hum: Yorkville XM100C

Discussion in 'Amps and Cabs [BG]' started by zillo, Nov 6, 2005.

  1. zillo


    Jun 5, 2003
    :( Hi:

    I plugged the bass in this morning, turned on the combo, played a couple of notes, and then heard a pop.

    A loud humming sound commenced, and the speaker was vibrating and "extended"...that is the speaker was pushed outward.

    I checked the passive and active inputs; same result. Plugged into a head with the same cable, no problem.

    Anybody have any idea about what might have just happened?

  2. i'm not sure if i could relate, but I've been known to have instances where I turn on my amp, get a painfully high feedback pitched noise, banged it a few times, and eventually played through it until it vibrated the head back to where it wouldn't have a problem...now while i sound like an IDIOT, i did discover something in my old Peavey combo after my shop guy took a look. sometimes it has to do with the cables in between teh connection between the head and the speaker cab oxidizing. that or maybe from a bit of rough transportation it bumped out? no clue, but this has been my experience with a combo amp
  3. I'm no expert on amp design but sounds to me like the DC-bias cap has popped, if there's such a thing in that amp. A really easy way to tell if a cap has blown is to measure resistance across it. A good cap should initially show a short circuit, but then quickly show an open. A blown cap will show a short, and stay that way, OR show an open and stay that way. Unless of course there are other caps in parallel, in which case its a royal PITA to find. In the case of a shorted cap, you need to remove it from the circuit and test again to be sure its the culprit. There could be other caps in parallel that have shorted, so when you pull the culprit, it may measure ok out of the circuit. Anyway...

    I can't personally recommend playing with caps, especially big ones. Take it to a Yorkville dealer and explain it to them... Yorkie has one of the best warranties in the bus!

    - Andrew
  4. zillo


    Jun 5, 2003
    Hey..many thanks.

    I took the head out, and everything is still wired up.

    I'll take it to the dealer and hope for the best.