Amp Malfunction

Discussion in 'Amps and Cabs [BG]' started by Thrilldg, Nov 29, 2005.

  1. Hey all,
    I posted this is in a possibly worng forum and was directed here. So, without further ado,
    I have a Fender BXR200 combo that I purchased used about two years ago. Last night at a practice my amp decided to start humming. Humming might not be appropriate, it was more like a fire alarm noise. Needless to say, the gist is that it started to make only one tone at the same volume level no matter what the master was set on (when all was set to zero; master, eq, etc, the tone persisted). No actual bass sound (from my playing) would come out... you get the idea I'm sure. My question is, is the is fixable problem, and if so is it worth it to try to get it repaired?
  2. Does your amp do this without anything plugged into the input? (without the bass and instrument cable or any effects plugged in)
  3. Yeah, it makes the noise regardless of volume levels or inputs. With nothing on and nothing plugged in, just the amp in the wall the noise is made.
  4. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Here is my hypothesis: Loose connection in the power supply, resulting in partially or completely unfiltered AC going to the power amp circuit. Also possibly a broken ground connection somewhere in the chassis.

    If the amp has a switch for turning off the internal speaker, you can do so, and then attach a voltmeter to the extension speaker jack. Any DC voltage above a few tenths of a volt indicates that the power supply or the power amp circuit itself are at fault. Don't do this unless you know how to do it safely.

    Unfortunately, messing with the high power portions of an amp can get you hurt, and can also cause additional damage if you make a mistake. This is probably a job for a tech.

    In addition, if there is something unbalanced in the power amp, it could be progressively damaging the speaker. Another reason to get it to a tech.
  5. tadawson


    Aug 24, 2005
    Lewisville, TX
    Well, comments from the electronics point of view:

    Is is fixable? --> Frankly, there is nothing that is not - this is a kinda dumb question. The better question would be "Can this be fixed for a price that I can live with", and that I can't tell you. Typically, stuff like this is pretty simple - no smoke has leaked out, after all . . . . .

    It would help also to get a better idea of the sound. If it is a loud hum, then the grounding/power supply comments posted so far make some sense. If it is a higher pitch, then something in the amp either failed or came loose, and it is oscillating. In either case, it sounds like a cheap problem to fix.

    - Tim
  6. Thanks for the posts. I suspect that the power supply hypothesis is more likely correct, as the tone is a constant not high pitched (not low either) one from the onset of starting to run any power through the amp. If anyone has any suggestions of places in Atlanta that can do this work I am all ears (I live in Athens and I cannot find anyone who does solid state repairs for bass amps).
  7. tadawson


    Aug 24, 2005
    Lewisville, TX