Failure of the Marshall MG15R

Discussion in 'The Workbench' started by enaMi, Jan 27, 2021.

  1. enaMi

    enaMi New Member

    Joined:
    Jan 27, 2021
    Messages:
    2
    Likes Received:
    0
    Hello. What could be the reason for the failure of the Marshall MG15R (2011) guitar amplifier and can I fix it myself (I do not have any experience). Below I will try to describe the states of the amplifier's behavior. 1 / After switching on, the LED in the Channel button is off (currently it is not lit at all, and the button being pressed does not work) and a rhythmic knock is heard from the speaker. If I do not turn anything, after few seconds a short noise is heard and the knock disappears. Turning it on again does not help, there is no sound coming from the speaker. The knock returns when I connect the amplifier after some time, e.g. on the next day. 2 / When I start turning the control after switching on, the knock from the speaker does not disappear. In addition, if I turn the Clean Volume control, the knock becomes louder and faster (towards 10). It also gets faster if I turn the Reverb control towards 10, and it becomes slower when I go back to 0. Turning the Bass and Treble controls causes two states: in one direction, the knock as you turn the control in one direction disappears, and in the other it speeds up. Other potentiometers do not respond. 3 / If I turn on the amplifier and with the Power button turned on, I remove the plug from the socket and turn it on again, the volume and knock frequency are already regulated by Overdrive Volume. It doesn't always happen, but it does. In general, the breakdown began with the fact that I plugged the plug into the socket with the Power button turned on. 4 / In the loudspeaker you cannot hear the guitar connected, only when you hit the bass strings hard you can hear a short response in the loudspeaker, I would describe it as distorted, dirty distortion. But in general, the guitar cannot be heard at all. 5 / The connected MP3 works fine, music is heard through the speaker with a clicking sound. Similarly with headphones, you can hear mp3 music in the headphones. I would like to add that after plugging in the headphones, the knock goes to them, the speaker goes silent.
    Can you advise something? Can I fix it myself without specialized equipment? Please help. Thank you.
    Sorry for my English but I was assisting with google translator.
     
  2. Matthews Guitars

    Matthews Guitars Well-Known Member

    Joined:
    Aug 17, 2019
    Messages:
    3,127
    Likes Received:
    4,697
    I doubt you can fix this yourself. This requires an electronic technician with good troubleshooting skills.
     
    KraftyBob and Old Punker like this.
  3. Max Gahne

    Max Gahne Active Member

    Joined:
    Dec 1, 2020
    Messages:
    112
    Likes Received:
    130
    It doesn't sound like it's something you can fix. It's 10 years old. I'm in the US and I see here a new MG15R maps for 140$ US shop labor rates are around 70$/hour I think and it sounds like your amp has at least 2 hours of shop time in it. I think it's time for a new amp.
     
    trax1139, KraftyBob and Old Punker like this.
  4. Old Punker

    Old Punker Well-Known Member

    Joined:
    Jun 17, 2020
    Messages:
    600
    Likes Received:
    1,454
    Location:
    Ontario, Canada
    :welcome: to the forum. Unfortunately it sounds like your amp has serious issues, maybe a bad circuit board? If you are not experienced in repairing electronics then I would agree with @Max Gahne, time for a new amp.
     
    KraftyBob likes this.
  5. KraftyBob

    KraftyBob Well-Known Member Gold Supporting Member

    Joined:
    Sep 5, 2017
    Messages:
    1,843
    Likes Received:
    2,362
    Location:
    Chicago Suburbs - USA
    Based on your description it sounds like you may have a ground issue, among other things. I say this because the low level/distorted guitar signal sounds similar to an amp I repaired that had a ground issue. This happened to be with a cathode resistor in a tube amp - but still, it was a ground issue. There could be other reasons, but I figured I'd mention it.

    I would venture to guess the reason why the knocking comes and goes is because of the filter capacitors in your amp. I don't think they are the issue, rather it's the nature of how these work. The filter caps store high voltage and charge up when the amp is powered on. When the amp is powered off there is still a lot of voltage remaining in them, and if you turn it back on right away they are at, or close to full charge so you don't hear the knock. However, when you plug it in again on day 2 the caps have likely drained enough over night that they need to recharge and the knock returns.

    Having said all this, I agree with the others in that this is not something someone with no experience can likely fix. Also, while solid state amps don't carry as much voltage as tube amps, you can still get a nice jolt if you touch the wrong spot.

    You got 10 years out of this one. Sorry to say but it's time for a new amp.
     
    Old Punker likes this.
  6. enaMi

    enaMi New Member

    Joined:
    Jan 27, 2021
    Messages:
    2
    Likes Received:
    0
    Thank you for all the answers.
     

Share This Page