Need help diagnosing amplifier problem

Discussion in 'The Projects Forum' started by SilvrEclipse, Feb 27, 2010.

  1. SilvrEclipse

    Thread Starter Active Member

    Nov 21, 2007
    The amp is an Audiobahn A8002T amp, class AB, 2 channel.

    The amp was running bridged and was overheated several times. Now the right channel does not work at all. The left channel still works perfect and there are no other problems other than the right channel not working.

    I have taken the amp apart and checked it for obvious damage. Didn't see any burn marks on the board, resisters look find, caps look fine. I checked the mosfets real quick with a multimeter just making sure none of them were shorted. They all seemed fine.

    Some of the mosfets on the power side of the board do look like they have been exposed to lots of heat. The silver on the back side is dull looking and has some texture to it. I checked the voltages on the mosfets with the amp on and 1 did have different values than the other ones but it would seem like all of these would have to be blown for the channel to not work at all. Also it was on the opposite side of the board than the blown channel.

    Any guidence on some things I can check for? It has to be something simple that I am missing.

    Thanks guys
  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    The fact that one of the channels is still working gives you a major advantage in troubleshooting the failed channel.

    If you have access to an oscilloscope, locating the failed channel should be fairly straightfoward. The task is somewhat more of a challenge if all you have is a digital multimeter.

    Do you have or can you obtain a schematic?

  3. SilvrEclipse

    Thread Starter Active Member

    Nov 21, 2007
    I have no been able to track down a schematic yet but still working on it. Yea it should be fairly easy to figure out since I have the other channel to compare it to. Dont have access to an o-scope unfortunately.

    Im kind of lost on where to go from here, it doesn't seem like an output transister failed since those usually short out and throw the amp into protect mode. I guess when I get some more time I will have to go threw the whole board and hope i find the problem.