Why Does A Circuit Stop Working

Discussion in 'The Projects Forum' started by djsfantasi, Sep 23, 2010.

  1. djsfantasi

    Thread Starter AAC Fanatic!

    Apr 11, 2010
    I had a circuit developed and tested successfully. The circuit board actually had two circuits - an audio amplifier and an audio envelope follower - on it.
    The audio envelope follower stopped working.
    I did mount it in an enclosure.
    The amplifier still works - so doubt if its a power problem.
    Visual inspection of the board does not show any bad solder joints nor broken traces. It was a commercially prepared board (hence I don't think its a bad trace problem.)
    Everything except the basic circuit has been disconnected, to eliminate any related issues.
    What else can I do to check it out? Check resistors/trim pots with my meter... (in circuit?)... Check diode for function (in circuit?)... Replace Op Amp...
    Any other ideas? (The circuit in question is attached)
  2. kubeek


    Sep 20, 2005
    Use oscilloscope and track the signal along the path, that should lead you to the problem.
    djsfantasi likes this.
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    Check the capacitors.
    djsfantasi likes this.
  4. Ghar

    Active Member

    Mar 8, 2010
    Is the enclosure metal and is it touching anything?
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  5. djsfantasi

    Thread Starter AAC Fanatic!

    Apr 11, 2010
    No oscilliscope... How do you check caps in circuit? The enclosure was non-conductive, fasteners were metal but the board design kept them isolated.

    However, it helps when you are processing an audio signal that its volume is high enough to be detected by the circuit as designed... My bad - I found out that my media player had its volume setting turned way down. Basically, I paniced because I felt that I didn;t have the tools nor experience to debug the problem. Thanks all for your suggestions!
  6. Wendy


    Mar 24, 2008
    Welcome to the world of troubleshooting. A DVM is the first place you start, you should know what voltages you should see where in your circuit. Using the voltage meter look for wrong voltages. This will give you an area to focus on.
  7. tom66

    Senior Member

    May 9, 2009
    I have made this mistake far too many times with regards to plugging the video input into the wrong pin (for a project) and wondering why it wasn't working. Unfortunately your mind starts jumping to conclusions like "the breadboard must be faulty" or "the chip is damaged", not "a wire is loose." :rolleyes: