LM386 - failure mode?

Discussion in 'General Electronics Chat' started by Mike33, Jun 7, 2010.

  1. Mike33

    Thread Starter AAC Fanatic!

    Feb 4, 2005
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    Hi, I am wondering if anyone knows enough about the LM386 to tell me {what I already suspect} if it's dead. I am getting continuity between pins 3 and 4, with no solder bridges or other 'user' issues. I have signal between pins 1 and 8 (I do have the 10uF gain cap there), but nothing at output.

    That is continuity between the + input and ground, so I am thinking I am going to have to rip the puppy out of there and replace it. :SIGH: the 1 time I didn't have an IC socket!! And the circuit it a bit large, so this has been busting me on debugging.
    Thanks!

    ~Mike
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    If you get substantially different readings from 3 to ground as you get from 2 to ground, try un-soldering parts that are connecting those pins elsewhere. If you still are getting a short from 3 to ground, replace it.
     
  3. Mike33

    Thread Starter AAC Fanatic!

    Feb 4, 2005
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    Thanks, Sgt. I think I'll take it out and put a socket in there, while I'm dickering with it.

    What would cause an 'issue' if unsoldering the coupling parts actually works?? I've had that happen, have switched from the "+" input to the "-" and had the amplifier work. Never understood why. It's just a coupling cap, no pulldown resistor or anything.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    You have to follow the example schematics in the datasheet. If you swap the inputs from what's shown, it won't work.
     
  5. Mike33

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    Feb 4, 2005
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    I guess I learned that one the hard way, he he. Works now, thank you :eek:) Another lesson on "use an IC socket"!!
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    No.
    The inputs are a true differential, both are biased at ground and the negative feedback is internal.
    The LM386 works perfectly with either input pin as the input and is shown both ways on the datasheet.
     
  7. Mike33

    Thread Starter AAC Fanatic!

    Feb 4, 2005
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    Which is odd, Audio, since I have had circuits behave differently based on which input I chose (no phasing or stereo issues, just a basic amplifier application). Very strange.
     
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