Restore Mickey Mouse!

Discussion in 'General Electronics Chat' started by johndoe45, Jun 24, 2011.

  1. johndoe45

    Thread Starter Member

    Jan 30, 2010
    My girlfriend has a talking mickey mouse that she wants me to try and fix.

    So here are the circuit boards. The voltage isn't making it to all of the connectors. but I am getting the 6 something volts from 4 C batteries from the connector and on the beginning of the board.

    Any help would be appreciated. Like where to test for voltage points.
    I have a copper wire soldered to ground of input connector as in bottom picture so i can alligator clip my DMM to it.
  2. hgmjr


    Jan 28, 2005
    The presence of the bare copper wire so close to other connections has me concerned. If you have some insulating electrical tape it would be a good idea to put a small piece on the area of the board beneath the wire to avoid the possibility of a short between the bare wire and one of the exposed connections on the board.

  3. KJ6EAD

    Senior Member

    Apr 30, 2011
    The first step would be careful visual inspection. Look for cold solder joints or cracks in the solder around component leads. Pay special attention to areas of the board that are subjected to mechanical stress such as the connector headers, near mounting holes and any thin sections such as that finger of board in the corner and around any large or heavy components. This board was wave soldered so the header pins are a likely spot for cold joints. Flux and reflow anything that looks questionable.
    Last edited: Jun 24, 2011
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010


    Looks suspicious to my eye, but pictures are hard to use for solder joint exams.
    check that closely. Also consider changing out the large cap near the power pins, just for good measure. As stated by others, the problem will probably be due to solder breaks or shorts from long handling of the item.
  5. johndoe45

    Thread Starter Member

    Jan 30, 2010
    i have resoldered a lot of joints.

    Is an 4-7 esr high for a 3.3 uF capacitor?

    Because on the chart for the Blue ESR I think it says 10+ is bad

    the silver thing circled above. is it a capacitor? has no label. i fixed the wire on circled one two posts before but it is connected by a trace anyway.
  6. tom66

    Senior Member

    May 9, 2009
    Looks like a crystal oscillator, if that is shorted to a pin then it will not oscillate so there will be no sound.
  7. johndoe45

    Thread Starter Member

    Jan 30, 2010
    ok here is what i got so far. replaced some caps. resoldered some joints.

    also, the red is a pnp transistor.

    the number on it says

    O :. 7G

    the black pin is 0 volts. so i think this component is bad because the Low Voltage Audio Power Amplifier LM386-1 is not getting the supply voltage (circled in white). Yellow is trace from the 0 volts to Vs of amplifier.

    EDIT: However. I just removed it. Tested it with analog ohmeter. From base to emitter. one reading. Base to collector one reading. collector to emitter no reading. So it is fine. So what else could cause no voltage to the amplifier Vs???
    Last edited: Jun 28, 2011
  8. johndoe45

    Thread Starter Member

    Jan 30, 2010
    here is a better picture of the circuit board.
    • new.jpg
      File size:
      338.4 KB
  9. johndoe45

    Thread Starter Member

    Jan 30, 2010
    that pnp transistor i said before still tests out fine with the analog meter.

    i lifted the leg out that was measuring 0 volts to separate it from the circuit and it was still 0 volts. :confused:

    so is this a problem?
    Last edited: Jul 11, 2011