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Radio Shack power supply

Discussion in 'Troubleshooting and Repair' started by tj107us, Sep 3, 2012.

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  1. tj107us


    Apr 23, 2011
    Hey guys I'm working on another project, its a 13.8vdc power supply that has quit working and i need to know how to test a voltage regulator Item # LAS1905B. I have attached a photo of it.

    thanks for any help,

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010

    Measure the input voltage and the output voltage. If the input voltage is more than a couple of volts higher that the regulator's specified output, the output should be within a couple of percent of the rated output voltage.

    It should stay that way under load until either the internal current limit is reached, it overheats, or the input voltage sags.

    The above text is generic. You will need to read the datasheet for more specific information.
  3. tj107us


    Apr 23, 2011
    how would i check the voltage, ive tried looking it up but all i can find is how to test a auto/motorcycle type voltage regulator?
  4. john monks

    john monks

    Mar 9, 2012
    Let me take a crack at it. Place anywhere from about 8 volts to 30 volts between pin 1 and the case. Pin 1 should be positive. Take a voltmeter and place it between pin 2 and the case. You should read about 5 volts.
  5. tj107us


    Apr 23, 2011
    ok thanks John and Steve!!!
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