Anyone ever see a bad power supply still show voltage on a meter?

nspindel
nspindel Posts: 5,343
edited December 2013 in The Clubhouse
I run SageTV in my house, which is a DVR that runs on your computer with external tuners that record to the computer's hard drive. I have one tuner from Hauppauge called an HD-PVR, which all of a sudden stopped functioning. The power light was on, but it was no longer being recognized by Windows. I read on the SageTV forums that this problem could be caused by the 5v cheapie power supply going bad. I tested the power supply with my volt meter, and it read a rock-steady 5.18v. But after trying several other possible fixes, I finally swapped in the power supply from my Squeezebox, which is also 5v, and sure enough that fixed the problem. It's definitely the power supply, if I swap them back and forth the problem comes and goes. But yet the bad power supply still reads correct voltage on my meter. Anyone ever see something like this before?
Good music, a good source, and good power can make SDA's sing. Tubes make them dance.
Post edited by nspindel on
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Comments

  • maximillian
    maximillian Posts: 2,144
    edited December 2013
    Are you testing the power supply under load or simply measuring the connector unplugged? It could be providing very little current. Also, PS's can also start producing lots of noise on the output that could be **** things up.
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  • nspindel
    nspindel Posts: 5,343
    edited December 2013
    I am just measuring the unplugged connector. How would I do it otherwise?
    Good music, a good source, and good power can make SDA's sing. Tubes make them dance.
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  • billbillw
    billbillw Posts: 6,867
    edited December 2013
    A regular mulit-meter doesn't show ripple and/or other inconsistencies with a power supply.
    For rig details, see my profile. Nothing here anymore...
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  • nspindel
    nspindel Posts: 5,343
    edited December 2013
    Ok. I thought if the power supply goes bad, it just dies. Didn't realize it was more complicated. Thanks for the advice.
    Good music, a good source, and good power can make SDA's sing. Tubes make them dance.
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  • SCompRacer
    SCompRacer Posts: 8,513
    edited December 2013
    nspindel wrote: »
    I am just measuring the unplugged connector. How would I do it otherwise?

    Depends on type of power supply. But connected to load is best test. You might see voltage fall with it loaded as it can't supply the mA or amps required to power/run the device.
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  • sucks2beme
    sucks2beme Posts: 5,606
    edited December 2013
    5vdc might be 5 vdc. Or have a heavy ripple. Or drop under load to way lower than 5 vdc.
    A quick meter check is just that. 1st step in many. Getting meter leads on hot circuits is hard,
    but a must when testing.
    In testing ac power, I have a wiggy (a type of tester) that draws a load.
    unlike a meter, it will tell you if you have any current behind the voltage.
    Same for automotive testing, good battery testing involves putting a load on the battery.
    "The legitimate powers of government extend to such acts only as are injurious to others. But it does me no injury for my neighbour to say there are twenty gods, or no god. It neither picks my pocket nor breaks my leg." --Thomas Jefferson
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