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Power Supply

by glchandler
7 replies
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I am cobbing a computer together from spare parts...the motherboard I am using is a server board specifying will not boot without minimum of 5v supplied.

I measure between 4.5v and 4.8 volts on the power connectors, including the cpu power cable. This is a 600W psu with stated output of 5v for 42amps.

Is this variance enough to keep the motherboard from firing? If so how can I increase this voltage or where else can I look for a bit more volts??
  • Profile picture of the author Mike Wright
    Have you actually tried powering up the mobo and seeing if it boots ?????
    PSU voltages are fixed and dependant upon production tolerances.

    Unless you are trying to cobble a server together, you may well be far
    better off making a standard PC imho :0)
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    • Profile picture of the author glchandler
      Have the whole thing assembled.....onboard fans work...cooling tunnels on cpu's work and the dvd I put in opens and spins.
      However no video output or anything else with mobo...disconnect and check voltage is when I get the readings under 5v. mobo stats calls for minimum of 5 to boot.

      And, yep I understand I would be better off going the other way but this is a challenge to pull a bunch out of a pile and make a box work! Hate to give up when I might just be 00.015 Volts away from success!!!
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      • Profile picture of the author glchandler
        Understand that very few here might have an answer but maybe a suggestion to a good techie forum they won't laugh me off of??

        thanks
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  • Profile picture of the author westom
    Originally Posted by glchandler View Post

    I measure between 4.5v and 4.8 volts on the power connectors, including the cpu power cable. This is a 600W psu with stated output of 5v for 42amps.
    If the supply can provide 5 volts, then it provides 5 volts. However, where are your two probes making that measurement? On a red and a black wire from power supply?

    If 5 volts is below 4.87, then the supply is defective (in that system) for any one of a long list of reasons. Including good supply defective with that load. Motherboard needs more than 42 amps. Electrolytic capacitors defective but not yet visibly apparent. Or maybe 15 other reasons.

    Ignore power supply wattage. That is what the technically naive hype - dollars and watts. Your only important numbers are current for each voltage. Only way to identify a good or bad system are voltages from each critical supply - any one of red, orange, yellow, and purple wires.

    For some unknown reason, that supply is defective in that location. With a meter, you could learn more. A defective supply can even boot a computer. The naive will claim that supply as good. Your tests show that supply is defective in that system no matter what the computer does.
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    • Profile picture of the author glchandler
      Don't wish to be less then appreciative for any answers but my question was meant only to be in regard to the amount of variance acceptable on the psu output.

      Almost any source of voltage varies from time to time....DC varies less and more infrequent than AC.

      Of course the amperage available to any portion of the computer is the determining factor however the wattage of the psu is not necessarily hype....if I recall any of Ohms law then you cannot seek higher current with the same voltage input unless you increase the wattage.
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  • Profile picture of the author webpromotions
    You need to ask this question at the forum on tomshardware.com.

    You definitely don't want to ignore PS wattage - you just need to ignore the specified watts if its a cheap power supply, as they are very often overstated.

    Maybe things have changed since years ago when I was into the 'build your own pc' thing, but back then, the power supply was the key. Back then, it was 'spend a good 200-300 on a top of the line Antec, then build the rest around it'.
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    • Profile picture of the author glchandler
      Thanks for the link.....oft times the "good old days" when you could adjust or rebuild things such as power supplies and voltage regulators are missed!
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      There is never a BAD time to help those living with lousy kidneys!
      http://funds.gofundme.com/1oh40


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