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Thread: PSU problems?

  1. #1
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    PSU problems?

    hello,

    In my "new" build, I'm actually using a (almost) 3 year old Tagan 380W PSU.

    At the back, like a lot of PSU's, I have an on/off switch. The problem I have is, when I switch this off, and then back on again, the system fails to start. Sometimes it will switch on for a second, and then turn back off. To get it working again, I have to flip the switch several times rapidly, and then the system will work fine when I turn it on. Strangely, turning off the PSU at the mains has no effect. Ie if I turn the system off at the mains, then switch it back on, I have no problems. It's only when I flip the switch on the actual PSU.

    I'm not sure, but it seems more like a mechanical problem rather than a major fault with the PSU (maybe something loose in the switch asssembly?). I have minimal knowledge on PSU's though.

    I've made sure the grounding wire from the PSU is secured to the case, and I am using an earthed 3-pin power cable.

    Any ideas?
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    Re: PSU problems?

    Tagans must have a 3 year warranty, try and get it repaired / replaced.

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    Re: PSU problems?

    Sounds like 1 or more capacitors are high ESR. The repeated cycling OFF/ON will heat them up and in so doing, reduce their ESR to a point where the PSU can start up.
    It will get progressively worse untill it either it blows the external or internal fuse.
    I`d suggest giving it to the bin, unless you know someone with a soldering iron.
    And unlike the chap in the Scan forum, don`t keep throwing new fuses at it !

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    Re: PSU problems?

    Quote Originally Posted by Blenster View Post
    Sounds like 1 or more capacitors are high ESR. The repeated cycling OFF/ON will heat them up and in so doing, reduce their ESR to a point where the PSU can start up.
    It will get progressively worse untill it either it blows the external or internal fuse.
    I`d suggest giving it to the bin, unless you know someone with a soldering iron.
    And unlike the chap in the Scan forum, don`t keep throwing new fuses at it !
    Interesting diagnosis...

    I can't see how a high ESR at any point in a PSU would affect the soft starting capability or how changing temperature would affect the ESR. There may well be a faulty capacitor in or around the inverter cicuitry, but I don't believe it would be ESR related. ESR is really only significant in RF circuits.

    Please can you explain where in a SMPS high ESR would be signifcant and how ESR is related to temperature ?
    Last edited by peterb; 02-11-2008 at 08:59 PM.
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    Re: PSU problems?

    Buggered PSU. The capacitors in my 4-year-old Tagan 420w were completely knackered - some were bulging, one medium-sized cap had one leg transformed into a mini mountain of iron oxide. The only signs I had of a PSU failure were....

    1) intermittent startup BSODs (but I only powered it off+on maybe once every 4 months)
    2) dead hard drive
    3) the most obvious, transferring it to my Dell GX280 yielded the "bad psu" status LED and it refusing to power up

    If you reckon you won't accidentally touch any bare metal, take the cover off (it's very easy) and peek at the capacitors.

    Otherwise, measure the voltages with a multimeter.

    edit: don't think about doing a DIY job on the caps inside - it's impossible to get to them, as the heatsinks are both soldered and screwed to the PCB, and the screws attaching to the voltage regulators to the caps are impossible to reach.
    Last edited by smargh; 02-11-2008 at 09:12 PM.

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    Re: PSU problems?

    If it switches on fine from the wall socket you'd really have to take a punt at the switch being faulty. Ive seen this on a few supplies where the switch gives out after some use.

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    Re: PSU problems?

    When Tagan's first appeared on the market, I was impressed by their build quality. However, I've just had a pair of just-out-of-warranty Tagan's fail on me...

    You should use the opportunity to invest in a new, more efficient PSU.

    On my dual dual-core Opteron system, the old Tagan sucked 210W on idle. According to my same power meter, the identical hardware powered with a new 80%+ efficient Corsair TX650W, my idle consumption has dropped down to about 155W.

    And I even plugged in an identical Tagan to the failed one, just to make sure that wasn't a fault with the original PSU for the high consumption....

    So, with the new PSU, I'm saving almost a third of the energy... I'm now tempted to replace all my old Tagan's with newer, more efficient PSU's, on at least my systems running 24*7...

    I've also had some success with Antex Earthwayys PSU's - more basic that the Corsair, but cheaper....

    Russell

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