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Thread: Weird fault on OCZ StealthXStream 400W

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    Default Weird fault on OCZ StealthXStream 400W

    I'm looking for some assistance diagnosing and fixing an OCZ StealthXStream 400W PSU.

    It has a weird fault in that it will power up my Gigabyte MA780G-UD3H/Phenom II X4 720/8GB DDR2 system but with my Biostar TA790GXBE/Athlon II X4 630/8GB DDR3 or Asrock 880GMH board with same components, the PSU and CPU fans spin up but then the PSU shuts down after a couple of seconds. All boards were using onboard graphics and no addon cards. The CPU and RAM have been tested OK on other boards.

    I've checked inside and there's no bulging/leaking caps or other obviously damaged components so I'm not sure what to test. I've got a digital meter if anyone could advise where to start.

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    Do you have one of those handheld PSU testers with the LCD display that can tell you what the power good signal is?

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    Quote Originally Posted by jonnyGURU View Post
    Do you have one of those handheld PSU testers with the LCD display that can tell you what the power good signal is?
    Unfortunately not, I'd have to just test each line individually with my meter.

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    No. There's a power good signal on the PSU. It's a timed signal that's measured in milliseconds. The #1 reason for a PSU to work on one motherboard but not another is if the timing of the power good signal is not what the motherboard is expecting. Essentially, the motherboard wants to know if all of the voltages are where they need to be within a certain period of time. If the PSU can't report that it is ready within a certain period of time, the motherboard shuts down.

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    Does this happen often? Anyone?

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    Quote Originally Posted by jonnyGURU View Post
    No. There's a power good signal on the PSU. It's a timed signal that's measured in milliseconds. The #1 reason for a PSU to work on one motherboard but not another is if the timing of the power good signal is not what the motherboard is expecting. Essentially, the motherboard wants to know if all of the voltages are where they need to be within a certain period of time. If the PSU can't report that it is ready within a certain period of time, the motherboard shuts down.
    Ah gotcha. I should have given more background in my post but was trying to keep it brief and not post a lot of irrelevant stuff about the history. Anyway, I should mention that the OCZ did work fine on the Biostar board for about 9 months before it suddenly developed this problem. The fan started making nasty noises first, so I RMA'd it but they couldn't hear the problem and when I got it back it had stopped doing it and was OK for a couple of months before it started again. It cost me about £25 to send it there and back, so I replaced the fan myself with a £12 NoiseBlocker BlackSilent Pro PK2 rather than go through that again and it was fine for a month or two before this problem started.

    I can certainly check whether the Power Good line is sending the 5v as it should, although measuring the timing down to the millisecond is going to be impossible. I guess if it's not sending it properly, that could mean there's a problem with one of the voltages or just with the Power Good circuit.

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    I've seen ODM's do something as simple as swap out a resistor (Topower when making BFG's GS650) and see the power good signal change. If that same resistor were to fail, you could have the same symptom.

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    If you have access to a microcontroller (Arduino, MSP430, etc) it's very simple to make your own power good delay tester.

    To get a good read on it you'll either need a digital scope, a microcontroller, or one of those handheld jobbies.

    I think it could be done with discreet components, a 555 and some resistors and a capacitor, but it'd be tricky.

    If I remember correctly the proper range is 200-500ms. You could almost use a stopwatch and an LED on the line (with resistor, of course, and going to ground rather than in-line) to take a reading on it. The accuracy would not be good, but it ought to be enough to tell you whether it's in the right ballpark.

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    Quote Originally Posted by jonnyGURU View Post
    I've seen ODM's do something as simple as swap out a resistor (Topower when making BFG's GS650) and see the power good signal change. If that same resistor were to fail, you could have the same symptom.
    OK, guess it's worth checking the resistors for that circuit then.

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    Quote Originally Posted by bobnova View Post
    If you have access to a microcontroller (Arduino, MSP430, etc) it's very simple to make your own power good delay tester.

    To get a good read on it you'll either need a digital scope, a microcontroller, or one of those handheld jobbies.

    I think it could be done with discreet components, a 555 and some resistors and a capacitor, but it'd be tricky.

    If I remember correctly the proper range is 200-500ms. You could almost use a stopwatch and an LED on the line (with resistor, of course, and going to ground rather than in-line) to take a reading on it. The accuracy would not be good, but it ought to be enough to tell you whether it's in the right ballpark.
    My Dad's got a digital scope but I don't have a microcontroller, although I might have some 555s lying around (I'm always buying parts for projects I never get round to doing, or I just buy a few spares as they're cheap and the shipping isn't). I'll see about testing it with a resistor and LED though.

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