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Thread: OT PC trouble - ghost in the machine?

  1. #41
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    Quote Originally Posted by MattiJ View Post
    Power supply doesn't look like worth a repair, craptastic generic junk. Hatefull amount of low quality caps and if you want to make it last you need to replace them ALL.
    rl]
    i knew that would come up....i don't think I'll bother as its quite difficult. The caps are buried under heat sinks that are bent over a 90, so it'll be difficult to unscrew the heat sinks from Fets or whatever with out unsolding the FETs. If it fails again time for a better PS that Rockfish crap

    Oh, and those caps are around the audio chip, so they are probably just there to provide decoupling on the audio output of the chip. I am betting if you looked at the data sheet you would find electrolytic caps in series on the audio lines.
    good observation. i don't even use the onboard audio. btw, what datasheet?

    You CAn guess a bit about the part by looking at the last table, the "ripple current multipliers", but it is better to stick with what is actually spec'd.
    This is where I started and you said you don't have to guess .....but you do if the question is whats the ESR at 100kHz, which is commonly used to test of caps in a circuit, and the spec sheet doesn't state it. Every cap I test around that size is well under 1 ohm except those three, as are most info I can find on ESR testing of caps. The EEE blog guy gets particular high pitched when a spots one over an ohm

    anyway, if they only effect sound output, i'm not going to worry about them
    Last edited by Mcgyver; 02-06-2019 at 12:33 PM.
    .

  2. #42
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    Quote Originally Posted by macona View Post
    Oh, and those caps are around the audio chip, so they are probably just there to provide decoupling on the audio output of the chip. I am betting if you looked at the data sheet you would find electrolytic caps in series on the audio lines.
    More likely decoupling the heavy fluctuating current demands of the PCI/E power rails. The audio chip is a CODEC

    http://www.hardwaresecrets.com/datas...aSheet_1.0.pdf
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  3. #43
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    Quote Originally Posted by Mcgyver View Post
    .....



    good observation. i don't even use the onboard audio. btw, what datasheet?



    This is where I started and you said you don't have to guess .....but you do if the question is whats the ESR at 100kHz, which is commonly used to test of caps in a circuit, and the spec sheet doesn't state it. Every cap I test around that size is well under 1 ohm except those three, as are most info I can find on ESR testing of caps. The EEE blog guy gets particular high pitched when a spots one over an ohm

    anyway, if they only effect sound output, i'm not going to worry about them
    The "datasheet" would be for the audio chip that they are for, which will set forth the minimum filtering and power supply noise/ripple requirements. That is where you would go to find out what is needed to make the chip work correctly.

    No, you shouldn't have to guess.... because only what is on the spec sheet is "real" as in a "you can count on this" type assurance. Anything past what the data sheet says is a "guess", an "extrapolation" that one needs to be careful about.

    Specifically, the high frequency performance is not very related to the LF performance, because there are construction features that matter at one frequency and do not at others. Since they give only the LF performance, it is a good bet that the HF performance is not going to be very good, just because it does not have to be.... the data sheet does not spec it.

    It could be wonderful.... you dnn't know that nor do I. But that's the point of data sheets... they say what has to be. As you have seen, the performance can vary all over, although in-circuit, you never know for sure what is affecting it, and all those readings at 100kHx may be actually bogus.

    Bottom line, they are likely in-spec, especially since the device is not new, and ESR degrades with time, as specified on...... wait for it........ the DATA SHEET...!
    Last edited by J Tiers; 02-06-2019 at 01:30 PM.
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  4. #44
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    Quote Originally Posted by Mcgyver View Post
    ... 100uf ...
    I'm measuring around.046 ohms on one, and 3 1/2 ohms on three.

    3.5 ohms is scrap bin ESR for any 100uf low voltage electrolytic. And 0.046 ohm esr is too good to be true, there is probably something parallel with the cap or your measurement is otherwise skewed.

  5. #45
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    Yeah, Page 72 of the data sheet shows 100uf caps in series with the mic and line circuits to the front panel header. I would not worry about it either way.

  6. #46
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    Quote Originally Posted by MattiJ View Post
    3.5 ohms is scrap bin ESR for any 100uf low voltage electrolytic. And 0.046 ohm esr is too good to be true, there is probably something parallel with the cap or your measurement is otherwise skewed.
    Not for general purpose parts, which those appear to be. They are rated for 2.1 ohms, with a permissible change of in some cases + 100% after a life test.
    1601

    Keep eye on ball.
    Hashim Khan

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