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  1. #21
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    Re: PC power supply short circuit

    What I want to know for now is how each output is handled?

    I mean I used to see rectifying diodes after the high frequency transformer, now I don't see anything!

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    - - - Updated - - -

    I opened the cooler master webpage for the 650V semi modular and found an interesting information.

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    So I only have one line after the high frequency transformer, because I saw the pins after the transformer are shorted and only one ground, that's my guess for now.

    But why two coils?
    Last edited by eagle1109; 17th August 2017 at 05:12.



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    Re: PC power supply short circuit

    Hi,

    If those are "custom DC/DC modules" then isn't it obvious?
    Two output voltages --> two DC/ DC converters --> two coils

    Klaus



    •   Alt17th August 2017, 06:38

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  3. #23
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    Re: PC power supply short circuit

    Yes two coils for 3.3 and 5 volts.

    But going back to the two coils near the high frequency transformer and the two after before the "custom DC/DC modules", because these modules come at the final stage just before 3.3V and 5V.

    So, there's only one main non-rectified voltage after the high frequency transformer, then this line is distributed to two lines. One to feed the "custom DC/DC modules" and the one which is the biggest one I guess is the 12V which doesn't have a "custom DC/DC module", I think it goes to the 4x power MOSFETs near to the "big yellow taped transformer".

    And that's why the 12V is rated at 54A.


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    But what also I don't understand is how all these lines are rectified? I think the many capacitors and also the aluminum capacitors are the reason, so much more capacitors are the substitute of rectifying diodes.

    Another question, why the total power is summed at 650W where the ratings are 120, 648, 3.6, 12.5 watts which is 784.1W?
    Last edited by eagle1109; 17th August 2017 at 06:59.



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    Re: PC power supply short circuit

    Hi,

    The coils have been discussed before:
    * input filter
    * PFC
    * high power path
    * standby power path
    * some smaller maybe for just for reducing ripple voltage (LC filter)

    Why the power is not added up:
    Because some depend on each other and some don't. And it depends where in the circuit the limiting happens.

    Klaus



    •   Alt17th August 2017, 07:11

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  5. #25
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    Re: PC power supply short circuit

    Is my guess right that there's no diodes and they are using caps instead?

    If that's true then I should takeout the caps, but the soldering material is very strong and I only have 30W soldering iron.



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    Re: PC power supply short circuit

    Is my guess right that there's no diodes and they are using caps instead?
    No, that wouldn't work. I think the "custom DC-DC module" is just advertising hype for "a coil on a small PCB to save space" as the name implies it is already DC entering it and it is therefore already rectified by diode(s) and filtered with capacitors.

    The power rating is confusing but what it tells you is the individual rating of each output when used alone. The 650W limit is the total the power supply can manage across all the loads, meaning they can't all be run at full load at the same time.

    Did you try the resistance tests I mentioned in post #20 yet ?

    Brian.
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    Re: PC power supply short circuit

    Quote Originally Posted by betwixt View Post
    No, that wouldn't work. I think the "custom DC-DC module" is just advertising hype for "a coil on a small PCB to save space" as the name implies it is already DC entering it and it is therefore already rectified by diode(s) and filtered with capacitors.

    The power rating is confusing but what it tells you is the individual rating of each output when used alone. The 650W limit is the total the power supply can manage across all the loads, meaning they can't all be run at full load at the same time.

    Did you try the resistance tests I mentioned in post #20 yet ?

    Brian.
    Yes but not entirely, there are many SMD low ohms resistors, but there are ones with numbers; like, 417 and reads low resistance. But, obviously that because of the short which affects the resistors, capacitors and the MOSFETs.

    What I want to do now is to take those aluminum caps, and go from there by taking out components until I find the faulty one. But the soldering is so strong. I would give it a try now and see what can I do or I should go today and buy 60W.

    What you suggest to me 100 or 60W for this work? I consider the soldering here is so strong, it doesn't melt so easily.



    •   Alt18th August 2017, 05:48

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    Re: PC power supply short circuit

    I use a 45W soldering iron without problems.

    Please do those resistance checks - all I need is the resistance from the +12V to 0V in both directions. I appreciate you have done the buzzer check but you must understand that the buzzer makes sound not only for a complete short but for any low resistance. Try probing a good 10 Ohm resistor for example and it will say it is shorted. In the 12V output it is normal to find low values so the buzzer may be sounding when there is no fault there. A resistance test is more accurate, it gives an actual reading of the components and will tell if a short is really there or you are seeing normal operation.

    I strongly suspect you are looking in the wrong place and the fault lies in the switching circuit.

    Brian.
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    Re: PC power supply short circuit

    I agree with Brian. You may be looking in the wrong place, and you're certainly using the wrong tool (buzzer) to debug this. If you don't have an oscilloscope, I suggest maybe you should just buy a new power supply.

    'If your only tool is a hammer, all your problems are nails.'



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