Replaced PSU after 115 to 240v overload

By TDUK ยท 8 replies
May 6, 2009
  1. Gateway DX4200
    AMD Phenom 9550 Quad Core (Fox Bengal motherboard)
    Orig PSU LiteOn 300w
    Replacement PSU Trust 370w

    Definately a novice here so any advice will definately be appreciated. I relocated to the UK from US. Switched the PSU from 115 to 240 but for whatever reason (i don't think the toggle had completely slid to the 240 position). I burnt out the PSU at the capacitors. I have replaced the original 300w PSU with a 370w. The original PSU had the 4pin cpu +12v connector with a max output of 13A. The new PSU max is 15a. The amps may or may not be important but this lead seems to be the epicenter of my current predicament.

    Here is the problem: when connecting the 4 pin lead the system led light comes on and is attempting to power up, the cpu and case fans engage but it quickly goes off. I can hold the power button on but it will only turn on and off and only runs for about a second each attempt. if the 12v is not connected, but I leave the 24 pin lead connected, the led light indicates that it is in sleep or standby. in either case, their seems to be no boot up at all. there is no signal being sent to the monitor to indicate activity at the motherboard or even that the bios is booting.

    Have I fried the motherboard?
  2. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    Actually Amps don't matter (well they do and they don't)
    Basically Amps are pulled by the load, if the load only requires up to 13A (of course it won't be that high though) the Power Supply will only supply that amount ie 13A

    By the way, it's not the same though when people touch live AC circuits though, because they make an excellent bridge from positive to negative, this pulling the maximum amount of Amps available ie 15Amps (mind you it only takes 5 amps to well kill you, not mA (miliAmps) as some think, as this would need to pass through the resistance of your body first, then 15mA would do it ;))

    Just to add more confusion the rated 15A is actually DC, therefore we can touch the wires past the Power Supply, ie the Motherboard

    So back to topic :D

    Amps won't matter, although higher Amps on a Power Supply makes a stronger Power Supply (it can basically put up with more)

    Firstly check with another working Power Supply
    Then that's it, faulty Motherboard :(

    lol, I answered this entire thread with those two short lines :)
  3. Rage_3K_Moiz

    Rage_3K_Moiz Sith Lord Posts: 5,443   +38

    @TDUK, you have most likely fried your motherboard. All the stuff you have reported is symptomatic of the motherboard not working.

    I didn't quite get what you meant by this Kim.

    Not at all! Currents as low as 20mA are enough to cause muscular paralysis and breathing cessation. Currents approaching 100mA will completely stop breathing, and death usually occurs at currents between 100-250mA, where heart fibrillation occurs.
    Strangely enough, values beyond this range are marginally safer, since the current is high enough to cause the heart to stop beating completely, and provided defibrillation can be done quickly enough, the victim can be revived.

    Oh, and before I forget, the above applies only to 60Hz AC. The human body can tolerate higher values of DC (upto 100mA) before any harmful effects are felt.
  4. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    You may have missed this part ;)

    I was always told less than 1 Amp can kill you (and obviously it's way less ie mA)
    But then I found info that mii amps will not pass through your body well enough (from outside to in)

    Actually 8 mA passing through the heart will kill you
    But you need up to 5 Amps to get it through the fat, tissue and skin first
    Look it up
  5. Rage_3K_Moiz

    Rage_3K_Moiz Sith Lord Posts: 5,443   +38

    Ah, but body resistance changes depending on the medium through which the electricity is conducting, as well as the surface area of the part in contact with the conductor and if there are one or more parallel connections between the body and conductor. Also, the dimensions of the conductor, as well as other conditions such as sweat on the skin and clothing material, change the electrical resistance.

    The values I have given are for the most typical contact points i.e. the hands and feet.

    Also, as a rule of thumb, I consider any voltage above 40V to be capable of delivering dangerous shocks.

    I think that would be enough information for the OP, no? ;)

    Later Kim. :)
  6. kimsland

    kimsland Ex-TechSpotter Posts: 14,523

    Ok but just because....

    Voltage obviously does not cause problems, (unless it's some big flash Voltage way over 40V)

    Amps do ;)

    Now that's the end. :p
  7. captaincranky

    captaincranky TechSpot Addict Posts: 13,029   +2,558

    Actually, micro amperes have the potential to do you in, but this is in the context of it being delivered sub-Q. Make note of the tiny paddles they use to "restart" the heart after open heart surgery. Something on the order of 10 Watt-seconds, as opposed to the 300WS charge of a standard defibrillator.

    The reason we can "touch the wires" past the PSU is because the "voltage" has been reduced. Voltage is EMF "pressure" so the "pressure" has been much reduced. High voltage DC can be lethal also, as I believe that current flowing in one direction is more prone to cause a "no release" situation, wherein the muscles lockup. You can touch a standard 9 volt battery (ie as in smoke alarm battery) to your tongue, fairly annoying, not lethal. Low voltage and low current.

    Since DC cannot be transmitted over long distances, you don't encounter high voltage DC as frequently as HVAC. Trust me, the B+ voltage of a tube amplifier such as one might encounter in a guitar amp, (frequently in excess of 350 volts), will light you up big time!

    Any voltage must overcome the resistance encountered by it passing through the human body. Skin resistance drops the voltage and the current entering the body, and while salt water is a fairly good conductor, it's not copper. That having been said, it is a good electrolyte, much better than plain water.

    Oh, and a defibrillator actually kills you, but just for an instant.

    You may not be always right, but you're never wrong.
  8. TDUK

    TDUK TS Rookie Topic Starter

    thanks to everyone on the info regarding amperage and it's effects on the human body and mortality.

    Thank you to rage_3k_moiz and Kimsland for the technical answer regarding the motherboard. Not the best news, but it was the conclusion I had come to as well.
  9. Tedster

    Tedster Techspot old timer..... Posts: 6,002   +15

    is your cpu got power to it? If you overloaded the system, possiblity something else is burnt.
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