pc power supply

Discussion in 'Computing and Networks' started by gen12, Feb 5, 2013.

  1. gen12

    Thread Starter New Member

    Feb 5, 2013

    This is my first post here.

    I have a brand new corsair hx850w desktop power supply, I bought it from someone so it is not under warranty.
    From the first time i plugged it in, it didn't start unless I give it a little tab or nudge. I put it in my pc case and used it normally, it worked just fine, and tested the voltages with a multimeter it was very accurate. Sometimes it won't start unless i give it a little tab. After like a month, it won't start with a tab, so i got the psu out of the case and then a tab it worked, but if I flip it over it won't work unless i put it back to the other side.
    After 2 days, it won't work whether with a tab or not or putting it on any side.
    I took it to an electronics repair shop, he checked it and told me it is still brand new, with no troubles whether in the board or any capacitors, he checked soldering points on the back of the board and the front, but there are no problems. He is trying everyday but can't seem to catch the problem.

    So the big question, what do you think the malfunction so i can tell him to check?, because @ that time he is open to all suggestions.

    Please help, the psu is still new and it is a waste not to work again.

    Thanks for your help in advance.

  2. electronis whiz

    Well-Known Member

    Jul 29, 2010
    welcome to the forums

    it sounds to me like possibly a failed transistor or IC. for testing purposes I never connect it to a system. should something go wrong you may fry your whole computer. i'm guessing it's an ATX or newer variant. you take the 20 or 24 pin motherboard connection. on the side with the clip 4th wire in from the right side with clip up end facing away(pin 16) this should be a green wire. connect this to a black ground wire and it will turn on then use a DMM to test it.
    is the voltage set correctly on it? the little slide switch changes it from 120 to 220 if not correct it won't work. also try difrent power cords some supplys have problems with certain power cords, not sure why, but they just don't fit very well together and a bump can turn it on or off.
    test the switches including any on/ off for it. look for heat damage to any parts. I have seen some that failed because the fan stopped, and others it could just be a diode, resistor failing.
    when I look at something like that I always work from the supply side then to the output side. check the bridge rectifier, transformer, driver transistor, opto isolator. most of these are pretty easy to test using just ohm meter, but the opto isolator could be a bit harder. I haven't seen one of these fail, but this would prevent it from running. this has something to do with providing feedback to run the transformer. this is usually a small 4 pin ic looking part normally close to the transformer. 2 leads on output side other 2 on input side.
    (working on a PSU is not exactly a good idea because the filter caps can kill somebody. I take no responsibility should somebody get shocked.)
  3. luvv


    May 26, 2011
    By "Tab" are you referring to the 110/220 select switch?

    Furthermore,testing PSU w/ Multimeter isn't really representative of it's health.

    You may need a load on it for the problem to present itself.

    These are cheap and do just that http://www.newegg.com/Product/Produ...eId=1&Description=power+supply+tester&x=0&y=0

    Simplest solution is contact the seller and get his warranty info, Corsair has one of the best.
  4. tinamishra

    New Member

    Dec 1, 2012
    Hello I have corsair hx850w and when i plugged in i got a little blast with smoke and then it stop working so what actually happened? can some body tell me what should i do in this situation?
  5. jaygatsby

    New Member

    Nov 23, 2011
    Why isn't it under warranty? I had a Corsair PSU fail due to "short" between my apartment 110 and 220 (in Korea), and gave it to a buddy... he turned it in for exchange, directly to Corsair.
    tinamishra likes this.
  6. ScottWang


    Aug 23, 2012
    If you can disassembly the power from PC, and then open the case, check the capacitors from biggest one, to see does anyone was raised on the top, if you can see that then the cap has internal explosion.
    Replace all the caps if they has any raised.
  7. jaygatsby

    New Member

    Nov 23, 2011
    Why replace all?
  8. ScottWang


    Aug 23, 2012
    Replace all the capacitors, that is a lazy way that I called, that is without thinking and no any special skills needed.

    Repairing a device that depending on what's your puepose, if you just want to solve the problem easier and quickly, that is one kind of mathods to do, if you want to find out where the problem is, then please don't do this way.

    When you want to repairing a PC PSU, if that PSU is too old, sometime even the new PSU also has the same problems, because the PSU price is too cheap, so the reason one is the quality of many capacitors of PSU is not so good, the second one is the rating voltage of capacitors is too low, they used the rating voltage close to the working voltages, as a rating voltage 6.3V used in a 5V circuit, or the values of filtering capacitors is too close to the calculation requied, it should be over the values of the calculation requied some more, otherwise it will causing the circuit in a astable status, and it could be damaged the parts.

    When you want to repair a PSU, you still have something to be considered:
    1. How is the brand of your PSU, is the brand good, Reliable?

    2. Does the PSU is too old?

    3. Do you have enough knowledges to know how to repair a PSU?
    it depends on your abilities.

    4. If you don't have enough knowledges to repair the PSU, then when you find a cap already explosion or raised, it could be some other caps still have some problems, you could just replace the explosion or raised one, when someday cames that it will explosion or raised some others.

    5. If you got the good skills to repair the PSU, then you can measure the voltages and currents and their waveforms, you can just replace the bad caps, although some other caps you can't see anything wrong, but actually they already damaged, unless you unsolder it, otherwise you can find it.

    6. I'm not Encourage anybody to replace all the capacitors, but when the PSU is too old, or the PSU is called : white brand, or you don't have enough skills to repair the PSU, or already has 3 capacitors explosion or raised, so sometimes replace all the capacitors is a good way to solve the problems.

    Here was some damaged capacitors, some was exploded, some was when they solder on the PCB, I can't see the problems, but when I unsolder them from PCB and then they really shocked me, because their pins were destoried by electrolyte.

    ▽ This Power is a part of Hub, Left 3 caps look ok, right 3 caps was exploded.

    ▽ Right 3 caps look ok, left 3 caps was exploded, when they was on PCB

    ▽ Enlarge the image, those caps look ok when they was on PCB.

    Once that I bought some capacitors from the local store, I didn't check them when I just buy them, but when I want to take them to replace the damaged caps, I found they was all raised, I can't believe it that happened to me, I felt that should be something wrong, the caps must had some problems, because the local store that I were their regular customer, so when I went to the store, I asked the boss to took the same caps to check, wow, all of them already raised, oh, that's the problem was, and then they replace the caps for other brand to me.
    Last edited: Feb 12, 2013
    jaygatsby and tinamishra like this.
  9. tinamishra

    New Member

    Dec 1, 2012
    Thanks for suggesting me and giving me such a useful information.