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Desktop Computer With Intermittent Power Problem Fixed

By on September 9, 2015
cpu motherboard repair

 

 

 

 

 

 

 

 

I have received one desktop computer with the complaint of intermittent power problem. Hence I have started troubleshooting by testing the On/off power switch of the computer with my multimeter and found it to be good. Then I have started visual inspection in desktop for any loose connection but everything was ok. I have doubt of the ATX SMPS, hence I have put my working test bench SMPS for testing but still the problem was there. It sometimes works and sometimes don’t.

I have observed whenever problem occurred at that time, the CPU FAN and SMPS FAN both were working that means something is wrong with motherboard because power is available on motherboard. Hence I have removed the motherboard from the computer and again started visual inspection on the board. This Motherboard is of ASUS Make and Model is P5B-MX.

motherboard repair

While inspecting everything seems to be ok except one thing. I have observed one capacitor is little bulged.

motherboard repairing

The value of the Capacitor is 3300uF 6.3V. For your information it is difficult to find such part in our local electronics shop. So I searched through all the junk boards that I have kept and finally found one ASUS MB P5GZ-MX with identical same design of this section but capacitor value is slightly lower than the original one-680uF 6.3V. Since I can’t find the exact capacitor value, I have decided to take the risk by using the 680uf 6.3 volt capacitor and run the test.

motherboard repaired

The good news-after letting the computer run (burn in test) for 2 days non stop, it seems that this capacitor can be used. However I will continue to search for the part as the original part number is still the best if you want your machine to last long.

yogesh

 

This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.

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Note: You can check out his previous repair article in the below link:

https://www.jestineyong.com/speaker-intermittent-problem-repaired/

 

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30 Comments

  1. Anwar Shiekh

    September 9, 2015 at 8:22 pm

    Intermittent problems can be the hardest; but a bulging capacitor is a great help,

    Likes(3)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:17 pm

      Yes lucky to get clue!!!

      Likes(0)Dislikes(0)
  2. Gerald Millward

    September 9, 2015 at 8:26 pm

    Not all bad Electrolytic capacitors give a physical clue by bulging or leaking etc. In this case, do you have a strategy for further investigation of the fault?

    Likes(1)Dislikes(0)
    • Gary

      September 10, 2015 at 5:18 am

      Esr meter - Justine Yong sells the blue meter - i wouldnt be without one now!

      Likes(0)Dislikes(0)
      • Yogesh Panchal

        September 10, 2015 at 6:25 pm

        Gary, you are right.

        Likes(0)Dislikes(0)
    • Feeshy

      September 10, 2015 at 6:59 am

      Gerald, the best test is for ESR. A bad ecap usually has high ESR. When they bulge, it's as if it is shouting "Change ME first!" Great Job Yogesh! Right now I have a motherboard that has more than 10 ecaps that are bulging. Waiting for my order of all new caps to arrive. I'm gonna change them all.

      Likes(0)Dislikes(0)
      • Yogesh Panchal

        September 10, 2015 at 6:27 pm

        Hi Freeshy,
        Good luck to you.

        Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:20 pm

      Thanks for your comment.
      This MB is working fine till the date hence no further investigation is required yes if problem is persist then definitely this led to some another problem.

      Likes(0)Dislikes(0)
    • Paris Azis

      September 12, 2015 at 1:11 am

      Hello Gerald

      I have the feeling that you are misunderstood.
      You obviously mean a strategy for resolving the intermittency problem of the mobo and not how to test it for bad caps. Anyway...

      Best Regards

      Likes(0)Dislikes(0)
  3. cnwhyte

    September 9, 2015 at 8:41 pm

    you're a genius sir. Thanks

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:22 pm

      Thanks for your comment.

      Likes(0)Dislikes(0)
  4. Allan

    September 9, 2015 at 10:02 pm

    Like Anwar says intermittent problems are tough to solve, but if you see a defective component it is of great help. Keep up the good work Yogesh!!! We learn alot from you guys.

    Likes(1)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:23 pm

      Thanks Allan.

      Likes(0)Dislikes(0)
  5. Robert Calk

    September 9, 2015 at 10:05 pm

    Thanks, Yogesh. You didn't have a larger capacitance e-cap that was rated for higher voltage? It doesn't have to be a 6.3V.

    Likes(3)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:32 pm

      Sir,
      You are right but size of capacitor is also important.

      Likes(0)Dislikes(0)
      • Robert Calk

        September 11, 2015 at 10:31 pm

        But the replacement was smaller than the original in size also.

        Likes(0)Dislikes(0)
    • Paris Azis

      September 12, 2015 at 12:31 am

      Hello Robert

      I agree with you. See my comment below.

      Best Regards

      Likes(0)Dislikes(0)
  6. Merlin Marquardt

    September 9, 2015 at 11:25 pm

    Bad caps, good repair. Higher capacitance replacement capacitor is not a problem?

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:34 pm

      Thanks for your comment.
      But i didn't try yet.

      Likes(0)Dislikes(0)
  7. Humberto

    September 10, 2015 at 1:18 am

    Good repair Yogesh. Sometimes you have to solve the problem taking into consideration some ideas as you did.

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:35 pm

      Humberto,
      Thanks for Comment.

      Likes(0)Dislikes(0)
  8. Gopal Sharma

    September 10, 2015 at 10:42 am

    Thanks for sharing. In mobo lots of capacitors are there in vcore voltage in parallel. How to check ESR on board in that case. Is there any tips or i have to remove one by one and check.

    Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 10, 2015 at 6:36 pm

      Sir,
      it is always advisable to check the components out of circuit.

      Likes(0)Dislikes(0)
    • Paris Azis

      September 12, 2015 at 12:44 am

      Hello Gopal

      It is very easy to check the total ESR pf parallel connected capacitors. Simply measure their total ESR and get the total picture of their status. Then, simply again, use your brains and estimate this result you have in hand. Note that a single 3.300μF cap, will measure near 0,01 Ohms, that is 10 milliohms. Then, if for example the device under test uses two caps in parallel, their healthy (anticipated) condition should give you 0,00 Ohms, that is, a short circuit indication. And this is because we have a "divide by two" condition, due to their parallel connection. Therefore if you have an indication in your ESR meter of say 0,1 Ohms as a result of five parallely connected caps, then it is obvious that their health is bad. Only then (according to my humble opinion) it is necessary to desolder and measure each one of them in order to find defective pieces among them. Not in advance.

      Best Regards

      Likes(0)Dislikes(0)
  9. Paris Azis

    September 11, 2015 at 4:36 pm

    Hello Yogesh

    A good visual inspection many times leads to a fast repair. Nevertheless the repair needs to be successful as well! So, be aware that this mobo will very soon revisit you again for a new repair and for the same capacitor. And this is due to the fact that the new capacitance is reduced by a factor of 4,85 times in comparison to the original value, which simply means that the new much smaller capacitor will not be in position to withstand the heavy ripple currents that it is supposed to absorb and secure smooth d.c output. This in turn will result in high increase of its inner temperature which then will very soon cause rupture of either the safety rubber valve on its bottom or violent rupture of its upper aluminum case or even both of them, depending purely on its internal pressure at that time. Therefore the rule always is; “never undervalue the replacement capacitors both in rated working voltage and capacitance”. If you (slightly) overvalue is not a problem, but not the opposite. Finally, there is always a good reason that the designer of the circuit specifies every component of it.
    Thanks for sharing your experience.

    Best Regards

    Likes(2)Dislikes(0)
    • Robert Calk

      September 11, 2015 at 10:28 pm

      Thanks Paris. Your comment is much more eloquent than mine.

      Likes(0)Dislikes(0)
    • Yogesh Panchal

      September 14, 2015 at 12:00 am

      Sir,
      I agree with you and Robert sir and thanks for your suggestions.
      I have compared the similar section of both the MB and I found similar components in this section except this capacitor hence i have took the chance. Anyway i have repaired this board and period of say around two moths still it works fine without any problem.

      Likes(1)Dislikes(0)
      • Paris Azis

        September 15, 2015 at 12:20 am

        I am glad that you agree Yogesh.
        Note please that I did not deny the fact of the board repair by you. I only consider that the element of reliability is missing from this repair, rendering it unsuccessful according to objectively valid standards about a successful repair.
        These two months of unproblematic function of the MB you refer to, mean practically nothing, because I don't know after how many years of normal operation, from the first time it was put in operation, this MB revealed this failure, in order for me to make a reasonable comparison.
        "Keeping the analogies" therefore, I would expect that the same failure would appear again after a time duration of about five times earlier compared to the time it appeared for the first time. In other words, you found the cause of the problem but its cure is still incomplete. That is all I am saying. Anyway I already took in account the last phrase of your text before even putting my first comment.

        Best Regards

        Likes(1)Dislikes(0)
  10. Delelegnbelayneh

    September 13, 2015 at 10:42 pm

    it is a wonderful explanation I understand perfectly

    Likes(0)Dislikes(0)
  11. Gurpreet

    September 19, 2015 at 1:28 pm

    Thanks for sharing this article.

    Likes(0)Dislikes(0)
  12. Momchil

    September 22, 2015 at 3:09 am

    It's funny you say "little" when it really has around 5 times lower capacity!!! 😀
    3300uf are pretty standard caps. It would've been a lot closer to use 2200/6.3 which are also standard.

    Likes(0)Dislikes(0)

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