Connect with us

Monitor lcd turns black after few seconds

Discussion in 'Troubleshooting and Repair' started by 4rc, Feb 8, 2014.

Scroll to continue with content
  1. 4rc

    4rc

    5
    0
    Feb 8, 2014
    Hi, I probably do not have even the basic electronics skills required. To post in aforum like this, but when i can try to fix smthg opening it I always try. I have a PB led monitor some years old that turns blank after a few secs after i plug it to the power plug. In this two seconds of functioning it dispalys thr scanning menu, so it seemed to me not a severe problem. I supposed it was smthing elecrical, like a capacitor or a peak protection system that caused the monitor to fail and opened it hoping to find a detached cable or smthg visibly damaged. But obviously I. Didn't and now everithing looks the same to my eyes. Is there a component that i should check at first? I have a cheap tester and i can solder and unsolder. Thanks to everyone who read until this point and to whom can give me some piece of advice.
    FabriZio
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    There's 2 caps on the second image (the power supply) that have bulging tops. I'd replace both of them at least.

    Thanks for posting such clear photos.
     
  3. 4rc

    4rc

    5
    0
    Feb 8, 2014
    thank you for your quick reply. the caps you mean are these two?
     

    Attached Files:

  4. davenn

    davenn Moderator

    13,662
    1,889
    Sep 5, 2009
    yup, those 2

    cheers
    Dave
     
  5. 4rc

    4rc

    5
    0
    Feb 8, 2014
    I managed to remove the 2 caps with only a little electric shock caused by the residual energy in the 400v guy... :) in the next few days i'll look for the new components, they should be quite common ones, being 2 16v one 680uF e the other 330uF. While desoldering i caused the lead to touch another soldering, and then I worsened with a knife trying to separate... is it going to be a serious issue? How may I fix it? I post the pic of both sides. Thank you!
     

    Attached Files:

  6. davenn

    davenn Moderator

    13,662
    1,889
    Sep 5, 2009
    OK
    have a look at the pic I posted ... your second pic

    [​IMG]

    Note 1 ... all the area in the blue boundary is all part of the same circuit connection
    just smooth out the long solder ridges with your soldering iron

    Note 2 ... inside the red circle, just make sure that there is no little trace of solder
    across that gap ... it looks like there may be


    cheers
    Dave
     

    Attached Files:

    • pcb1.jpg
      pcb1.jpg
      File size:
      99.7 KB
      Views:
      231
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    When you get replacements, make sure they are 105C rated. The lower temperature rated (85C) capacitors will fail sooner. In general, a higher voltage rated part will also be better -- if it physically fits)

    Looking at the traces here, I think that Low-ESR capacitors would also be a benefit.

    If there are any issues with clearance, you might want to make sure the replacements are not too tall.

    Before you solder the replacements in, make sure you have them around the right way as they can fail -- sometimes explosively -- if you connect them around the wrong way.

    Sorry about that 400V capacitor. We should have warned you about that. They can give a nasty bite. I normally use a few choice words and have been known to fling whatever I'm holding across the room -- I'm sure you'll agree it's not as funny as it sounds.
     
  8. 4rc

    4rc

    5
    0
    Feb 8, 2014
    Goood work!

    Hi guys,
    I bought the caps and placed a 25v in place of a 16v, cause at the store they had no 16v and told me it was the same. After some confirmation googling and a quick polarity search I managed to have it working again. The leak of the circuit lead on the other sector seems to me only a scratch. Everything seems to be fine and working! Thank you all!
    Fabrizio
     

    Attached Files:

  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,780
    Jan 21, 2010
    You probably need to practice your soldering, but good job :)

    In the first image, the top set of joints look better than the bottom.

    On the bottom set, the one on the left has too much solder, but it probably OK.

    The one on the right is potentially a dry joint. Notice how the solder has not flowed over the pad. This is a bad sign. Perhaps all you need to do is to touch the soldering iron to it again, long enough to melt the solder so it flows over the wire and the pad.

    I also wouldn't have splayed the leads so far. It makes it a bit harder should you need to remove these again.

    You'll find out how good these replacement capacitors are by the time the failure takes to repeat itself :(
     
  10. 4rc

    4rc

    5
    0
    Feb 8, 2014
    I knew it was not a so clean job, but it seemed to me that it was let's say sufficient. I was afraid that trying to improve could actually worsen the already damaged sector. I'll let you know if I hear some popping so far! I post the last macro for perhaps a better view.
    Thanks again and i'll be back as soon as smthing else breaks
    Fabrizio
     

    Attached Files:

Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-