Soldering a capacitor need help something went wrong

Discussion in 'The Projects Forum' started by zorgan, Apr 15, 2012.

  1. zorgan

    Thread Starter New Member

    Apr 15, 2012
    9
    0
    I had a problem, I soldered two capacitors on this TV PSU

    when I went to snip off the excess pins on the cap one of the solder joints came clean off taking I think the hold tracking, is this actually repairable or do I now need to buy a new PSU for the TV?

    http://i41.tinypic.com/akykhu.jpg

    pic here so you can all see the MESS I made :(
     
  2. k7elp60

    Senior Member

    Nov 4, 2008
    478
    69
    You do not need to get another PS. This problem is repairable. I have put red box around the pad. It appears that the lead that you cut that is shown next to the pad with the red box needs to be carefully cleaned. If you use a small knife or a piece of fine sand paper to clean the two surfaces(the flat and the circular). Then heat up the pad that I have outlined, use some solder wik to remove the solder from it. Place the pad back on the wire you cut and resolder that joint and the joint on the other end. If that doesn't work replace the pad with a small bare wire from the wire you cut and the wire at the other end of the pad. Make sure both the new little wire and the two existing ones are soldered.
     
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  3. CVMichael

    Senior Member

    Aug 3, 2007
    416
    17
    I don't think it's such a big deal... it looks like the copper is further around the pin, so just scratch the green layer around, maybe bend the pin to reach the copper, and just solder it...

    I edited your picture to show where the PCB copper is (with red), and the area where you can scratch (with Green) to solder the pin wire.
     
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  4. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    You did two things that created the problem. First, you kept the copper foil hot for too long which destroyed the thin layer of epoxy bonding it to the fiberglass. Second, you soldered the lead while the capacitor was not seated flush to the board then pushed it down after the solder was frozen. This happened because you were soldering to the circuit board's ground plane, a large area of copper that sinks away your iron's heat. The correct method is counterintuitive since the damage is caused by too much heat but to solder to large heat sinking bodies of copper you need a hotter iron, one with more thermal mass, or to use two irons for the joint. Your solder joints also need more flux. I'm guessing you only used what was in the solder. It wasn't enough.

    To repair the damage, scrape the solder mask off of the copper area around the hole, flatten the copper, clean with alcohol and apply a repair donut (CF2 in the link below). Then flux and solder again.

    http://www.philmore-datak.com/mc/Page 271.pdf

    Also, check out this video on soldering.

    http://m.youtube.com/watch?v=I_NU2ruzyc4#/watch?v=I_NU2ruzyc4
     
    Last edited: Apr 15, 2012
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  5. P-MONKE

    Member

    Mar 14, 2012
    83
    5
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  6. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    I know, you brits are uncomfortable with the American pronunciation of the word because of what it sounds like in your vernacular. We can't figure out where you get the extra 'i' you put in aluminum. Whole books have been written about the "divided by a common language" phenomenon. Fortunately, it's mostly a source of mutual amusement. :p

    http://www.amazon.com/gp/aw/d/0966094573
     
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  7. zorgan

    Thread Starter New Member

    Apr 15, 2012
    9
    0
    KJ6EAD you really know your stuff - really impressive thanks for the reply.

    I want to thank each and every person who replied to my issue, I have learned some great and correct advice here, I will tell you what I ended up doing as I had not read the replies before I continued with re-applying the job.

    The PC Board repair kits look interesting, never seen anything like this before, I have noticed on fleabay there are some copper conductive tape but I doubt this is the same kind of thing? I was doing some googling to see if I could find anything close to what you have on this PDF catalogue but couldn't find any UK suppliers of this type of thing.

    I cleaned with a toothbrush and some isopropanol alcohol

    I used a really sharp craft knife and shaved away some of the upper layer of the PCB - to expose some of the copper foil? I think it's called.

    I then tried to flow the solder over the pin of the capacitor to connect with the copper.

    I do not think I have an amazing joint ! but it does work ! (for now) :)

    I do think sometimes you have to do things wrong to know then afterwards what to do right! if that makes any sense? :)

    but next time i have any issues like this I will take 100% on board the advice I have received here thank you everyone!!!

    I gave THANKS to everyone!
     
    Last edited: Apr 15, 2012
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