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Identify this capacitor

Discussion in 'Troubleshooting and Repair' started by aeopav, May 13, 2012.

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  1. aeopav

    aeopav

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    May 13, 2012
    Greetings Folks,

    I have here an overhead console circuit board for a Ford F250 Deisel. The unit displays fuel consumption figures, miles to empty, and maybe compass heading as well. There is a capacitor missing on the board I have. This image is from a posting on a Ford forum. It is of a similar board. The capacitor in question is the one just under the white arrow.

    http://picasaweb.google.com/lh/photo/Vi5VLwFFWKU-bPxJeDjCD9MTjNZETYmyPJy0liipFm0?feat=directlink



    Am I correct in saying this is a 6 volt 470pf capacitor?

    Any assistance is greatly appreciated.

    Mark

    [​IMG]
     
    Last edited by a moderator: May 13, 2012
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Sorry, the image is not visible.
     
  3. aeopav

    aeopav

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    May 13, 2012
    Apologies people, I'm a bit challenged when it comes to attaching images to forum posts like this. I have edited the post. I think the image is viewable now.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
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    Jan 21, 2010
    I can't see any identifying marks, but it *could* be.

    Any reason you're concerned that the capacitor isn't there? It's not unusual for some components to be omitted from a board. They may be for options you don't have or were found to be superfluous.

    Does your board have a fault that you think this might address?

    Or maybe does it look like the capacitor has fallen off or failed?
     
  5. aeopav

    aeopav

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    May 13, 2012
    *steve*

    Thanks for your help. The common problem with these boards is too much heat. There are many posts on the Ford Trucks forum where guys are repairing the boards by resoldering the sm resistors (680 and 620) which are coming loose. The board I have has also lost the capacitor in question. It may be I'm not clear in saying "just under the white arrow". That picture was posted to show a missing resistor, which is what the arrow is pointing to. The capacitor I'm referring to is the silver one, partly in shadow, below the arrow.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
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    Jan 21, 2010
    My guess is 47uF 6V

    470 typically means 47*10^0 = 47.

    471 would be 47*10^1 = 470.

    Note that 470 is a little ambiguous, because it could be the actual value.

    But definitely uF, not pF.

    Are you sure it's heat that is damaging those boards? If the boards were getting hot enough to melt solder, I would expect there would be some discolouration (to say the least).

    I would be more inclined to check for metal fatigue of the solder joint caused by vibration.
     
  7. aeopav

    aeopav

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    May 13, 2012
    Here is a picture of the board I actually have showing the problems it has. I think you might be right that vibration had something to do with it, although I do think this board is showing signs of excessive heat at some of the solder joints. Considering:

    1. This is mounted up side down in the truck with the components hanging from the board
    And
    2. An F250 Diesel is a heavily sprung truck with lots of vibration.

    I'm thinking a combination of heat and vibration did the trick.


    [​IMG]
     

    Attached Files:

    Last edited by a moderator: May 13, 2012
  8. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    If the two vias to the right of the caps pads are large enough you might want to mount a through hole cap in those holes, most small caps have pretty thin leads, from what I see those vias are common to the pads so it should be quick and simple if the leads fit... The through hole cap might hold better, especially if you can slightly bend over the leads on the back of the board and lay the cap flat on the board vs upright and hit it with a glob of epoxy on each side to hold it down... Do mind the polarity when installing!

    Most SMD electrolytic caps I have come across are marked with the full µF value not the pF or any base 10 abbreviation... So I'm going to say it's a 470µF @ 6v

    Highlighted vias bellow...
     

    Attached Files:

    Last edited: May 14, 2012
  9. aeopav

    aeopav

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    May 13, 2012
    Good Eye !!!

    You are absolutely right. I have looked closely and the vias are common to the pads for the surface mount cap. I'll be seriously looking into that option. I'm already contemplating the replacement of the SM resistors with some common 1/4w carbon film resistors for better heat handling.

    Thanks for the help.
     
  10. Wabajig

    Wabajig

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    Apr 14, 2012
    The capacitor is not missing, if you look closely at the solder where the cap goes the solder is bubbled up. There was no components there. Just replace the resistors, but don't let the replacement resistor set on the board leave a little air room. I would also solder up the remaining resistors, but don't spend to much time, they will crack. Also a note on your first picture, that top left component has a bad connection on the bottom of it, check yours for same. Good Luck,
     
    Last edited: May 22, 2012
  11. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    I agree. There is a smooth convex solder bump on the lands indicating it was pasted and reflowed but not populated.
     
  12. aeopav

    aeopav

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    May 13, 2012
    I really do appreciate the input fellas. My components just arrived today so I'm hoping that by the weekend I'll have the time to set down and pay this board some attention.

    Is it possible any damage would be done without the cap, if it really is needed? I'm thinking operation might not be correct but no serious damage to the board or components.
     
  13. davenn

    davenn Moderator

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    Sep 5, 2009
    but wait a minute before you say that....

    his other good board shows the capacitor present

    Dave
     
  14. KJ6EAD

    KJ6EAD

    1,114
    157
    Aug 13, 2011
    The images of boards with the capacitor present were noted as "similar" and were found on the internet, not in the OP's posession.
     
  15. Wabajig

    Wabajig

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    Apr 14, 2012
    Probably a slight design change. Hopefully the resistors are the same value in those missing places.
     
  16. aeopav

    aeopav

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    May 13, 2012
    The resistors are indeed the same values between the 2 boards. Before I started messing with it, both "missing" resistors were still on my board. They were loose and the circuit was open. I pulled both of them as they were about to fall off anyway.

    I also have confirmation that the resistor values are all the same from the Ford truck forums where many have fixed their boards and posted on how the repair went.

    I do find it interesting though, in all the posts addressing this issue, nobody else has mentioned a missing capacitor on their board, and there are many, many posts. This problem seems to be very common.

    I'm still on the fence as to whether or not I install a cap.
     
  17. Sparkchaser

    Sparkchaser

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    May 22, 2012
    I agree with Wabajig. I don't think that capacitor was ever installed. Is the Rev. number of your board the same as the one with the capacitor?

    I see those SMD caps like that fall off all the time. I truly hate them and have soldered radial thru hole caps in there place before. I doubt, and I stress *doubt* that any damage would be done without that cap if it supposed to be there and vise versa. But, do mind polarity!
     
  18. Wabajig

    Wabajig

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    Apr 14, 2012
    Unless you soldered those capacitor connection before we (on the forum) saw them, then no. You might be changing the manufacturers design characteristics. I'm glad you were observant, but I recommend for the novice and those with poor memories to take pictures while breaking open unit.
     
  19. aeopav

    aeopav

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    May 13, 2012
    Well, I finally got around to doing what I could do with this board. I want to thank you all for responding to my question on the capacitor. Ultimately, I decided to install a capacitor as I could not find an example of this board without one. I will be giving it back to the truck's owner tomorrow and we'll see what happens. I'll let you all know.

    Thanks Again,

    Mark
     

    Attached Files:

  20. aeopav

    aeopav

    9
    0
    May 13, 2012
    The board is back in my friends F250 and working just fine. Now we'll see how long it lasts! I'm hopefull it will continue to function for a long time. I added a couple of dabs of epoxy to the base of the capacitor before reinstalling it, hoping that will keep it in place longer. Everything on this board has gravity working against it.
     
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