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Capacitor Value issues (simple)

Discussion in 'General Electronics Discussion' started by RandyTWarris, Jun 22, 2013.

  1. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    I'm very new to electronic circuitry and currently only started repairing equipment as a "work" hobby and just got stumped on this HF coupling capacitor.

    In line with the tweeter's positive line there were two capacitors paralleled together, the leads broke off and they appear to be a silver mica capacitor or possibly a polyester film capacitor.

    The important aspect is the value as they need to be changed because the leads are completely severed.

    They are rather large and old, blue colored in a really hard enamel-like substance and has the writing:

    Ti
    12K100V
    Mexico

    Just like that.

    I'm predominantly only used to 3 digit codes or plain printed.

    Thank you!
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    I believe that would read 1.2uF rated @ 100V but a photo would confirm it. Put a penny next to them for size reference.

    EDIT: Welcome to EP. ;)

    Chris
     
  3. duke37

    duke37

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    Jan 9, 2011
    12000pF or 12nF?
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Actually, I think you're correct. I misplaced the decimal point! My first clue should have been that the OP thinks it's a Silver Mica.... Duh!

    Chris
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Just for diversity of opinion... I doubt that the k means kilo-picofarads; K on capacitors normally means 10% tolerance. I've never seen it used to mean "thousand" on any component marking. Only on some old schematics.

    In that case, the capacitors would be 12 pF, which is far too small for tweeter coupling capacitors. I guess it could be 12 uF but that seems pretty high for a tweeter coupling capacitor. Or maybe the OP has omitted a number at the start?
     
  6. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    This is a picture of the capacitor with a penny for reference.

    Hopefully this helps!
     

    Attached Files:

  7. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    As you can see both leads are broken off.
     
  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    It looks pretty big. I don't know how big a penny is (and the Wikipedia article doesn't help); perhaps a ruler would have been a more international reference!

    My guess is it's 12 uF. I thought it might be 1.2 uF with the decimal point not printed properly, but there's no room for one.

    I guess you could always borrow a capacitance meter and touch the probes onto the little bits of metal you can still see. That would clear it up.

    If it's 12 uF here's a suitable replacement from Digikey: http://www.digikey.com/product-detail/en/B32794D3126K/495-4141-ND/2182159
     
  9. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    A penny is 19.05mm in diameter or 0.75 (3/4) inch.

    Edit: I'll try to get a picture with a ruler :p
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    That's OK, I get the idea.

    It's impossible to say for sure. I think it's probably 12 uF but I think you should try to borrow a capacitance meter. Perhaps take your capacitor into a shop that sells multimeters and ask them if they'll measure it for you.

    That might work here. I don't know how obliging sales staff are around your way.
     
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    I'm through guessing because what I thought was an educated guess is looking more and more like just a plain old guess. We don't usually do that here. ;) .

    Chris
     
  12. davenn

    davenn Moderator

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    Sep 5, 2009
    NO really?? hahaha

    Dave
     
  13. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    Ok so I finally bought a capacitance meter (local shop wouldnt let me just use theirs) and it is 12uf and 100v with a 5% tolerance.

    Im not sure what kind of type it is, i thought possibly silver mica or film but it is polarized so maybe a weird electrolytic?

    Tyler Warris

    (thank you for the help thus far!)
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Not sure exactly how big a penny is (here they were about an inch across before they were phased out in 1966).

    That capacitor looks like a greencap (metalised polyester film).

    1.5uF is a large value, but not that unlikely
     
  15. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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  16. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    Yeah, it will only read capacitance from my meter in one direction, so I am presuming it is polarized,or broken lol
     
  17. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    That doesn't make sense. Try it again and make sure both probes are making good contact both ways round.
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Capacitance meters use very low voltages (typically) and even electrolytics which are very sensitive to polarity will test fine both ways.

    If it really doesn't work one way around, measure the resistance one way then the other.

    I've never heard of a fault that introduced diode action, but like the existence of the Loch Ness monster, I can't rule it out.
     
  19. RandyTWarris

    RandyTWarris

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    Jun 22, 2013
    Well, I got it looked at by a someone nearby whom works on fixing audio electronics. From what he said it is a 12uf 100v 5% tolerance film capacitor which is bipolar.

    As far as the polarized aspect of it, I was simply just testing it with poor contact hence it wasn't reading right.

    Thank you everyone though! I ordered a replacement and got the High Frequency capacitors changed out and it works like a charm.

    Tyler
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    This is going to make us all feel better because capacitance in only one direction didn't make sense,

    Chris
     
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