Need help! Identify a capacitor

Discussion in 'General Electronics Chat' started by sitran12, May 29, 2009.

  1. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    Hi all,

    I need help identifying a strange capacitor in my sewing machine suppressor - apparently it has blown up some time ago and all the rolled film inside just spilled out.
    The machine is an old Brother Mademoiselle with a foot suppressor (AC) and I was able to read the following markings off the cap:

    DFCT-3
    CAP 0.1 uF
    WV 250VAC
    ---------
    B.S. G13
    SANYO

    MY QUESTION - what do all these mean, and what type of capacitor should I buy that can replace this one?

    here's also a pic (the right side has some black tape stuck to it):
    [​IMG]

    thanks!!
     
    Last edited: May 29, 2009
  2. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,535
    You are in luck, 0.1µF is one of the more common values out there, though 250V rating is a bit high, and it is non-polarized (this is important).

    Radio Shack sells a pretty close equivalent (different shape, same part) under part number 272-1053 for $1.49.

    http://www.radioshack.com/product/index.jsp?productId=2102589

    [​IMG]

    By the way, if this a house hold appliance, be careful. High voltage is hazardous.
     
  3. radiohead

    Active Member

    May 28, 2009
    474
    31
    It looks like an axial electrolytic capacitor with a value of .1 micro farads rated at 250 Volts Alternating Current (VAC). Look closer at the capacitor and see if there is a polarity marking on it. If it's a polarized electrolytic, there should be a minus sign at one end that will denote the negative lead. Sometimes the older caps have a plus sign at the positive lead.
     
  4. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    Thanks Bill and Radiohead,

    So, besides the capacitance (0.1uF) and the voltage rating (250VAC) all the other details are irrelevant?
    any idea what do the "DFCT-3" and "B.S. G13" mean?

    thanks again
     
  5. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    By the way, is there a difference between an AC capacitor and a DC capacitor?
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,535
    Yes, a nonpolorized cap (which is what you have) can take ± on either lead. A polarized cap has to have one side positive and one side negative. Most larger values are polarized, though you can find examples that aren't (they cost more and are physically larger).
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,740
    759
    I wouldn't replace that cap with a polyester one guys..if I were you.
    That blown up cap is rated at 250VAC 0.1uf is a PAPER CAPACITOR.
    I would get an identical one, u can try old washing machines, those have these kind of caps sometimes.
     
  8. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    What is the application for the capacitor?
    Is it used in the mains circuit?

    Greetings,
    Bertus
     
  9. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    The cap is in the foot control of my Brother sewing machine.

    The mains is connected to the motor which is connected to the foot control..

    The cap is inside the foot control (image of the control open and upside-down):
    (you can also see on the right some of the film that went out of the cap [​IMG]

    [​IMG]

    I also get a strange behavior: when I don't press the pedal for a minute or so, the entire electricity in my house gets shortened!

    btw, I read somewhere that you can throw off this cap, is this true?
     
  10. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    I think the capacitor is used to reduce pulses on the mains supply.
    Leaving it out will lead to noise.
    This noise can be heard on the radio and probably seen on TV as stripes.
    You can replace the capacitor with an 0.1 μF 250 Volts AC X1 or X2 capacitor.

    Greetings,
    Bertus
     
  11. radiohead

    Active Member

    May 28, 2009
    474
    31
    I personally don't see the difference in type of capacitor as long as it's rated at .1uF at 250V or above. It's used as a filter, not part of an RF circuit where stability would be an issue. Why wouldn't you be able to use a ceramic disk, tantalum, silver mica, polyester, or other capacitor rated at 250V or above?
     
  12. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
  13. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    From some reading I guess this is a safety capacitor that is designed to break upon failure.

    http://www.justradios.com/safetytips.html

    "Class X capacitors are used in “across-the-line” applications where their failure would not lead to electric shock. Class X safety caps are used between the “live” wires carrying the incoming AC current. In this position, a capacitor failure should not cause any electrical shock hazards, rather, a capacitor failure “between-the-lines” would usually cause a fuse or circuit breaker to open."

    The white plastic caps on both leads (one has popped out, btw) suggest that this is such kind of cap and needs to be replaced with an X2 safety cap.

    what do you think?
     
  14. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    I think a X2 will work fine.

    Greetings,
    Bertus
     
  15. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    Thanks bertus,

    I forgot to mention that the metal body of the cap was connected to the ground. I see that nowadays safety caps don't have a ground lead.

    Is this still ok?
     
  16. bertus

    Administrator

    Apr 5, 2008
    15,645
    2,344
    Hello,

    There are special Y capacitors with 3 leads.
    2 for the voltage connections and 1 for ground.

    Greetings,
    Bertus
     
  17. radiohead

    Active Member

    May 28, 2009
    474
    31
    Can you contact Brother's service center and get a factory replacement part?
     
  18. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    Last edited: May 30, 2009
  19. sitran12

    Thread Starter Member

    May 29, 2009
    13
    0
    Ok I made a rough schematics of the entire layout. The foot pedal acts as some kind of rheostat for the motor (at its max it just shorts the line).
    Can anyone tell me what kind of cap is this? X or Y, 2 or 3 leaded? I'm pretty sure its a safety capacitor because one side of the insulation has popped out

    thanks,

    [​IMG]
     
  20. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    It looks like an axial tantalum capacitor to me. I would recommend that you use a tantalum instead of an electrolytic because they have better performance.
     
Loading...