Need help! Identify a capacitor

Thread Starter

sitran12

Joined May 29, 2009
13
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):


thanks!!
 
Last edited:

Wendy

Joined Mar 24, 2008
21,840
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



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

radiohead

Joined May 28, 2009
505
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.
 

Thread Starter

sitran12

Joined May 29, 2009
13
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
 

Thread Starter

sitran12

Joined May 29, 2009
13
By the way, is there a difference between an AC capacitor and a DC capacitor?
 

Wendy

Joined Mar 24, 2008
21,840
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).
 

R!f@@

Joined Apr 2, 2009
9,647
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.
 

bertus

Joined Apr 5, 2008
19,952
Hello,

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

Capacitors which have been designed to withstand the stresses and to comply with the appropriate standards are divided into three main categories: Class X1 These are for connection between live and neutral in situations where pulses of over 1.2kV can be expected. Class X2 These are for connection between live and neutral where transients will not exceed 1.2kV. Class Y These are made to the highest standard of all and are used for connection between a power line and earth or any other situation where failure might expose someone to a lethal shock. Most capacitors for mains use have the rather magical sounding property of self-healing.
Greetings,
Bertus
 

Thread Starter

sitran12

Joined May 29, 2009
13
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




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?
 

bertus

Joined Apr 5, 2008
19,952
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
 

radiohead

Joined May 28, 2009
505
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?
 

Thread Starter

sitran12

Joined May 29, 2009
13
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?
 

Thread Starter

sitran12

Joined May 29, 2009
13
Thanks bertus,

Hello,

I think a X2 will work fine.

Greetings,
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?
 

bertus

Joined Apr 5, 2008
19,952
Hello,

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

Greetings,
Bertus
 

Thread Starter

sitran12

Joined May 29, 2009
13
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,

 

ELECTRONERD

Joined May 26, 2009
1,146
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.
 
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