Need help! Identify an AC capacitor

[sitran12]

Hi all,

Sorry if this slightly off the mobo-caps topic .
I need help identifying a strange capacitor (not a MOBO cap but an AC cap) 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!!

[Toasty]

Re: Need help! Identify an AC capacitor

Where in the machine is it connected. Close-ups are good for ID but lousy for locating the item. How is it connected to the machine? Across the mains or from mains to chassis?

It's likely a noise suppression X or Y cap, depending on how it's connected.

>>with a foot suppressor (AC)<<
Do you mean a speed control?

Toast

[sitran12]

Re: Need help! Identify an AC capacitor

yes, I meant the speed control (foot control).
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?

[Toasty]

Re: Need help! Identify an AC capacitor

I don't know if that can be removed without causing damage to either the speed control or the connected machine. The motor may depend on the cap being there.

I would take it to a Vacuum & Sewing Machine appliance repair shop and see if they have a similar part they can sell you.

You do want one that has the insulated wire leads coming out of it, like this one has.

You don't want one that is meant to be soldered into a circuit board with bare thin leads; such as the other forum you posted in showed you from Radio Shack.

Toast

[sitran12]

Re: Need help! Identify an AC capacitor

Thanks, I was shooting in all directions

I figured that the circuit board capacitor was too good to be true
I don't think I have a chance at the repair shops around here - they'll rip me off or tell me to replace the entire pedal.

Do I really need this exact kind (with insulated wire leads)? any special reason besides the current?

I'm trying to avoid spending big $$$'s

thanks,

[Toasty]

Re: Need help! Identify an AC capacitor

Model # of machine and pedal please. I'll check locally and see. I've several shops nearby that I deal with.

Toast

[sitran12]

Re: Need help! Identify an AC capacitor

I appreciate it, but I don't suspect you ship overseas

anyway, it's a very old Brother Mademoiselle, it looks like this:


There isn't any model # on the machine or pedal, but from the manual I found on the net it is most likely a 606. But can be any of the models 461 761 606 607.

Any help or advice will be greatly appreciated!

[sitran12]

Re: Need help! Identify an AC capacitor

Btw, Toasty, I did some reading and I think I understand what you meant - this is a safety capacitor, right?

I'm cross-posting this also on http://forum.allaboutcircuits.com/sh...0&postcount=13,

happy day

[kc8adu]

Re: Need help! Identify an AC capacitor

better pics of the foot control will help.
its likely there to suppress noise and a film cap will do fine.
as for lead insulation spaghetti or heatshrink works.it doesnt care if its on a pc board or not.

[sitran12]

Re: Need help! Identify an AC capacitor

thanks,

I posted a rough schematic of the layout:


There's also a picture of the pedal:
(you can also see on the right some of the film that went out of the cap)

http://img30.*************/img30/8871/280520091062.jpg

The metal case was also grounded, so I'm not sure if this is an X or Y cap..

will appreciate the help

[sitran12]

Re: Need help! Identify an AC capacitor (better pics)

better pics:

pedal:


capacitor (with right cap popped out):
you can see the grounding too

[Toasty]

Re: Need help! Identify an AC capacitor

Is this a 3 lead cap? Your pictures are not showing what really needs to be seen. Get the black tape off and pull it up so all the wiring to it can be seen please. Your drawing suggests that this is an interference/safety combination cap of some type.

You reported that it shorts out the power. That would mean that it is indeed grounded thru its case.

The schematic you drew may be misleading.Without an actual working unit, there is no way to know whether this is:
(a) 2 caps in series across the speed control element and with their common connection to ground.
(b) a bypass unit that passes current through itself and has the capacitor connected to the through line and its case which is then connected to ground.

If it is (b), then you'll need the original item to fix it. It needs to be able to pass the full current plus, that the machine draws.

There are solutions to both types, but I am hesitant to suggest anything further as they posses both electrical and fire hazards. It's a situation where "If it were mine, I'd do this", because I'm confident of my abilities and I'm risking my property.

So, in conclusion, I would recommend that you either buy the correct component or buy a new controller.

Toast

[sitran12]

Re: Need help! Identify an AC capacitor

Thanks Toast. You helped me a lot (I'm quite educated on safety caps by now ).

anyway, I added the pics above. I think it's (b). You can see the capacitor connected in parallel to the line.
The current flows from the brown to the blue (through the 'rheostat-like' pedal) and then into the motor and back to the blue of the mains (so the blue in the pedal is actually the line and not the neutral, I believe).

[Toasty]

Re: Need help! Identify an AC capacitor

I'd worked on my comment so long I didn't see your picture post. TY

I'll suggest now:

2 - Y style caps of matching or better voltage and capacitance. One leg of each to ground, the other leg to the 2 terminals where the bad one is connected now.

See attached.

Toast

PS: The controller is actually a series resistor. Typically a "carbon pile" type. As the pressure on the pedal is increased, the carbon discs inside are pressed more firmly together and the resistance drops, making the motor run faster.

[sitran12]

Re: Need help! Identify an AC capacitor

Thanks! you made my day!
So that single capacitor served as 2 Y-style capacitors?

Just for my education - I think I saw some combined XY caps with 3 leads. would they fit too?

btw, would you mind if I share your response and schematic with the guys at http://forum.allaboutcircuits.com/sh...d.php?p=146838 ?

[Toasty]

Re: Need help! Identify an AC capacitor

No. Must be 2 Y caps. Y caps, if they fail, are engineered to fail "open" and thereby not cause an electrocution hazard.

Okay to share.

Toast

[japlytic]

Re: Need help! Identify an AC capacitor

This capacitor would be an X2 (or X1) class unit.

I have seen "box" capacitors with one X2-class and two Y-class units in them, but it is highly unlikely that a tubular capacitor with one X2-class and two Y-class units exists.
The largest Y-class unit I have seen is 0.01uF.

[sitran12]

Re: Need help! Identify an AC capacitor

No offense guys, but I'm still confused: 2 senior members tell me that I need either X or Y.
also, this guy identified exactly the kind of pedal and circuit I had (right down to the carbon discs) but I didn't understand too much of his recommendation:
http://forum.allaboutcircuits.com/sh...9&postcount=28

Q1: what about the metal bracket, isn't it used for grounding of some sort?

Q2: can I damage anything if I use an X2 cap and add 2 Y caps just to be safe?

please advise, still

[Toasty]

Re: Need help! Identify an AC capacitor

>>This capacitor would be an X2 (or X1) class unit.<<
Incorrect. Your information is going to get someone killed or injured.

It is NOT a X cap.

Please read what I posted before. If you use an X cap and it FAILS, the metal frame/housing may become energized and pose an electrocution hazard.

X caps are used ACROSS the mains. X capacitors may NOT be used from mains to ground or casing.

Y caps are used FROM mains to frame/ground. Y capacitors can also be used as an X-style cap across the mains. They are engineered to fail OPEN.

Rated impulse voltages:
X1 - 4kV X2 - 2.5kV

Y1 - 8kV Y2 - 4Kv

Two(2) Y2 types are what you should use here, as I described.

Toast

[sitran12]

Re: Need help! Identify an AC capacitor

Thanks Toast, I'll stick to the safe side and follow your advice.

I'll post the results once it's done (unless I get myself fried )