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Is this a three leg capacitor?

galeap

New Member
Hello all,

This is my first post so here so I'll see how I go.

I am after some details on a component that has failed in my wife's sewing machine. The machine is a Pfaff 1222. From what I can still read on the out case, the component has the following markings:
ERO 6F
F1740-410-307
0.1uF X
+2x2500pFY
250V
560-7HPF
-25/+85C
fo=1.6MHz
25/085/21

I have googled the various part like numbers and found nothing exact however I have found a site with the first part of the F1740 code that had data sheets for suppression capacitors. Is this what this item is?

Does anyone know if this part is still available? If not can I make up an equivalent out of individual no polarised power capacitors of similar values?

Pics included to help identify.



http://i107.photobucket.com/albums/m312/galeap/FailedComponent4.jpg


All help is appreciated.

Thanks,

Pete.
 

JimB

Super Moderator
Most Helpful Member
Yes it is a three legged capacitor, in fact it is 3 capacitors in one package intended for EMI suppression.

There is a 0.1uF "X" capacitor, which will connect across the mains supply, and two 2500pF "Y" capacitors which connect from line and neutral to earth.

Looks like the poor thing has committed suicide!

JimB
 

Hero999

Banned
I've seen capacitors like that many times before, they're pretty common on appliances with a universal motor. I wouldn't be able tell you where to buy one from though. I suggest you go to your local tip and pick up an old vacuum cleaner which is bound to have one.
 

galeap

New Member
Thanks guys for the quick replies.

So am I correct in thinking that if I can't source another one of these three in one capacitors, I can build one up out of three separate capacitors of similar size?

I assume that the capacitors are not electrolytic. So I was thinking of using the following:
.1uF Cap Mains Sup 275V DX2 0.1 uF (R2628) - Dick Smith Electronics - Australia.

And for the 2500pF, the closest that Dick Smith has is 3300pF. Cap Cer 3kV Z5U 10mm LS.0033uF (R2393) - Dick Smith Electronics - Australia.

Would this do, or should I try and get closer to the 2500pF mark by parelling up a few smaller caps?

Also, what does the fo = 1.6MHz on the failed unit mean? Does it have something to do with filtering frequency or oscillation frequency? Curious.

Thanks again.

Pete
 

audioguru

Well-Known Member
Most Helpful Member
The parts look extremely old.
Carbon composition resistors with a 10% tolerance have not been used for 50 or 60 years.
A little transistor is in an old metal case.
 

Boncuk

New Member
You might replace the 0.1µF capacitor with a WIMA type MP 3-X2 100nF.

It is rated 275VAC according to DIN EN 132400 and IEC 60284/14/2 classes X2, Y2 and Y1 (pin distance 15mm, price 55Cent) for spike suppression.

Forget about the two 1500pF caps. There is no earth connected to the PCB.

If you can't find a suitable cap just omit them all. You might get some interference on the TV screen when operating the sewing machine.

The problem with those caps is the fact, that they are steadily connected to mains even if the motor is not running.

Boncuk
 

Boncuk

New Member
The parts look extremely old.

A little transistor is in an old metal case.
I looked for an OC71 transistor, but couldn't find one. It doesn't seem that old. :D
 

MrAl

Well-Known Member
Most Helpful Member
Hello,

That looks like an offline power supply of some kind.
I hate to say it, but if those caps blew there could be something else
wrong with the circuit too.
Maybe you can get a schematic.
 

Boncuk

New Member
Hello,

That looks like an offline power supply of some kind.
I hate to say it, but if those caps blew there could be something else
wrong with the circuit too.
Maybe you can get a schematic.
I'd not be worried about any other thing wrong. Those caps blow up after ten years without any other malufunction.
 

Hero999

Banned
Forget about the two 1500pF caps. There is no earth connected to the PCB.
The Y2 capacitors will be connected to the motor's metal frame so they are essential. The motor's metal might or might not be earthed. If the motor is inside a plastic enclosure and there are nylon gears or rubber belts in the drive chain if might not need to be earthed but should still be connected to the Y2 capacitors.
 

Boncuk

New Member
I guess in that particular case there is no connection to the motor housing.

There are two wires in and two wires out.
 

galeap

New Member
Hi everyone,

Thanks for the feedback to date on my problem.

A little more info to clear up a couple of items being discussed.
The sewing machine is approximately 30years old, its a Pfaff 1222 model and has been a little trooper over the years never missing a beat, well until now that is. As for the parts being 40+ years old, I don't know, maybe Mr Pfaff hasn't changed his design in a while at the time. When I opened it up and saw the full scale components I thought that this was going to be an easy fix, until I noticed the third leg on the capacitor.

I took the picture of the circuit board removed from the sewing machine, if you look closely there is nine pin lugs at the bottom of the circuit board that wiring attaches to. The only circuit diagram I have at the moment is what I found under the terminal box lid, and it only shows the wiring leaving this board via these pins. Not sure what the switch that pins 7,8 and 9 go to is, it may be something to do with making the machine go forward and reverse.



As for the wiring you see in the original photo, the blue wires go to the power plug which the sewing machines foot plugs into, and I believe these wires carry the speed signal (which I think is a simple resistance). While the two black wires are coming from the power switch (secondary side), the wiring between the power switch and plug (same one that the foot plugs into is not in the photo).

Finally, in the original photo there is a small glass fuse (2Amp) which I had removed before taking the shot, which as you would expect was well and truly blown.

The topic about earthing got me curious, sewing machine has a three pin power plug (i.e earthed) however this goes to the foot pedal which then has a four pin lug which attaches to the sewing machine. From what I can work out, two of these pins are for the power supply (240Vac Active/Neutral), with the remaining two used to carry the speed signal, which I believe is nothing more than a resistance from a potentiometer in the pedal. Which leaves me wondering how the sewing machine body which is steel is being earthed. The two coils in the centre of the board share a iron core so this is probably an isolation transformer. They seem so small for such a duty, would this make sense?

I have googled for a schematic diagram for the circuit board but have had no luck, and have not had time to reverse engineer one for it yet.

So, I'm still at a bit of a loss for what to do next. What is the public opinion on the necessity of the capacitors with this additional info? Particularly with regards to the fact that I can't identify a bonded earth to the machine.


Thanks heaps,

Peter.
 

Hero999

Banned
Where does the third capacitor leg connect to?
 

galeap

New Member
Hi Hero999,

One leg (Green/Yellow wire) seems to go to pin 9, while the second leg (black) goes to one the primary coil of what I believe is an isolation transformer, and the third leg (black) goes to the secondary coil as well as to a diode and to one of the two black box components in the centre of the board, markings BBC CS1 05do4 517A.

Not sure if the above description helps much.

Pete
 

Hero999

Banned
The coil looks like a filter rather than a transformer.

Where does pin 9 go? The wiring diagram in the picture you've posted doesn't say.
 

galeap

New Member
Hi Hero999,

Not entirely sure where pin 9 goes, the diagram on the lid looks like a switch, which I'm guessing is the lever switch on the sewing machine that causes a change of sewing direction from forwatd to reverse.

I will seeif I can work out what switch this is later on by opening up the sewing machine a little more.

Cheers,

Pete
 

galeap

New Member
Hello all,

I've had a look around the local electronic stores and can't locate the failed part.

So I have decided that I will make one up out of three separate capacitors of the nearest values I can find.

Am I correct in thinking that the wiring arrangement will be as follows to make the equivalent.
------------0.1uF
+--------------||--------+
|--------------||--------|
|--3300pF--- 3300pF-----|
|---||-----+---||--------|
|----------|-------------|
o----------o-------------o

All capacitors to be rated over 250V.
I assume that the outer two legs will be the black legs on the failed component and the centre one will be the green/yellow leg. Does this sound correct? Does anyone have a data sheet for the failed component that they could send through? I couldn't find anything on the net for any of the numbers stamped on the case.

I have attached another photo of the failed component that shows a three leg capacitor like symbol, in case this helps. Also, what is the meaning of Y=gn/ge ?



Thanks for any help on this.

Pete
 

Hero999

Banned
Yes the middle leg goes in-between the two 3300pF capacitors.

Don't use any old capacitors, for safety reasons the 100nF capacitor needs to be an X-rated capacitor (don't wory not a p0rno ;D, it's a resistance to over-voltage) and the 3300pF capacitors need to be Y-rated.

X-rated capacitors are classified as safe to be connected across the mains and Y-rated capacitors are classified as safe to be connected from mains to earth or an exposed metal surface. There's different ratings, X1, X2 and X3 and Y1, Y2 and Y2, I can't remember what they mean (use Google if you want to find out) but X2 and Y2 are standard ratings so go for them.
 

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