Capacitor headache :-/

[rose-e-cheeks]

Hello all,

I've got a 1956 Bernina sewing machine that, after DAYS of restoring/cleaning/oiling, decided to blow its motor capacitor. It was a wax capacitor and I'd like to replace it with a modern equivalent. All the local electrical services are baffled, one did find a 0.1uF filter capacitor but it was way too big as the capacitor needs to be small enough to fit in the motor housing at the back of the machine.

The capacitor has the following printed on it -

0.1uF + 2 x 2500pF
250V 0 degree bis + 80 degrees c
284644 A 59.7
to -1.58 mHz7

Any help on tracking down a modern equivalent would be very much appreciated.

Many thanks,

Kat

 

[tazz]

Most electronic outlets such as RS Components, Farnell or As I have just found Rapid Electronics.
Electronic Components/Capacitors/Motor Run Capacitors | Rapid Online
Hope this helps

 

[rose-e-cheeks]

Thank you Tazz, you've been a great help.
Please could you tell me would a 1uF capacitor do the job safely?
Thanks ---

 

[guest119]

Careful Rosy, Tazz will be round next time he rips his flares :coolgleamA:

Boydy

 

[Barry White]

contact these guys I am sure they will help

Foot Control Capacitor - Sewing Machine Sales

just contact them and they will let you know if it will fit (fits in controler or motor depending on machine)

 

[Marvo]

That might be a 'two in one' type capacitor. How many wires were connected to it Kat? Can you show a photo of the connections on the end of the capacitor and the wiring that was connected to it please? Also was it the only capacitor connected to the motor or is there another one as well?

 

[rose-e-cheeks]

Thank you all for your help, I'm so glad to hear that I can find a new part for the job! Here's some more pictures of the machine motor and the connections.

Boydy -I've repaired some beauties in my time so a tear in a flare is no problem ;-)

xx

 

[Lucien Nunes]

The original part is a 'delta capacitor' i.e. three capacitors in one, connected in a triangle. 0.1µF between the leads, and 2.5nF from each lead to the case which is electrically connected to the frame of the motor by the mounting screw. It isn't a motor start or run capacitor but a radio & TV interference suppressor, so the motor will work without it but might blot out all radio/TV/WiFi etc in the neighborhood.

Depending on the motor insulation in your particular machine, the delta cap might be a safety-critical part and any capacitors used to replace it would need to be of suitable type, normally 'X2' rated for the large cap between the leads (which sees mains voltage but not to an exposed conductive part) and 'Y' rated for the two small caps to the case (failure of which could make an exposed part live). However it should be possible to source a direct replacement delta cap as they are still used, which will normally have suitably X & Y rated caps inside.

The cap in the following link has the correct values and safety approvals but instead of a metal case a third lead is used to connect to the motor frame. You can probably find a better fit for your situation with a bit of searching of RS/CPC/Farnell etc.

http://uk.rs-online.com/web/p/paper-capacitors/1215449/

FWIW if you don't already know the date of the sewing machine, your existing delta cap is dated July 1959.

 

[Knobhead]

It’s a universal motor. As Lucian has said the capacitor is for RF suppression.

The motor should run OK without it but make sure you listen to Radio 1, you’ll not notice the high pitched whine.

To be honest I’m surprised a sewing machine has one fitted.

 

[rose-e-cheeks]

Thank you all so much!
If the machine can run without it how come it blew? It tripped my electric box when it went and made a pretty blue spark and a puff of smoke. I'll put a new fuse in the plug and give the old gal a go, failing that the link Lucien provided will be of much use. I'm a radio 2 listener so a high pitched whine won't be welcome :-D

Thanks once again,

Kat
---

 

[Lucien Nunes]

Capacitors usually fail short-circuit, and because this one is across the mains it would have dissipated a large amount of energy prior to the MCB/RCD reacting. This is actually quite a common fault on old equipment, not just motors, and I have seen many good pieces of kit discarded or abandoned for no reason other than the fireworks of the suppressor going pop giving the false impression of a catastrophic failure.

You would need to make safe the ends of the leads before testing without the cap. Please fit the replacement - universal motors produce really annoying interference that could affect your neighbours as well as yourself. Do ensure the replacement is suitable for the purpose - it is not sufficient to fit non-safety-approved caps of the correct capacitance and voltage - and correctly installed w.r.t. isolation from the metalwork.

 

[DPG]

The original part is a 'delta capacitor' i.e. three capacitors in one, connected in a triangle. 0.1µF between the leads, and 2.5nF from each lead to the case which is electrically connected to the frame of the motor by the mounting screw. It isn't a motor start or run capacitor but a radio & TV interference suppressor, so the motor will work without it but might blot out all radio/TV/WiFi etc in the neighborhood.

Depending on the motor insulation in your particular machine, the delta cap might be a safety-critical part and any capacitors used to replace it would need to be of suitable type, normally 'X2' rated for the large cap between the leads (which sees mains voltage but not to an exposed conductive part) and 'Y' rated for the two small caps to the case (failure of which could make an exposed part live). However it should be possible to source a direct replacement delta cap as they are still used, which will normally have suitably X & Y rated caps inside.

The cap in the following link has the correct values and safety approvals but instead of a metal case a third lead is used to connect to the motor frame. You can probably find a better fit for your situation with a bit of searching of RS/CPC/Farnell etc.

http://uk.rs-online.com/web/p/paper-capacitors/1215449/

FWIW if you don't already know the date of the sewing machine, your existing delta cap is dated July 1959.

Definately wise advice there about class X and Y ratings of caps. A lot of people aren't aware of these and just match voltage and capacitance value. Daz

 

[rose-e-cheeks]

Hello again,
I'm happy to report that my lovely old gal is up and running again with no capacitor AND no interference with TV or radio
Thanks to everyone that helped me with this and I wish you all the best for the future.
Kat
---
P.S. I've just collected another vintage sewing machine that smokes from the motor after a few seconds use so I may be back lol!

 

[telectrix]

must be an old motor. phony blair banned smoking in 2008.:ack2:

 

[guest119]

Hello again,
I'm happy to report that my lovely old gal is up and running again with no capacitor AND no interference with TV or radio
Thanks to everyone that helped me with this and I wish you all the best for the future.
Kat
---






P.S. I've just collected another vintage sewing machine that smokes from the motor after a few seconds use so I may be back lol!

Is it the correct voltage for the UK?

Boydy

 

[Lucien Nunes]

AND no interference with TV or radio

Did you check with all nearby radio amateurs? Did you listen at both ends of long wave? Manufacturers did not spend ££ on fitting unnecessary parts! Admittedly there's less AM in use today and that is the worst affected.

As for the smoking motor, that's not good. Did you see where the smoke came from? Examine the commutator all the way round, identify any odd (burnt, discoloured, damaged) copper bars and post a picture. Many brush motor faults leave recognisable damage signatures on the comm. Are the brushes intact?

 

[DPG]

I don't think she's going to know what a commutator is Lucien Daz

 

[Lucien Nunes]

But a 2 second Google will solve that, now I've given it a name.

 

[Knobhead]

Lucien, have you ever sat and talked to a ham radio enthusiast when there’s no escape? I worked with one!

Rose, keep using the sewing machine as a service to the human race.

 

[Lucien Nunes]

How do you know I'm not one? FWIW I am licenced to operate certain kinds of R/Ts but with a purpose in view, not just for kicks. Either way, clean reception is best!

 

[rose-e-cheeks]

Yes Boydy the new old machine is made for the UK
I've taken the motor off and it looks to be full of sewing machine oil, perhaps the reason for the smoking? Over oiling? It smokes more or less immediately when used. I haven't had enough time to have a proper look yet.

Lucien - there is genuinely no interference. I live in the middle of nowhere and only have two neighbours - we did a test and nothing happened to their tv or radio either. I can't explain it either but I'm not going to question it!

Thanks all

Kat
---

 

[Besoeker]

Capacitors usually fail short-circuit, and because this one is across the mains it would have dissipated a large amount of energy prior to the MCB/RCD reacting. This is actually quite a common fault on old equipment, not just motors, and I have seen many good pieces of kit discarded or abandoned for no reason other than the fireworks of the suppressor going pop giving the false impression of a catastrophic failure.

You would need to make safe the ends of the leads before testing without the cap. Please fit the replacement - universal motors produce really annoying interference that could affect your neighbours as well as yourself. Do ensure the replacement is suitable for the purpose - it is not sufficient to fit non-safety-approved caps of the correct capacitance and voltage - and correctly installed w.r.t. isolation from the metalwork.

Excellent post if I may say so.
You may already know that my background is in power electronics/variable speed drives and has been for decades.
As far back as predating IGBTs for inverter power circuits. We built them from component level using fast thyristors with forced commutation circuits. These were resonant LC circuits often with peak currents of a few thousand amps. You need the right capacitor for that application - getting it wrong isn't an option.

Just a bit of my background..... so back on to the sewing machine theme.
A while ago my wife bought an old Singer electric sewing machine on ebay, possibly about the same vintage as that of the OP.
We collected from the previous owner and noted that the wiring was in an absolutely parlous state.
As we were leaving with it loaded into my car, the parting owner had some parting words of profound wisdom.

"I think you just might need an electrical person to check that out before you use it."
My wife, completely dead pan, looked him in the eye.
"I think I just might know where to find one."