Sewing machine query - capacitor requirements

[Mrs Twosheds]

Hi guys. Any advice greatly appreciated, please.

I have a 1970 Bernina sewing machine. It works a treat, but has just popped loudly and emitted a puff of smoke. I gather that the motor suppressor/capacitor gives up the ghost on these old machines as a regular thing. Sadly, Bernina don’t make the part any longer. Opinion seems to be divided as to whether to carry on using it without this part, or whether it’s unsafe/potentially damaging to the machine. There are supposed ‘replacement’ parts on eBay, but these have only 2 wires and the original has 4 (a double unit?).

I’ve found mention of the part, which claims it requires: 1x0.02 uFx2. 1x0.06 uFx2. 2x 2000 pF Y2. 1x2.2M (followed by a symbol resembling a horseshoe). I have no idea what this means. Can it be substituted with anything else I can buy? Is it safe to use?
Huge thanks so much for any help you can offer.

 

[mainline]

Hi guys. Any advice greatly appreciated, please.

I have a 1970 Bernina sewing machine. It works a treat, but has just popped loudly and emitted a puff of smoke. I gather that the motor suppressor/capacitor gives up the ghost on these old machines as a regular thing. Sadly, Bernina don’t make the part any longer. Opinion seems to be divided as to whether to carry on using it without this part, or whether it’s unsafe/potentially damaging to the machine. There are supposed ‘replacement’ parts on eBay, but these have only 2 wires and the original has 4 (a double unit?).

I’ve found mention of the part, which claims it requires: 1x0.02 uFx2. 1x0.06 uFx2. 2x 2000 pF Y2. 1x2.2M (followed by a symbol resembling a horseshoe). I have no idea what this means. Can it be substituted with anything else I can buy? Is it safe to use?
Huge thanks so much for any help you can offer.

The horse shoe will = ohms

It sounds like it’s a bit more than just a capacitor it’s more than likely to have resistors in series with capacitors for suppression.

 

[Mrs Twosheds]

The horse shoe will = ohms

It sounds like it’s a bit more than just a capacitor it’s more than likely to have resistors in series with capacitors for suppression.

Ahh…..right. Thank you. It’s still working perfectly, but online sewing forums seem uncertain as to whether it’s safe to use.

Some sewing machine repair gurus are a bit gung-ho and suggest it won’t do any harm, but others say it’s there for a reason and shouldn’t be operated without it. Presumably, it won’t be easy to find substitute suppressor/capacitors with the same properties? Is there any hope?

 

[DPG]

Ahh…..right. Thank you. It’s still working perfectly, but online sewing forums seem uncertain as to whether it’s safe to use.

Some sewing machine repair gurus are a bit gung-ho and suggest it won’t do any harm, but others say it’s there for a reason and shouldn’t be operated without it. Presumably, it won’t be easy to find substitute suppressor/capacitors with the same properties? Is there any hope?

I would try and get a replacement. Better than risking it injecting noise or transients on to your mains wiring.

 

[Mrs Twosheds]

I would try and get a replacement. Better than risking it injecting noise or transients on to your mains wiring.

Thank you, DPG. I will certainly do that if I can. I can find every kind of capacitor online but this type - I’m reluctant to buy a secondhand one, as it’s probably the same age and will presumably succumb to the same fate. I’ll continue to search. I notice that someone in Norway makes a 3D version of it, but I’m not sure whether that’s likely to work

Huge thanks again, guys.

 

[DPG]

Thank you, DPG. I will certainly do that if I can. I can find every kind of capacitor online but this type - I’m reluctant to buy a secondhand one, as it’s probably the same age and will presumably succumb to the same fate. I’ll continue to search. I notice that someone in Norway makes a 3D version of it, but I’m not sure whether that’s likely to work

Huge thanks again, guys.

Post a photo on here if you can

 

[mainline]

You could throw it away and replace it with a decent mains filter

 

[DPG]

You could throw it away and replace it with a decent mains filter

Good idea that. Keeps things simple.

 

[Avo Mk8]

Thank you, DPG. I will certainly do that if I can. I can find every kind of capacitor online but this type - I’m reluctant to buy a secondhand one, as it’s probably the same age and will presumably succumb to the same fate. I’ll continue to search. I notice that someone in Norway makes a 3D version of it, but I’m not sure whether that’s likely to work

Huge thanks again, guys.

There is a thread on a Vintage Radio forum that discusses this suppressor capacitor, shows a circuit diagram, gives someone's sketch of where the wires go, and a link to a further thread. There are some suggestions of suitable replacement components.

Bernina Sewing Machine Capacitors - UK Vintage Radio Repair and Restoration Discussion Forum

Bernina Sewing Machine Capacitors Other Vintage Household Electrical or Electromechanical Items

www.vintage-radio.net

Also

View: https://youtu.be/2MiqhoIjPQg?si=RqAgZJG8cND9tCsk


Your sewing machine will work without it, but doing that might cause electrical interference to radio's TV's etc. and other households around. Also if the sewing machine motor is a traditional commutator type, with carbon brushes (Edit - which I now see it is!), the interference suppressor might normally help reduce arcing, and hence wear, on the commutator/motor brushes. But you could operate the machine, at least in the short term, without the suppressor, until someone complains

Possible replacement one of these? (Capacitor values not particularly critical)

https://files.kempstoncontrols.com/files/12bdab79b5e15277f870e677013a42d0/511-330A.pdf

 

[Mrs Twosheds]

Oh, wow, guys! Thank you so much for all of this - was worrying that I might have to abort sewing projects, but I have new hope. I shall work my way through your excellent suggestions (preferably without upsetting the neighbours ). It’s a really beautiful piece of engineering and it would be such a shame not to use it. On my way across to the Bernina discussion group now

 

[DPG]

Oh, wow, guys! Thank you so much for all of this - was worrying that I might have to abort sewing projects, but I have new hope. I shall work my way through your excellent suggestions (preferably without upsetting the neighbours ). It’s a really beautiful piece of engineering and it would be such a shame not to use it. On my way across to the Bernina discussion group now

Let us know how you get on. And whether you are related to Arthur two-sheds Jackson.

 

[Mrs Twosheds]

Sadly not, but roughly the same vintage! I’ll keep you posted as to my progress (my dear old dad was an electrical engineer - I wish I’d paid more attention).

 

[Marvo]

I would replace it with a noise filter board you can scavenge from an old microwave or washing machine. If you're not in a scavenging mood they're also available as new items from Amazon or EBay although I'd strongly recommend buying an OEM version and not a cheap Chinese knockoff. It will arrive as a bare PCB so obviously you'd need to put it into a small profect box. They look something like this;

 

[mainline]

I would replace it with a noise filter board you can scavenge from an old microwave or washing machine. If you're not in a scavenging mood they're also available as new items from Amazon or EBay although I'd strongly recommend buying an OEM version and not a cheap Chinese knockoff. It will arrive as a bare PCB so obviously you'd need to put it into a small profect box. They look something like this;

View attachment 116750

I doubt what you're suggesting would be very safe or aesthetic.

 

[Mrs Twosheds]

I would replace it with a noise filter board you can scavenge from an old microwave or washing machine. If you're not in a scavenging mood they're also available as new items from Amazon or EBay although I'd strongly recommend buying an OEM version and not a cheap Chinese knockoff. It will arrive as a bare PCB so obviously you'd need to put it into a small profect box. They look something like this;

View attachment 116750

 

[Mrs Twosheds]

Thank you so much, Marvo. That’s a really interesting idea - I’ll look into that, too!

 

[Avo Mk8]

I would replace it with a noise filter board you can scavenge from an old microwave or washing machine. If you're not in a scavenging mood they're also available as new items from Amazon or EBay although I'd strongly recommend buying an OEM version and not a cheap Chinese knockoff. It will arrive as a bare PCB so obviously you'd need to put it into a small profect box. They look something like this;

View attachment 116750

I honestly think this is not a practical way to go.
There's no wiring or access to power in the body of the sewing machine, it's all in the (separate) motor housing as far as I'm aware, and there is very limited space. Given you can buy an encapsulated X & Y capacitor/resistor module of the right type that would drop in, the delta filter I linked to would be a much easier fix.
Also the example you show doesn't seem to have the capacitors needed to quench the arcing of the brushes of the motor, so probably wouldn't do the job!

Just to illustrate the space available, this is where the suppressor needs to go (or equivalent for the machine in question)

 

[Marvo]

Yeah, the safety and aesthetics would need to be assessed by the person installing it and my suggestion may not be a practical solution depending on the layout of the existing setup. Looking at the component values in the first post I summized it to be noise suppression filter rather than a brush arc suppression snubber but I could of course be wrong. With old brush motors most of the brush arc suppression was mitigated by the brujshes being resistive and they were notorious for developing excessive arcing when generic replacement brushes were fitted which often were of the same form factor but a different resistance to the OEM brushes. Brush motors of that era used to generate large amounts of noise that was especially unwanted because the medium wave radios in everyones kitchen andv lounge were very prone to picking it up. The components listed look to me like noise suppression and the generic filter board I suggested should suffice on a technical level for that purpose although maybe not on a logistical one.