Shock from unplugged sewing machine lead

[sewing]

Two of us have had a shock from a lead that had been disconnected from a Singer sewing machine several hours earlier.
The machine is fairly new and not been heavily used.
The shock was definitely stronger than just static.

My concern particularly is that this is a machine being used with children.

Can someone tell me what is wrong with the lead or is this a normal residual charge for an appliance of this kind?
Thanks in advance for any advice.

 

[telectrix]

it's possible that the machine's power supply contains capacitors which charge up in use. after unplugging, they could still hold a charge. if you leave the machine plugged in after use with the socket still switched on, they may slowly discharge.

 

[westward10]

That shouldn't happen. I had a vacuum cleaner which did this and discovered the suppressor was incorrectly connected.

 

[freddo]

Mother has a hairdryer that did this, I ended up fitting a discharge resistor across the mains filter capacitor.

 

[telectrix]

i used to cut the filter capacitors out of TVs. back in the 70s, they always used to short out and explode, usually taking out the fuse.

 

[Lucien Nunes]

OP - your wording is a little ambiguous - please can you confirm that the shock is from the pins of the mains plug, when it has been unplugged from the wall socket but is still connected to the machine.

If so, then as stated above it is likely to be from an interference suppressor capacitor(s) that should bleed down after disconnection from the supply, but apparently are not doing so, possibly because of an open-circuit bleeder resistor. If it is fairly new, I would contact the manufacturer.

 

[sewing]

Thanks for your advice here -and some interesting thoughts.

The shocks happened with the lead detached from the sewing machine - and had not been used for some hours.
It was before inserting the socket (female) into the machine pins.
It was not connected to power yet.
The shock came from the machine socket part of the lead.

The lead comprises of a plug and a socket that inserts into the machine for combined with a lead that goes on the floor to operate a foot pedal. I think there may be a capacitor (?) in the pedal but I'm no expert.
I'll contact the manufacturer but curious as I have not encountered shocks outside of a live supply before - also I know nothing

 

[DPG]

I'd also go with the capacitor theory.

 

[Lucien Nunes]

There will be capacitors in the foot pedal speed control circuit that could hold enough charge to deliver a noticeable shock. What puzzles me is that it should not normally be possible to touch the contacts of a socket, which could be fully live if the lead were connected to the supply. From what part of the socket assembly did you get the shock?

 

[DPG]

Good point about the socket. It does seem strange to be able to touch the contacts.

 

[HappyHippyDad]

There will be capacitors in the foot pedal speed control circuit that could hold enough charge to deliver a noticeable shock. What puzzles me is that it should not normally be possible to touch the contacts of a socket, which could be fully live if the lead were connected to the supply. From what part of the socket assembly did you get the shock?

Good point about the socket. It does seem strange to be able to touch the contacts.

I think the OP will come back and say he meant to say 'plug' rather than 'socket'.

 

[sewing]

I'm probably incorrect with my terminology but the shock came from the black flange connector that plugs into the machine. The machine has a set of pins on one side and the connector plugs into these. The connector is female insofar as it has three (I think) holes to link with the machine. Thanks for thoughts.

 

[DPG]

I think the OP will come back and say he meant to say 'plug' rather than 'socket'.

But if it's the connector feeding the machine then it won't have touchable contacts.

 

[ruston]

Are you just pulling the connector plug out at the machine and leaving it plugged in and switched on at the mains?

Does it look like this?

 

[DPG]

Are you just pulling the connector plug out at the machine and leaving it plugged in and switched on at the mains?

Does it look like this?

They often have a bespoke connector rather than a standard IEC type.

 

[ruston]

They often have a bespoke connector rather than a standard IEC type.

I agree , but anything can happen...
Edit. I just used that as an example of an insulated connector.

 

[sewing]

Yes, it is a bespoke connector for the Singer machine but looks something like the one illustrated.
No, the power was not connected at all and had not been so for some hours.
And also I would agree that getting a shock from an insulated connector seems strange to me but we sure felt it on two separate occasions!
Appreciate the conversation, Thanks

 

[ipf]

Attaching a photo may well show more clearly what you are trying to explain.

 

[Lucien Nunes]

I think we're up to speed with the configuration, which is pretty normal for sewing machines. There is a cordset comprising the 13A plug, foot-pedal speed control and a custom connector to fit the sewing machine inlet. When the cordset is completely disconnected from both the machine and the mains, it is possible to get a shock from the female connector, due to charge stored in the speed control pedal. The only thing that is not clear is how the OP is touching the contacts of the connector.

Please could we have a pic of the connector showing, if possible, where you touched it to receive the shock. There have been cases of conductive plastic having been used in moulded electrical products, but not from reputable manufacturers.

 

[ipf]

I think we're up to speed with the configuration, which is pretty normal for sewing machines. There is a cordset comprising the 13A plug, foot-pedal speed control and a custom connector to fit the sewing machine inlet. When the cordset is completely disconnected from both the machine and the mains, it is possible to get a shock from the female connector, due to charge stored in the speed control pedal. The only thing that is not clear is how the OP is touching the contacts of the connector.

That's what I was hinting at. Not really interested in a photo of a sewing machine.