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6th Apr 2020, 3:53 pm | #1 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,383
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Another Rifa Smoke Bomb
A plea for help was received from SWMBO. The electric sewing machine is running without the foot switch being depressed, and it's smoking. Opening it up revealed a Rifa suppressor capacitor across the switch contacts that had decided to become a smoke bomb. The last one that did that was on the mains switch of the Quad 22 control unit. Nasty little blighters - change on sight. A new Class X 0.1uF and we're back in business. Hopefully the new cap will last longer than the brownie points......
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6th Apr 2020, 5:08 pm | #2 |
Octode
Join Date: Jan 2007
Location: Dorridge, West Midlands, UK.
Posts: 1,479
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Re: Another Rifa Smoke Bomb
My wife had just the same on her Viking machine, she was impressed I could diagnose it from the smoke and the smell.
Easy fix once you can get to it. Only thing you can say is wherever they crop up there will be problems, I always use the Panasonic ones to replace them and as yet have had no problems, whereas the Rifas were failing in my stock drawer before I could fit them!
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Chris Wood BVWS Member |
6th Apr 2020, 5:46 pm | #3 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,936
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Re: Another Rifa Smoke Bomb
It's not only Rifas. This is quite a common fault on electric sewing machines of all ages. The mains suppression caps fail short circuit across the switches or pedal rheostat, and you come home to find the machine happily sewing away on its own. It does remind you to unplug it from the mains when not in use
Of course, X2 caps aren't supposed to fail short circuit... |
6th Apr 2020, 6:33 pm | #4 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Another Rifa Smoke Bomb
Presumably if they're across the switch rather than the mains, the current limit imposed by the motor limits the grunt available to blow the little sod to smithereens
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6th Apr 2020, 6:38 pm | #5 |
Nonode
Join Date: Aug 2015
Location: Cambridge, Cambs. UK.
Posts: 2,198
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Re: Another Rifa Smoke Bomb
The RIFAs that are directly across the mains are easier. They self-destruct completely and need no further attention!
Martin
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BVWS Member |
6th Apr 2020, 9:00 pm | #6 | |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,553
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Re: Another Rifa Smoke Bomb
Quote:
Then the appliance continues to be used with the aftermath remaining inside it. |
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7th Apr 2020, 2:58 pm | #7 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,163
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Re: Another Rifa Smoke Bomb
You could probably improve the design by adding a Varistor across the mains and a snubber circuit across the motor.
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