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Old 11th Aug 2020, 8:14 am   #1
Wishiknewmore
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Default RIFA again, 3 connector one Sewing Machine

I have just been asked to look at my sisters Husqvana Viking 6370 sewing machine, it suddenly started to run at full speed, ah, I know how to fix this I thought, shorted caps in the foot pedal…opened up pedal...no caps!, moved on inside the machine and found split Rifa across the terminals from the foot pedal, but I also found another cap mounted on the motor, a three terminal one (also split) connected to both motor terminals and to the motor casing.

Questions, are the caps only for RF suppression? Or do the reduce commutator arcing as well?

I am aware that I need X2 type caps across the supply and Y type between supply and ground, so how would I replace the three terminal one?

What is considered the best thing to do ?

Many thanks Philip
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Old 11th Aug 2020, 10:02 am   #2
Wishiknewmore
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Default Re: RIFA again, 3 connector one Sewing Machine

Whoops, wrong section
Mods please move
Philip
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Old 11th Aug 2020, 10:40 am   #3
turretslug
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Default Re: RIFA again, 3 connector one Sewing Machine

The three terminal ones are often referred to as "delta" types, from the supposed resemblance to the triangular circuit disposition between L, N and E connections- that might help with searching. I'm sure folk quite often just snip faulty ones out and leave it at that but it's probably best to replace them for the sake of the brushes and contacts as you say. Brush motors can be very antisocial otherwise, even clobbering supposedly robust services like digital radio and TV.

The syndrome of sewing machines going full pelt with a faulty RIFA has been mentioned a few times here, it means that there's quite a serious personal safety question to add to the charge sheet apart from the annoyance, smell, fuse-blowing and possible fire hazard.

Colin
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Old 11th Aug 2020, 4:22 pm   #4
Wishiknewmore
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Default Re: RIFA again, 3 connector one Sewing Machine

Thanks Colin
Thanks for the suggestion I have now found replacements at RS, I think I will refit as close as possible to the original, its always a bit different when its not your own!
I just have to think of what over bits to cover the min order size for free delivery
Philip
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Old 11th Aug 2020, 4:45 pm   #5
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Default Re: RIFA again, 3 connector one Sewing Machine

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I just have to think of what over bits to cover the min order size for free delivery
Some yellow 100nF capacitors.
 
Old 11th Aug 2020, 5:59 pm   #6
paulsherwin
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Default Re: RIFA again, 3 connector one Sewing Machine

I'm pretty sure the 3 terminal ones are just 2 class Ys in a single package.
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