Suppression caps on sewing machine motors - needed? - UK Vintage Radio Repair and Restoration Discussion Forum

avocollector · 8th Apr 2021, 11:14 am

Got a nice metal bodied sewing machine electric motor 230v 5Amp 30 watt model (think it's Sew brand) to use with a minature lathe milling head (Emco Unimat 3 part) I have. Connected it all up to the mains for a tryout and everything was fine except one of the mains suppression caps went bang with a vengence - ruptured and brown goo everywhere.

How essential are these to supress rf

Tempted to not bother replacing it as the motor will be only used in my shed and on a isolating transformer supply.

Sideband · 8th Apr 2021, 12:49 pm

They might also help reducing brush sparking so reduce brush wear. I'd be inclined to replace them.

G6Tanuki · 8th Apr 2021, 7:27 pm

I'd definitely replace the suppressor-capacitors; who knows, you might just have a radio-ham or legacy SW/MW/LW-radio-listener living locally who might come round and poke you repeatedly with a pungee-stick if you blot-out his/her radio-reception.

avocollector · 9th Apr 2021, 12:07 pm

Thanks for those ideas folks - so the answer is clearly yep to replace.

Maarten · 9th Apr 2021, 10:48 pm

Try to find a polypropylene (MKP) replacement instead of a paper cap which might be old stock and fail again soon.

8th Apr 2021, 11:14 am	#1
avocollector Heptode Join Date: Jul 2010 Location: Wellington, New Zealand. Posts: 575	Suppression caps on sewing machine motors - needed? Got a nice metal bodied sewing machine electric motor 230v 5Amp 30 watt model (think it's Sew brand) to use with a minature lathe milling head (Emco Unimat 3 part) I have. Connected it all up to the mains for a tryout and everything was fine except one of the mains suppression caps went bang with a vengence - ruptured and brown goo everywhere. How essential are these to supress rf Tempted to not bother replacing it as the motor will be only used in my shed and on a isolating transformer supply.

8th Apr 2021, 12:49 pm	#2
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 6,079	Re: Suppression caps on sewing machine motors - needed? They might also help reducing brush sparking so reduce brush wear. I'd be inclined to replace them. __________________ On Spike Milligan's headstone......I told you I was ill...

8th Apr 2021, 7:27 pm	#3
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 9,815	Re: Suppression caps on sewing machine motors - needed? I'd definitely replace the suppressor-capacitors; who knows, you might just have a radio-ham or legacy SW/MW/LW-radio-listener living locally who might come round and poke you repeatedly with a pungee-stick if you blot-out his/her radio-reception.

9th Apr 2021, 12:07 pm	#4
avocollector Heptode Join Date: Jul 2010 Location: Wellington, New Zealand. Posts: 575	Re: Suppression caps on sewing machine motors - needed? Thanks for those ideas folks - so the answer is clearly yep to replace.

9th Apr 2021, 10:48 pm	#5
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 3,164	Re: Suppression caps on sewing machine motors - needed? Try to find a polypropylene (MKP) replacement instead of a paper cap which might be old stock and fail again soon.