Using X2 caps as capacitive droppers - UK Vintage Radio Repair and Restoration Discussion Forum

paulsherwin · 31st Aug 2005, 12:24 am

I realized today that I have quite a few X2 rated caps scavenged from old switch mode PSUs etc. Some of these are quite big values - there are lots of 0.47uFs and at least one 1uF. Can anybody think of a reason not to use these as capacitive heater droppers, rather than the traditional motor run caps? They're generally rated 250VAC.

TIA, Paul

GMB · 31st Aug 2005, 10:50 am

I think they are ideal for it. As you say, they are continuously rated for mains voltage a/c.

Radio_Dave · 31st Aug 2005, 11:14 am

Hi Paul, yes I added them in parallel with a motor run cap to give me the exact value needed

David

Ed_Dinning · 31st Aug 2005, 12:19 pm

Hi Paul, when I wrote an article for Radiophile many years ago on capacitive droppers these were the only types available. They work very well and are available in a range of values. Additionally they are self healing so do not fail to an S/C (athough they will allow a surge throgh) so are better than a motor run cap which usually has a fuse inside and can let a lot more energy through to your precious set.

Ed

Paul Stenning · 31st Aug 2005, 11:00 pm

I can see no problems using X2 caps. The main reason why I tend to recommend motor caps is that they are available in higher values than X2 types (you often need between 1uF and 2uF).

As Dave mentioned, X2 caps are useful to add in parallel with a motor cap to achieve the correct value. The yellow 1000V polyprop ones should be fine too.

31st Aug 2005, 12:24 am	#1
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Using X2 caps as capacitive droppers I realized today that I have quite a few X2 rated caps scavenged from old switch mode PSUs etc. Some of these are quite big values - there are lots of 0.47uFs and at least one 1uF. Can anybody think of a reason not to use these as capacitive heater droppers, rather than the traditional motor run caps? They're generally rated 250VAC. TIA, Paul

31st Aug 2005, 10:50 am	#2
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,100	Re: Using X2 caps as capacitive droppers I think they are ideal for it. As you say, they are continuously rated for mains voltage a/c.

31st Aug 2005, 11:14 am	#3
Radio_Dave Nonode Join Date: Jun 2004 Location: Norwich, Norfolk, UK. Posts: 2,543	Re: Using X2 caps as capacitive droppers Hi Paul, yes I added them in parallel with a motor run cap to give me the exact value needed David

31st Aug 2005, 12:19 pm	#4
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Using X2 caps as capacitive droppers Hi Paul, when I wrote an article for Radiophile many years ago on capacitive droppers these were the only types available. They work very well and are available in a range of values. Additionally they are self healing so do not fail to an S/C (athough they will allow a surge throgh) so are better than a motor run cap which usually has a fuse inside and can let a lot more energy through to your precious set. Ed

31st Aug 2005, 11:00 pm	#5
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,073	Re: Using X2 caps as capacitive droppers I can see no problems using X2 caps. The main reason why I tend to recommend motor caps is that they are available in higher values than X2 types (you often need between 1uF and 2uF). As Dave mentioned, X2 caps are useful to add in parallel with a motor cap to achieve the correct value. The yellow 1000V polyprop ones should be fine too. __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster