HV PSU caps, modern substituutes? - UK Vintage Radio Repair and Restoration Discussion Forum

Chris Wilson · 16th Aug 2012, 12:51 pm

I am hopefully building a HV PSU from an early 1990's ARRL schematic. The transformer will give , 2.5, 3. and 3.5kV at 1 amp on the secondaries. The schematic and build section shows a 43uF oil filled cap of vast proportions and 4kV rating used for smoothing. Can I duplicate this with an array of more modern capacitors? I doubt I will anything like the original short of finding something surplus in Russia or China!

Thanks.

Sean Williams · 16th Aug 2012, 6:33 pm

Hmm, might be able to help there - will report back later.....

GrimJosef · 16th Aug 2012, 7:40 pm

43uF at 4kV stores nearly 350J so whatever you end up with will inevitably be physically large unless you can use electrolytics, which at this voltage you realistically can't. The cheapest solution using modern capacitors might be to put a lot of motor run polyprops in series-parallel. A 6 'high' by 8 'wide' array of 30uF 470VAC ones like these http://uk.farnell.com/arcotronics/c2...vac/dp/1789706 would give you 40uF at very nearly 4kV. If you bought 50 the total price would still be in the region of £250 though. I imagine that ripple current limits won't be an issue with film caps but it's always worth checking.

Cheers,

GJ

Ed_Dinning · 16th Aug 2012, 9:37 pm

How about some beefy Power factor correction caps from a 3 phase main switchboard in series parallel. Thompson and Siemens make them.

Ed

valveaudio · 16th Aug 2012, 11:34 pm

Chris,
Have a look here.
www.hivoltcapacitors.com/

Trevor

16th Aug 2012, 12:51 pm	#1
Chris Wilson Heptode Join Date: Nov 2011 Location: Whitchurch, Shropshire, UK. Posts: 612	HV PSU caps, modern substituutes? I am hopefully building a HV PSU from an early 1990's ARRL schematic. The transformer will give , 2.5, 3. and 3.5kV at 1 amp on the secondaries. The schematic and build section shows a 43uF oil filled cap of vast proportions and 4kV rating used for smoothing. Can I duplicate this with an array of more modern capacitors? I doubt I will anything like the original short of finding something surplus in Russia or China! Thanks. __________________ Best Regards, CW. 2E0ILY

16th Aug 2012, 6:33 pm	#2
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,517	Re: HV PSU caps, modern substituutes? Hmm, might be able to help there - will report back later..... __________________ Engineers make things work and have spare bits when finished

16th Aug 2012, 7:40 pm	#3
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: HV PSU caps, modern substituutes? 43uF at 4kV stores nearly 350J so whatever you end up with will inevitably be physically large unless you can use electrolytics, which at this voltage you realistically can't. The cheapest solution using modern capacitors might be to put a lot of motor run polyprops in series-parallel. A 6 'high' by 8 'wide' array of 30uF 470VAC ones like these http://uk.farnell.com/arcotronics/c2...vac/dp/1789706 would give you 40uF at very nearly 4kV. If you bought 50 the total price would still be in the region of £250 though. I imagine that ripple current limits won't be an issue with film caps but it's always worth checking. Cheers, GJ

16th Aug 2012, 9:37 pm	#4
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: HV PSU caps, modern substituutes? How about some beefy Power factor correction caps from a 3 phase main switchboard in series parallel. Thompson and Siemens make them. Ed

16th Aug 2012, 11:34 pm	#5
valveaudio Hexode Join Date: Feb 2006 Location: Diss, Norfolk, UK. Posts: 386	Re: HV PSU caps, modern substituutes? Chris, Have a look here. www.hivoltcapacitors.com/ Trevor