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Old 30th December 2006, 06:46 PM   #1
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Default PSU Caps for an EL34 SET

Hi guys,

I am building an EL34 SET with a 450V PSU. I am in search for radial type power caps for the CLC stage. (two 47uF, 500V and one 100uF, 500V) However, I have only come across snap-in type caps online many of which have really short leads and sometimes requiring some mounting hardware. I am trying to keep my construction simple and am using 6 lug terminal strips for point to point wiring on a metal chassis plate. I have some 18ga buss wire. Would it be safe (and possible) to use this copper buss wire to attach snap in type caps to the terminal strips? I intend having all capacitors on the underside of the chassis. I was looking at the Panasonic high voltage caps here. that have short leads? I want to avoid using mounting hardware as it would clutter things up. Alternatively, do any of you know where I could find radial type caps with the ratings mentioned above? The thing is I have never used snap in type caps so I have no idea as to how to work with them. It seems like most 500V rated caps are snap in types for some reason. Any help would be appreciated.

I hope you all are having a fun and chilled out holiday!

Cheers,
Jason.
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Old 30th December 2006, 07:20 PM   #2
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well there are a couple things you can do. personally, i tend to just solder wires to the little prongs on the snap-in caps and use them like a regular capacitor. then again, i always avoid snap-in caps like the plague, preferring the chassis-mount can electrolytics/motor runs or big axials..
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Old 30th December 2006, 09:08 PM   #3
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PCX

Jensen has 40uF and 100 uF axial, but they are expensive.
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Old 30th December 2006, 11:18 PM   #4
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If your normal B+ is 450v, then I suspect that 500v working voltage could be too low for your caps. You need to allow a safety margin, so that no cap will be exposed to excessive voltage if the PS is unloaded for any reason. The penalty for allowing this to happen could be the violent destruction of the cap.

I tend to double up on caps, mainly because I haven't found any with high enough working voltage for my needs. I use two in series, shunted with resistors of 220k or so to equalize the voltages. In your case, you could use a pair of 100uF 350v in series, followed by a pair of 220uF 350v in series. Don't forget the shunt resistors; not only do they ensure equal spread of voltage but they also do a useful job of draining the caps when you switch off.
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Old 31st December 2006, 04:24 AM   #5
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Quote:
Originally posted by ray_moth
You need to allow a safety margin, so that no cap will be exposed to excessive voltage if the PS is unloaded for any reason.
I agree but the more robust your power transformer is, and if you use choke loading, changing current draws become less of a concern.
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Old 31st December 2006, 08:10 AM   #6
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Not sure what you mean by "choke loading". The question was prefaced by the statement "I am in search for radial type power caps for the CLC stage. (two 47uF, 500V and one 100uF, 500V)"
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Old 31st December 2006, 08:52 AM   #7
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Hi !
Do you know Ask Jan first ?

Look here for the caps


Hope this helps !

Simon
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Old 5th January 2007, 05:54 PM   #8
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Default Solen caps it is!

Thanks for all the suggestions guys, I ended up getting the Solen 630V radial caps instead. Changed the PSU a bit as well. Happy New year to you all...
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