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 Safety Capacitor Question

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Shanghai Jack



Posts : 4
Join date : 2010-10-20

PostSubject: Safety Capacitor Question   Wed Oct 20, 2010 6:59 pm

Color me confused. My philco 46-350 calls for

.04mf line filter cap
.01 mfpower supply bypass cap
.1 mf line isolation cap

Which ones should be replaced with safety caps, and which ones should be an x and which a y.

Thanks
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Gary (GSI)



Posts : 7
Join date : 2010-10-15

PostSubject: Re: Safety Capacitor Question   Wed Oct 20, 2010 7:15 pm

Jack, the way I always understood it is the .04 line filter cap would be replaced with an X (across the line) and the other two with a Y (line to ground).
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Shanghai Jack



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PostSubject: Re: Safety Capacitor Question   Wed Oct 20, 2010 7:18 pm

Thanks Gary
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burnt fingers



Posts : 70
Join date : 2010-10-12
Location : New Hampshire

PostSubject: Re: Safety Capacitor Question   Thu Oct 21, 2010 6:39 am

You dont want anything over a .01 from line to ground unless a little tingle is OK; its als the current NEC rules. You can place almost anything across the line, I regularly use .047 to .15 to help filter noise and other crud. Mouser carries a combined X-Y rated series in one cap that are very cost effective.

From the HV secondary you might want to reconsider as there are not many choices and a shorted or leaky cap will take out the transformer. I use a .005 to .01 from the rectifier cathode to ground of at least 3X the peak DC voltage to remove any spikes that get thru the transformer. This can be any regular disc or film cap.

Carl
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Gary (GSI)



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PostSubject: Re: Safety Capacitor Question   Thu Oct 21, 2010 3:46 pm

Thanks Carl about the .01 line to ground....I remember Curt saying the same thing a while ago too.
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Shanghai Jack



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Join date : 2010-10-20

PostSubject: Re: Safety Capacitor Question   Thu Oct 21, 2010 7:11 pm

So Carl, let me make sure I understand. You're saying bump the line isolation from .1 down to .01mf.
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oldradioparts



Posts : 23
Join date : 2010-10-13

PostSubject: Re: Safety Capacitor Question   Thu Oct 21, 2010 7:35 pm

can I chirp in and say again... stop using the term "ground" when you really mean "chassis".

A chassis connection is not "ground" unless the chassis is actually tied to ground, and most of us don't do that, and on hot chassis sets you never do it...well, maybe if you rewire the set.

these three terms are not interchangeable but CAN be the same thing on occasion ...

"B-" (B minus)
"Chassis"
"Ground" (or "Earth" outside the USA)

Keep these separate in your mind and descriptions....

Mark Oppat
www.oldradioparts.net
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jack shirley



Posts : 67
Join date : 2010-10-12
Location : SE USA

PostSubject: Re: Safety Capacitor Question   Thu Oct 21, 2010 7:44 pm

Mark's remarks should be a "sticky"...but he left out NEGATIVE in the terminology confusion.
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oldradioparts



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Join date : 2010-10-13

PostSubject: Re: Safety Capacitor Question   Fri Oct 22, 2010 3:20 am

THANKS Jack ! " Negative" should be in that pile for sure !

Mark
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burnt fingers



Posts : 70
Join date : 2010-10-12
Location : New Hampshire

PostSubject: Re: Safety Capacitor Question   Fri Oct 22, 2010 10:37 am

Shanghai Jack wrote:
So Carl, let me make sure I understand. You're saying bump the line isolation from .1 down to .01mf.

Yep, a .1 in perfect condition from hot to chassis ground (the proper term) will pass enough 60 Hz to give you a nice jolt if you grab a real earth ground, another object that is at a different "ground" potential, or even connect a coax from a sig gen there may be a little arc. The .1 going between hot and neutral will do a decent job of noise filtering without getting you excited. affraid

Carl
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oldradioparts



Posts : 23
Join date : 2010-10-13

PostSubject: Re: Safety Capacitor Question   Fri Oct 22, 2010 11:48 am

Carl... just say "from hot to chassis"... dont add 'ground' in there... like I said, it aint ground, its "chassis".

Just trying to get everyone to use those terms correctly.... but its an uphill battle I know....

Mark Oppat
www.oldradioparts.net
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