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Onelasttime
Junior Member
Username: Onelasttime
Post Number: 42
Registered: 8-2011
| | Posted on Sunday, September 04, 2011 - 2:30 am: | 
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I can get Teflon Capacitors for less then the cost of Electrolytic. Military Surplus locally from National Guard Surplus they where intended for Avionic in Fighter Jet's and Helicoptor's.
SO now the question. I am restoring/modifying 10/6 meter linears. I will be using these caps for filtering and storage on the AC side and DC side. My most immediate use will be after the rectifier board for DC filter and and storage. I have always in the past used computer grade Electrolytic for power filtering and immediate storage. The price is too good to say no too but I still want to make sure I can use them any place where their rating is needed. I am guessing they are No-Polar and in DC filtering and in AC rectifiers I have normally used polar electrolytic.
I can get them in the case (35) per casefor about the price of 3 Sprage Atomics of equal capacitance and voltage. |
Tech833
Moderator
Username: Tech833
Post Number: 2038
Registered: 8-2002
| | Posted on Sunday, September 04, 2011 - 4:54 pm: |
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Nice!
Care to pick up some for a friend???
Your radio 'Mythbuster' since 1998
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Tech237
Moderator
Username: Tech237
Post Number: 1468
Registered: 4-2004
| | Posted on Sunday, September 04, 2011 - 10:37 am: |
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I'd follow the age old wisdom of "if I'm not sure I don't do it, until I have experiemented on a non-essential piece of equipment".
Personally I have never seend non-polarized caps used in power supply filtering, BUT, they may simply be that until reasonably recently you could not get large enough caps that were not polarized.
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Onelasttime
Junior Member
Username: Onelasttime
Post Number: 45
Registered: 8-2011
| | Posted on Monday, September 05, 2011 - 12:47 am: |
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Well normaly you can not afford to buy a Teflon Cap inthe 500 Volt 100mfd rating.....You would have to have mighty deep pockets. I think I have seen some in the 50V-100V range in like .47mfd sell for $50 each if I recall properly. So if you are building a $3000-$10,000 dollar tubed audio amp for a guy with deep pocket's and sensitive ear's or if you have to have insane low ESR and narrow diletric values in say a 30 Billion dollar Stealth Bomber they make sense!
I am thinking about picking up a case I think I can get a case for about $40 I do not know how many they have though. A friend told me about it.
I have two sources so if this one dry's up I will post the other source for those interested.
A lot of computer grade snap in, twist in or bolt in electrolytic are non-polar but again they are so darn expensive that I have never used that kind in anything other then a repair of main frame that already had that type in it.
If not for the price I would not be considering it because to be honest I am guessing that in this application I will not see any benefit besides the insanely cheap price. Obviously 35 of something that are better then you normally use for the same price as 3 is a good deal that is almost in the area of 10 for the price of one!
Each one will still have a diode and resistor spanning the contacts so even though the caps might not be polar their is no way with the diode and resistor spanning the cap for the voltage to feed backwards.
If my antron 99 starts glowing or I see blue smoke I will know I made a mistake! LOL
I think it will be fine but I would of liked to have had some first hand experience from one of you guys!LOL Brains are great but experience is even better!I am lacking the experince in this area!!!LOL |
Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 297
Registered: 5-2002
| | Posted on Monday, September 05, 2011 - 9:43 am: |
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"Each one will still have a diode and resistor spanning the contacts so even though the caps might not be polar their is no way with the diode and resistor spanning the cap for the voltage to feed backwards."
Never heard of a diode spanning the cap, just the use of a bleeder resistor. New one on me.
Dyslexics of the world UNTIE!
73 De Bubba Honorary O.F.
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Tech833
Moderator
Username: Tech833
Post Number: 2039
Registered: 8-2002
| | Posted on Wednesday, September 07, 2011 - 10:56 am: |
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A diode across a cap is not at all uncommon in circuits where a sudden power down could damage components downstream of the cap. It eliminates current flowing the other direction, which would be the wrong direction for the components (usually voltage regulators).
Your radio 'Mythbuster' since 1998
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