[R-390] Re: Slighty OT: Question about tantalum caps (Barry)

[Ed & Mary Wambold]

Correction:
Barry,

47 mf @ 50v is 47 mf @ 50v, it does *not* matter what type of cap you use, 
unless
you are concerned about physical size. Tantalums are more compact and other
than that, they are equivalent to regular electrolytics...


----- Original Message ----- 
From: "Ed & Mary Wambold" <n3lhb at embarqmail.com>
To: <r-390 at mailman.qth.net>
Sent: Wednesday, September 24, 2008 5:14 PM
Subject: Re: Slighty OT: Question about tantalum caps (Barry)


> Barry,
>
> 47 mf @ 50v is 47 mf @ 50v, it does matter what type of cap you use, 
> unless you are concerned about physical size. Tantalums are more compact 
> and other than that, they are equivalent to regular electrolytics...
>
> Ed, N3LHB
>
>> Message: 2
>> Date: Tue, 23 Sep 2008 20:36:38 -0500
>> From: "Barry" <n4buq at knology.net>
>> Subject: [R-390] Slighty OT: Question about tantalum caps
>> To: "R390" <r-390 at mailman.qth.net>
>> Message-ID: <000601c91de5$fdbe4030$6401a8c0 at ingrnet.com>
>> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>> reply-type=response
>>
>> I think I mentioned on this list that I'm in the process of thinking 
>> about
>> considering the possibility of maybe one day building a 9VDC power supply
>> for one of my radios.  Yes, it's solid state and begins with a "G" (and 
>> ends
>> with "rundig") so if you want to stop reading here, I understand.
>>
>> I was getting the parts list together and the circuit calls for a few
>> miscellaneous caps, one being a 47uF 50V Solid Tantalum cap.  Perusing 
>> the
>> Mouser catalog, I find this capacitor is quite expensive (in excess of 
>> $20
>> each).
>>
>> Can anyone explain to me the advantage of using a solid tantalum over 
>> some
>> other "plain-jane" capacitor?  The circuit uses an LM317K and this
>> particular capacitor is connected across the output just before the 
>> ammeter
>> and voltmeter.  (The circuit is in the 1978 ARRL Handbook (page 127)).
>>
>> I was fortunate to have meters that will make the project nice and 
>> figured
>> that would be lion's share of the cost, but this little cap (along with a
>> couple of other items) have really driven the cost of building this thing
>> nearly out of sight.
>>
>> Can someone/anyone tell me if another type of cap would work as well? 
>> Are
>> the caps of today better than those of 30 years ago, so much so that 
>> maybe
>> the solid tantalum wouldn't be necessary?
>>
>> Thanks!
>>
>> Barry - N4BUQ
>>
>>
>>
>