[GreenKeys] Plantronics tantalums

[David Christ]

This thread appears to be about dipped radial lead tantalum 
capacitors.  What about the tubular axial lead tantalums in a metal 
case with Teflon ends.  Do they have better durability?  Collins used 
them in a lot of aerospace stuff.

And what about the tubular Vitamin-Q caps also with a metal case but 
with glass ends?

Any guidance on either of these?

David K0LUM



At 2:09 PM -0500 11/12/10, 73131.3073 at compuserve.com wrote:
>My experience with Tantalum caps is about the same. However, I have 
>had some luck by bringing up the equipment that contains them with a 
>variac. Starting out at something like 25 VAC for 12 to 24 hours, 
>then upping the voltage by another 25V?for another 24 hours. Keep 
>doing this until you are up to full voltage. Has worked for me. Good 
>luck!
>?
>73,
>?
>Tim Swarthout, WA5QEG
>
>
>
>-----Original Message-----
>From: Geoff Fors <geoff at wb6nvh.com>
>To: Greenkeys List <greenkeys at mailman.qth.net>
>Sent: Fri, Nov 12, 2010 12:54 pm
>Subject: [GreenKeys] Plantronics tantalums
>
>
>
>
>Yes, those are radial lead dip tantalums in the Plantronics 1280 modems, and 
>the same thing happened to me when I first got mine.  It usually occurs 
>after long periods of storage, in all sorts of equipment besides the 
>Frederick/Plantronics.
>
>I replace them with new ones but rated at least 10 Volts higher, which 
>should still fit.  Common opinion is that the modern electrolytics work just 
>as well, if you can find some that fit.
>
>They are used as filters on the various voltage rails in the equipment, 
>which usually (not always) means there is a resistor of about 100 Ohms in 
>series with them, which burns up before they do, after they short.  Without 
>the resistor in the design, they fail most violently and can burn holes 
>through the board, catch fire and send bits of themselves everywhere as 
>miniature projectiles.
>
>There's a silver lining in all of this, namely that I have gotten quite a 
>few pieces of high end, expensive test gear for almost nothing because it 
>was "dead," then easily revived by replacement of a few of these shorted 
>tantalums.
>
>Geoff
>WB6NVH 
>
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