[GreenKeys] Plantronics tantalums

[73131.3073 at compuserve.com]

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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