[R-390] OT: Wet or Solid Tantalum?

[eldim at att.net]

The one pictured on the ebay  acution in the UK is a U.S.A. Manufacted Tantalum (sintered wet slug), but only very mildly wet if memory serves me correctly.  If they have a silver casing, and I do mean real (silver), then the solid tantalum slug inside is machined smooth and is connected to solid tantalum wire that exits thru a Teflon bushing.  This is a wet type that has a Potassium-Hydroxide (alkaline) solution to form the electrolyte.  This last type of Tantalum is known for it very high accuracy, stability and does not change with altitude, and temperature.  I have a brochure from one of the major areospace from years ago buried somewhere in my library which is blocked at this time. Tantalum come in rod form, solid wire, and foil.
The prettist is the two different colored foil sheets that is spooled in the TANTA-LEX electrolytics manufactured by GE which is encased in an aluminum cased with axial welded leads.  The two Tantalum foil types are seperated by a wet impregnated paper (that stinks), but is required to form the dielectric.

Hope that this info helps and is correct as my memory is slipping.
73,
Glen Galati, KA7BOJ
Tacoma, Wa.
eldim at att.net
253-272-1061
-------------- Original message from rbethman <rbethman at comcast.net>: -------------- 


> Barry, 
> 
> Yep! That's THE one! The reason they eat the board is the "old" wet 
> tantalum capacitors had an acid electrolyte. 
> 
> Bob - N0DGN 
> 
> Barry wrote: 
> > On Mon 10/11/08 2:20 PM , "Bill Hawkins" bill at iaxs.net sent: 
> > 
> >> IIRC, the wet tantalums that I've seen in 60's HP gear have a larger 
> >> diameter at one end for the electrolyte seal. That's where the gunk 
> >> gets out and messes up the circuit board. 
> >> 
> >> The ones in England, with the blurry photo, are almost certainly 
> >> solid electrolyte caps. 
> >> 
> >> Bill Hawkins 
> >> 
> > > Is that little bell-ended cap (the one that has usually leaked) on the PC 
> board in the AF deck on an R390A a wet tantalum? 
> > 
> > Barry - N4BUQ 
> > 
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> 
> -- 
> Bob - NØDGN 
> 
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