AW: multiple power supplies in a modular

[Barry L Klein]

> I would not use tants. When these die due to a fault or whatever, they
> tend to go short. If you conect these directly across your rails, then
> its goodbye regulator and hello to burnt pcbs. Ordinary electrolytics
> (elec's...?) are fine for this I would have thought, especially if you
> put a low value cap in parallel with it.

   Hate to break it to you, but electrolytics will do this too.  :)  
We use tantalums in our disk drives here at WDC.  We ship em by the millions.  Investigating tantalum failures on drives was my task for awhile.  I found that many of the pc supplies had faulty AC grounds.  Tantalum failure is due to either a bad part - but that will be likely caught at the cap. factory, or overvoltage in the application.  We've been using tantalums in drive for over 8 years (how long I've been here) and they continue to work - imagine what would happen if they all were to die in 8 years!  Electrolytics on the other hand, don't have such a good long-term reliability reputation.
Just talk to guys that repair guitar amps etc. and read the LinTech notes.

So if you want to find a cheap source of tantalums check out all those obsolete ISA cards or hard drives.  They're usually surface mount but have large pads so you could solder wires to them with no problems.

As a result of my work, we put TVSD's across the drive supply lines.  These will clamp any overvoltages.  You might want to try these things on your supply lines etc.  They seem to be worthwhile.  Definitely have improved reliabilty of the product.  And I think only ours have em....(plug)  :-)

Barry