Re: [CAD_CAM_EDM_DRO] Re: Re: tantalum caps was emc success

ballendo@... wrote:

> Jon,
>
> Thank you for the detailed response. I've only got a few of these out
> there, as their expense meant they were generally "designed out" :-)
>
> But I do have replacement boards which have been "burned in" and then
> sit on a shelf until called for... Would you suggest they be "fired
> up" again before shipment? (puns intended)

Yes, I'd do that. It probably is more of a problem in systems that have
been run for 10 years or so, shut down for a few years, and then fired
up again. I do know of several cases of equipment under maintenance
contract, just a couple of years old, where a tantalum cap burned big
holes in circuit boards. But, I've also run into LOTS of trouble with
industrial-grade gear that ran for years in commercial service, was
mothballed for several years, and then I or someone else got hold of
it and tried to use it for hobby/home shop/home laboratory use, and
had to replace several tantalum caps to get it running. My last run-in
was bringing up the antique Allen-Bradley 7320 CNC control.
When I fired it up for the first time, the power supply kept shutting
down immediately. I pulled boards in various combinations to
isolate the shorted boards, and it was bad tantalum caps every
time. I replaced about 7, I think. Although this was a pretty hefty
power supply, it sensed the overload and shut down before anything
could explode.

Jon