I have a Racal 9301A where a tantalum must have caught on fire because all
that was left was 2 leads, some crisp blackish ash and a little hardened
crust on the pcb where it burned. There's probaby 10 other tants on the
board and one or more are shorted but still intact and I'm trying to find
the bads one/ones with least effort without a schematic. The other unit is
a Wavetek 188-S1257 where a tantalum had a dead short but was intact. I
repalced it with an electrolytic. The cap is on a 15 volt rail where I
think it shorted and took out the regulator. Ireplace the regulator with
what I assumed was a good one out of a new box but it was bad and it put 23
volts on the rail that had a 20 volt rating but no more failed. Sometime I
have good luck.
73
hank wd5jfr
"John Larkin" wrote in
message ...
On Wed, 21 Jan 2004 17:26:14 -0600, "Henry Kolesnik"
wrote:

Over the last few years I've acquired quite a few consumer electronincs
pcbs
including TVs, VCRs, stereos, etc, so when I discovered that I needed a
tantalum to repair some test equipment I was going to salvage a tantalum.
I
couldn't find one anywhere, so I assume they're too expensive or too
unrelaible for high end consumer electronics. A couple of the boards
were
from my personal stuff purchased new. One example is a MGA Mitsubishi
rear
projection TV that operated flawlessly for nearly 20 years of daily use.
Most of my test equipment comes from hamfests and is surplus after
becoming
obsolete and non-operative in less than 20 years. That leads me to
wonder
what the real story is behind tantalum capacitors. What do the experts
have
to say?
tnx
hank wd5jfr


We often use surface-mount tantalums on high-density, high-cost
boards. They are very reliable (don't dry out like aluminums) if used
carefully, but high peak currents can ignite them, so they are
generally a bad idea for bypassing power rails.

Polymer aluminums (don't dry out) or polymer tantalums (don't explode)
seem like a good idea, but I haven't tried them yet.

I think multilayer ceramics are pushing 100 uF these days.

John