I hate Tantalum c(r)aps!

[anotherjim]

I always have distrusted them and yesterday I caught one out. Not a stomp project, but an MCU board. With no chip fitted and no load, I was checking a first power-up and noticed the pin with the ADC reference was a lower voltage than expected. It's fed thru a resistor off 5v and the only load is a tant cap (used to save headroom as there isn't going to be a lot of clearance above the board). Had to be the cap leaking and it was. So it was only 0.6mA, but that seems bad for running off only 5volt. I felt it was a sign I couldn't trust it.
I'd had it in stock a while, but I think it came from RS components originally. It's not the first Tant I've found bad over the years and not the first I've caught out in early testing. So I've had with the buggers!

[duck_arse]

it's funny you should have a dud tant, too. in the cloks thread:
http://www.diystompboxes.com/smfforum/index.php?topic=112663.0

my C6 in the REV0.0 circuit on the bb was a tant. with my initial how-it-works confusion, it may have been backwarded, but once I had some voltages it was fitted the right way. only, now the power supply is dropping to about 6 volts, and buzzing (the transistors didn't care, just kept pumping out the volts). why is the circuit drawing so much current, yet no smoke/heat/light?

so I pulled the cap, tested short, threw into bin. it was old anyway .....

[Bill Mountain]

I bought a bunch of 1uF and .47uF tants for some projects to try them out.  The 1uF were fine but every single .47uF was leaky and I could hear it crackling through every circuit I tried them in.  I want to love them for their size but I'm a little hesitant now.  Is it possible the smaller value ones aren't as good as the higher value ones?

[wavley]

This is actually part of my thought process when troubleshooting repairs of an unknown piece of gear.  The power rails don't look right, does it have tants?  I see those and small ceramic decoupling caps near chips go shorted the most, and tants definitely win (loose?) the contest.

Although, there are circuits that benefit from tants due to their small size and low ESR particularly in high speed and microwave stuff.  Save them for those places, and even then if I have the space a low ESR electrolytic or electrolytic bypassed by a ceramic is my preferred method.   

[amptramp]

If you check the design of some tantalum caps, there is a line that goes to the positive side.  Aluminum electrolytics have a line going to the negative side.  Any chance some of your caps are in backwards?

[blackieNYC]

Tant failures are usually shorts. There's a nice article on the physics of it in this forum somewhere.

[mremic01]

Do tants go bad over time like aluminum electrolytics, or are they just really really susceptible to damage? I'm ok with a fragile part that's fine as long as it's not abused, but the idea that a part is guaranteed to fail in the next 20 or so years doesn't sit well.

[alfafalfa]

Tant failures are usually shorts. There's a nice article on the physics of it in this forum somewhere.

I've used them for a couple of decades now and usually they behave well but I have also seen one or two go up in smoke for no particular reason.

[anotherjim]

I think they were old, but unused & clean. Branded STC with a clearly legible "+" over the pos leg and shaped with the usual tantalum pregnant bulge over the + leg.

[duck_arse]

usual? in my mediocre experience, I'd say the bulge was unusual. I had a bag of ITT tants, they all went jitter noisy when used as supply bypass, so they went bin-wise too. and they were old.