Swap old tantalums for new electrolytics? - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

PJL · 1st Sep 2017, 5:47 pm

The problem with tantalums is most don't explode. They happily sit there with their zero resistance and zero dissipation giving no clue that they are the cause of the fault condition. Most other capacitor types show signs of failure, exploding, glowing, oozing wax/electrolyte, or dropping bits of distorted brown plastic casing.

mhennessy · 1st Sep 2017, 6:23 pm

I can't recall one ever doing that. The only failures I can think of have been across rails, as discussed earlier in the thread.

Still, a s/c cap will change the circuit conditions in a way that will lead you to it eventually. Perhaps someone less trusting than me would cold-check all tants in circuit before applying logic...

I read the famous LLJ "The Gypsy's Warning" (beware the blue tants) long before I saw my first tant, so was expecting the worst. Perhaps I've been lucky, but they've been pretty good to me over the years. We did have an SMT tant fail in an MPEG encoder at work about 10 years back, which caused a building evacuation and other drama - I still have the burnt-up PCB and show that to delegates - but on the whole, I get on OK with them. I've never had one fail in any of my projects (though if they did, fuses or resistors will take the hit).

1st Sep 2017, 5:47 pm	#41
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Swap old tantalums for new electrolytics? The problem with tantalums is most don't explode. They happily sit there with their zero resistance and zero dissipation giving no clue that they are the cause of the fault condition. Most other capacitor types show signs of failure, exploding, glowing, oozing wax/electrolyte, or dropping bits of distorted brown plastic casing.

1st Sep 2017, 6:23 pm	#42
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Swap old tantalums for new electrolytics? I can't recall one ever doing that. The only failures I can think of have been across rails, as discussed earlier in the thread. Still, a s/c cap will change the circuit conditions in a way that will lead you to it eventually. Perhaps someone less trusting than me would cold-check all tants in circuit before applying logic... I read the famous LLJ "The Gypsy's Warning" (beware the blue tants) long before I saw my first tant, so was expecting the worst. Perhaps I've been lucky, but they've been pretty good to me over the years. We did have an SMT tant fail in an MPEG encoder at work about 10 years back, which caused a building evacuation and other drama - I still have the burnt-up PCB and show that to delegates - but on the whole, I get on OK with them. I've never had one fail in any of my projects (though if they did, fuses or resistors will take the hit).