Tantalum cap help

[Al Heeley]

I got these tant caps (2.2uF) for a Small Clone chorus build.

Now Tantalum caps are supposed to be polar, right? One leg + the other -ve, but I don't know which way round these should sit as there's no other marking on them.
I'm assuming if I get it wrong the circuit won't work.
Any advice please?

[R.G.]

I got these tant caps (2.2uF) for a Small Clone chorus build.

Now Tantalum caps are supposed to be polar, right? One leg + the other -ve, but I don't know which way round these should sit as there's no other marking on them.
I'm assuming if I get it wrong the circuit won't work.
Any advice please?

You assume correctly. Tantalums are much less tolerant of reversed voltage than aluminum - and aluminum hardly tolerates it at all. Tantalum start failing at a slightly higher reverse voltage than aluminum, but it's more spectacular when it does fail. Put it in backwards, it will fail. I've never seen a NP tantalum, not that there can't be.

The only thing I can think of is that one leg is bent/kinked a little different from the other. However, that will be small comfort.

The big guys used to have problems with tantalum caps going up in flames on well-powered logic boards. So much so that they had the makers of tantalum make three legged devices where the outer caps were one polarity, the middle one the other polarity, so it could not be put in backwards without bending the leads around.

I'd get my  supplier to tell me what the super secret markings are, or get a refund. On average, you'll kill half of them. 

[Brymus]

Isnt the negative lead supposed to be shorter than the positive one ?
Did you cut the leads already ?

[Steve Mavronis]

'Polarized' tantalums are supposed to be marked which lead is + like this one:

[Brymus]

'Polarized' tantalums are supposed to be marked which lead is + like this one:

So are you saying his are non polarized ?

[Steve Mavronis]

I don't know, maybe? My only recent experience are with the polarized ones. Hopefully someone else can chime in to clarify if his are or not to help him.

[zombiwoof]

I'm sure the bent lead is supposed to indicate polarity, the obvious problem is that one doesn't know exactly which polarity it indicates.  There should be some way to figure it out, but I don't know enough to tell you.

Al

[Al Heeley]

the legs havent been snipped - they are all like this. I have heard you can get non-polarised ones but the circuit calls for polarised. Surprised theres no markings, other types of tant caps I bought before have the tiny + sign on them. Maybe I can just use an electrolytic cap instead? Its the tonepad small clone circuit, cap in question is top left on the layout.
http://tonepad.com/getFile.asp?id=97

[Hides-His-Eyes]

I'd just assume the kink is on the negative; not because of any prior knowledge, just because on an LED the flat side is negative, and so if I was a manufacturer, I'd "mark the -ve side".

[Unlikekurt]

If you read the build reports on tonepad site for the small clone you'll see that a lot of folks have done that build without polarized caps and had no problem. 

[slacker]

Semi serious suggestion, like R.G. said you've got a 50/50 chance of putting it in the right way round, so just slap it in there. If it explodes, then replace it with an electro if it doesn't then every thing's groovy

[Al Heeley]

Thx guys, I'll shove it in and see what happens. What I hate is when it doesn't work, is it down to the cap or some other problem like a poor solder somewhere else....the joys of debugging. At least if I know all compnents are correct and right way round I can narrow down the debugging.

[Unlikekurt]

Have you a multimeter that can measure capacitance?
If so, you might have a solution right there.  It'll only read in the correct direction.

[GibsonGM]

I'm gonna take a stab at it...I think the 'kinky' leg, on the right, is "+".   Don't ask me why I don't think it's "-"....

[CynicalMan]

It might just be the photo angle, but it looks as if there was a third leg, like RG mentioned, and it was broken off.

[waltk]

The only thing I can think of is that one leg is bent/kinked a little different from the other.

If I had to make a guess, I'd go with R.G. on this.  Also...

I'm gonna take a stab at it...I think the 'kinky' leg, on the right, is "+".

My guess is - just the oposite.  Because the longer lead is generally the + one, and in the absence of other evidence, a greater "kink" would make a leg shorter, I would guess the kinkier one is the negative lead.

I also have some evidence for this.  I have some tantalum caps that ARE marked, and have one leg more kinked, and the kinked leg IS negative.

I have large stock of 35V 2.2uF tantalum caps (measuring 2.21 uF .012 Q @ 1000Hz) that are marked.  If you live in the US, PM me with your address, and I'll put some in an envelope for you (gratis).

[waltk]

I have large stock of 35V 2.2uF tantalum caps (measuring 2.21 uF .012 Q @ 1000Hz) that are marked.

Quick clarification the "Q" mentioned above is actually the dissipation factor (inverse of Q).  The low DF in these is desirable.

[stringsthings]

the legs havent been snipped - they are all like this. I have heard you can get non-polarised ones but the circuit calls for polarised. Surprised theres no markings, other types of tant caps I bought before have the tiny + sign on them. Maybe I can just use an electrolytic cap instead? Its the tonepad small clone circuit, cap in question is top left on the layout.
http://tonepad.com/getFile.asp?id=97

i believe that you can use an aluminum electrolytic in place of a tantalum electrolytic .... just match the capacitance value and the voltage rating ... ( you can always use one that's rated at a higher voltage )

[Al Heeley]

just bought some 'proper' polarised tant caps, now trying to get my small clone debugged.

[Ice-9]

I would just wire it to a battery and leave it to pop somewhere safe of course, (if it's the wrong way) this way you will know for the rest of the caps which lead is which.