Capacitor polarity -- how to tell with confusing markings?

[larry moe 'n curly]

In this picture of four electrolytic capacitors:

http://static.flickr.com/22/93055272_e828b475e8_o.jpg

Which lead is the positive one for each cap?

The black and white dots on the two capacitors on the left are actually
exactly in the middle of the leads.

 

[Damir]

In this picture of four electrolytic capacitors:

http://static.flickr.com/22/93055272_e828b475e8_o.jpg

Which lead is the positive one for each cap?

The black and white dots on the two capacitors on the left are actually
exactly in the middle of the leads.

It looks like coils, not el.caps.

 

[Dave D]

It looks like coils, not el.caps.

They look like tantalum caps to me.

Dave

 

[Damir]

They look like tantalum caps to me.

Dave

Maybe.But too few colors for capacity,polarity and voltage rate.

 

[Ancient_Hacker]

Don't even think of using them.

They're dipped-tantalum capacitors. The positive lead is the one with
the dot.

Problem is, these tend to fail hard and often. They short out all the
time. Either at random or just after a mild overvoltage incident.

And the color codes are hard to interpret.

Which is good for repair guys like me-- I've bought dead oscilloscopes
and calibrators for like $5. Only problem was one to seven shorted
caps, just like the ones you pictured.

 

[Gerard Bok]

In this picture of four electrolytic capacitors:

http://static.flickr.com/22/93055272_e828b475e8_o.jpg

Which lead is the positive one for each cap?

The black and white dots on the two capacitors on the left are actually
exactly in the middle of the leads.

Look at http://www.marvac.com/fun/tantalum_capacitor_codes.aspx

 

[Jason D.]

In this picture of four electrolytic capacitors:

http://static.flickr.com/22/93055272_e828b475e8_o.jpg

Which lead is the positive one for each cap?

The black and white dots on the two capacitors on the left are actually
exactly in the middle of the leads.

Wow! That's very old caps! These design of paint on them dates from
60-70's. In 80's started to use blue, orange or yellow monochrome dip
with printings on it. The latest caps for disk, SMD and drop packages
are now printed with laser etching.

By the way, taluam caps don't take very kindly to long storage. Some
may blow up or short out when power applied to them.

Cheers, Wizard