Electrolytic Capacitor

[W1RKW]

Is there a way to determine the polarity of an electrolytic capacitor besides looking at its markings?  I bought some electrolytics with questionable markings.  The negative lead (which I think is the negative lead) is marked with a dashed line.  The line that I'm assuming is the negative side is more like a line with very small spaces than a line with larger spaces between the lines making it look like they're minus signs.  The rivet is also painted like many electrolytics which typically is the negative side.  An ohmmeter doesn't yield anything concrete so I'm not sure how to determine the right polarity.

[N9NEO]

Hi Bob,

you might be able to put a supply on it and watch the current as you bring it up.  I think when connected the wrong way you will probably see greater leakage current.

Regards,
Bob

PS. Have a great 08.  Wife and I are thinking of renting a place on Lake Hayward for the summer.

[Carl WA1KPD]

Can you post a pic?

[KF1Z]

Drop a 6 or 9 volt battery across it (use a series resistor if you want)...

after 3 or 4 seconds, remover the batt, and put your voltmeter on the terminals... see which is - or +

[WA1GFZ]

I would put a resistor in series with the power supply to limit current. Send me a picture if you can and I will see if I can tell.
a reversed cap will leak and become a resistor. As the cap heats up pressure builds until the seal pops.

[W1RKW]

I'll post something this weekend. 

[WA1GFZ]

Bob, what do you need?

[W1RKW]

Here are the caps in question.  Can I assume that line is the negative side?

[VE7 Kilohertz]

Hi Bob,

I would say you are correct, the black post, with ----- would be negative.

Cheers

Paul

[WA1GFZ]

Agreed.

[W1RKW]

OK, that settles that.  Thanks.