capacitor polarity?

Jerry Roller · From: Van Buren, Arkansas USA

Brad told me and I forgot. Please someone tell me how to tell + and - on a small capacitor. These have a groove around them near one end and I think that is positive but need to be sure. They have a band running from one end to the other with arrows and I think the arrow is pointing to negative but please tell me for sure someone.
Jerry

Jon Light · From: Saugerties, NY

Jerry---the arrow points in direction of the electrical flow. So the arrow points to negative. I also once knew what the notch meant but that was before I....forgot.

Jerry Roller · From: Van Buren, Arkansas USA

Thanks Jon, now I can proceed.
Jerry

Jim Sliff · From: Lawndale California, USA

FWIW the arrow rule does not always hold true. There are (I have seen several) electrolytic caps with arrows pointing to the positive side, normally with a "+" inside the arrow. I'd never go by a non-marked arrow alone. A couple of other indicators, if no "+" or "_" is marked:

Often caps will have a black end and a shiny end. The shiny end is negative.

Almost all electrolytics have leads of different lengths (this is probably the least known, but the most reliable from what I've experienced). The shorter lead is negative.

I'd suggest looking at all these when installing caps when there's no obvious positive or negative mark.

Hope that helps -
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Jerry Roller · From: Van Buren, Arkansas USA

Thanks guys, I am now in business putting the mod in a Vegas 400. I did a Session 400 a few months ago and Brad led me thru it with a couple of phone calls and several emails but I didn't retain this info in my mind. Thanks for the refresher. I think this one can be CLOSED.
Jerry

Brint Hannay · From: Maryland, USA

In my experience, the groove, if there is one, is always at the positive end. But that's not a promise that it's necessarily universally true.

Jerry Roller · From: Van Buren, Arkansas USA

Yeah Brint, that appears to be the case with the ones I have. I believe the black end being positive is probably one of the most reliable markings as it is insulated from the outside.
Jerry

Jerry Roller · From: Van Buren, Arkansas USA

Yeah Brint, that appears to be the case with the ones I have. I believe the black end being positive is probably one of the most reliable markings as it is insulated from the outside. I have it ready to go back into the cabinet so I will know pretty soon if I did good or not. Question

Jerry

Robert Leaman · From: Murphy, North Carolina, USA

If the capacitor is used for audio coupling, which is very poor design, polarity is meaningless. Electrolytic bi-polar capacitors are available but again this is poor design is usually done in the name of cheap, shoddy design. Polarity is only important when an electrolytic capacitor is used to filter DC voltage points. Electrolytic capacitors act similar to a capacitor with a diode in parallel. If polarity connections are reversed and sufficient current is available, an explosion usually results or the DC power supply and/or power tranformer are ruined because of a near short circuit.

However, non-electrolytics usually have a mark that denotes outside foil wrap. This is lead that needs to connect to the lowest impedance source in the circuit. The outside foil acts as a Faraday shield for the other foil wrap and protects the high impedance point from hum and coupling.

Jerry Roller · From: Van Buren, Arkansas USA

Thanks for all the replies and emails. Job is complete and sounds great to me. This Forum is a wealth of valuable information. Please close this one if you like.
Jerry

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