Capacitor question

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Posted: 2/7/2006 6:38:05 PM EDT

I am trying to build a Code Practice Oscillator to learn morse code and got a question.

On an electrolytic capacitor is the polarity mark with the neg (-) only?
On one side it looks like a (-) but the wrap is a little distorted and can not tell. I can not see any Markings for pos (+) at all.

73
Bobwrench

Posted: 2/7/2006 6:41:38 PM EDT

[#1]

Small electrolytics are usually marked only with a (-). Big, computer grade electrolytics are usually marked with both (+) and (-).

IIRC, tantalums are usually marked with a dot to denote (+).

Posted: 2/7/2006 6:46:35 PM EDT

[#2]

Quoted:
Small electrolytics are usually marked only with a (-). Big, computer grade electrolytics are usually marked with both (+) and (-).

IIRC, tantalums are usually marked with a dot to denote (+).

Thanks that maybe why it doesn.t work. I'll go back and see if I need to make the change. I could not get it to work and had to put it down for a while. I checked the circut diagram and it seems right , the olny question I had was the polarity.

Bobwrench

Posted: 2/7/2006 6:47:16 PM EDT

[#3]

and some are marked with a arrow like pattern pointing to the pos ( showing current flow direction )

Posted: 2/7/2006 6:49:07 PM EDT

[#4]

Usually only the neg is marked on an electrolytic... Is there any reason you are stuck on an electrolytic? Nonpolarized caps are superior wrt to accuracy and hf.

Posted: 2/7/2006 6:58:18 PM EDT

[#5]

Quoted:
that maybe why it doesn.t work.

I've seen electrolytics and tantalums that were mis-installed and the circuit still worked. In fact, a few worked for a long period of time as long as they weren't run near their max operating voltage.

In a low-voltage, low-stress audio oscillator circuit, I'll bet something else is wrong.

Posted: 2/7/2006 7:11:42 PM EDT

[#6]

Quoted:
Quoted:
that maybe why it doesn.t work.

I've seen electrolytics and tantalums that were mis-installed and the circuit still worked. In fact, a few worked for a long period of time as long as they weren't run near their max operating voltage.

In a low-voltage, low-stress audio oscillator circuit, I'll bet something else is wrong.

Yea...and I've seen low-E high current DC power supply caps EXPLODE like a rifle shot if they are installed backwards too.

The damage to the supply was most impressive.

Posted: 2/7/2006 7:19:26 PM EDT

[#7]

Yup. The input filter caps on a switching power supply will blow up real good. They'll spray paper, plastic and foul-smelling oil all over the place.

Posted: 2/7/2006 8:05:21 PM EDT

[#8]

Quoted:
Usually only the neg is marked on an electrolytic... Is there any reason you are stuck on an electrolytic? Nonpolarized caps are superior wrt to accuracy and hf.

This is a code practice oscillator, not hi fi gear. Aluminum electrolytics are a tiny fraction of the cost and size of various non-polarized film caps. It would be rather silly to use anything else in such a circuit.

(Ed, I am my own spelling Nazi)

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