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 Post subject: Can you use a Non Pol capacitor in place of a polarized one.
PostPosted: Feb Fri 23, 2018 10:37 pm 
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Is it possible to use a NP or non polarized capacitor in place of a polarized one..???

Is there any difference between them..

This would be in a vintage transistor radio form the 60's. Im doing a recap and just thought of this...I can use the right one...but would like to know if I can sub...without any change..

Kenny KE4HVE


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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 10:43 pm 
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Kenny

Yes but a non polarized cap will probably be larger.

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 10:54 pm 
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The biggest differences are in the construction and technology---eg paper, plastic, mica, ceramic, and....electrolytics.

For DC filtering, we normally use electrolytics because they are smaller and maybe cheaper than the equivalent film capacitor. Electrolytics are most often polarized, but are also available non-polar (more expensive)

For any specific application, the best choice is often what you see most often---eg you see lots of polarized electrolytics for a reason.

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 11:01 pm 
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Among NP caps, absolutely avoid "motor START" capacitors at all costs.
Those are the cheapest parts that can be called capacitors.

Motor RUN capacitors, on the other hand, are generally of good quality.

- Leigh

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 11:07 pm 
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I can make a very reliable capacitor using two scraps of wire---and the price is right---FREE!!

Now---some nitpicker is going to tell me that we need more than 5 pF......;)

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 11:26 pm 
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pixellany wrote:
Now---some nitpicker is going to tell me that we need more than 5 pF......;)

nothing wrong with 5pf.

You just need an awful lot of them.

- Leigh

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 11:28 pm 
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I assume since we’re talking transistor radios that you mean non-polarized electrolytics in place of polarized ones. Generally speaking that will work. ESR is greater with polarized caps, but that doesn’t matter much in coupling circuits. Might make a difference for bypassing, or not. But they are bigger and more expensive, so not sure what is really being gained?

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Fri 23, 2018 11:35 pm 
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Leigh wrote:
pixellany wrote:
Now---some nitpicker is going to tell me that we need more than 5 pF......;)

nothing wrong with 5pf.

You just need an awful lot of them.

- Leigh

Friday night seems like a good time for off-topic levity----There is capacitance everywhere you look---all FREE. What we pay the big bucks for is get it in the right place.

But also, some device designers spend really big bucks to get rid of capacitance.

Are you perhaps suggesting that a filter cap made with my wire scraps might be a bit large???

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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Sat 24, 2018 12:00 am 
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There is only 4 electrolytic caps in this radio...the radio is a GE p-810A. It had axial caps and I had NP axial caps to use in it..since the spacing on the axial caps is very wide physically, It was easier to use the NP axial instead of the radial ones...In other words at the moment I had NP axial caps, and no polarized axial ones to put in.

K


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 Post subject: Re: Can you use a Non Pol capacitor in place of a polarized
PostPosted: Feb Sat 24, 2018 12:19 am 
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Joined: Dec Tue 08, 2015 12:53 am
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Location: shirley NY...Long Island
Seems like every ge radio I work on has that useless antenna with the wire wrapped around the ferrite core...It is wrapped all the way the ferrite bar from end to end..and it never works right...I have to attach an external wire..or just lay a wire next the bar and then it works as it should...what is up with that????????????

K


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