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 Post subject: Tubular ceramic capacitors
PostPosted: Sep Mon 20, 2021 10:34 pm 
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Joined: Jan Thu 07, 2021 10:41 am
Posts: 87
My Schaub Lorenz Rialto Stereo 10 has a number of tubular ceramic capacitors. A few questions.
1) Are these generally reliable?
2) They are usually low pF values, the same radio also uses low pF value polystyrene caps. Why sometimes polystyrene and sometimes tubular ceramic?
3) if they do need replacing would silver mica be suitable?


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 Post subject: Re: Tubular ceramic capacitors
PostPosted: Sep Mon 20, 2021 10:40 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 10799
Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
I have never seen a tubular ceramic capacitor that had become defective in the way that paper capacitors do. I have seen a couple that have broken in the middle of the bodies.


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 Post subject: Re: Tubular ceramic capacitors
PostPosted: Sep Mon 20, 2021 10:56 pm 
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Joined: Nov Tue 14, 2017 5:09 am
Posts: 4014
Location: Austin, Texas
If this type of cap isn't broken, it has a 99% chance of being good. The ceramics are usually employed where the value needs to be stable with temperature changes. That is almost always in a tuned circuit. For those applications, a silver mica is a good replacement.

There are applications where the ceramic cap is supposed to change value with temperature to compensate for other parts in the resonant circuit. The schematic or parts list will usually indicate when a special temperature coefficient is needed.

Jay


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 Post subject: Re: Tubular ceramic capacitors
PostPosted: Sep Mon 20, 2021 11:23 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 5097
Location: Melbourne, Florida
Don't mess with them. They are some of the most reliable parts ever.

RRM


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 Post subject: Re: Tubular ceramic capacitors
PostPosted: Sep Mon 20, 2021 11:59 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 27847
Location: Detroit, MI USA
I agree they are extremely reliable. Don't move them, don't desolder the leads, don't attempt to test them, just leave them exactly how you found them until and unless you have an operational problem that can be traced to one.

You are also not likely to be able to find replacements for any that have special temperature compensating characteristics.

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Dennis

Experience is what you gain when the results aren't what you were expecting.


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 Post subject: Re: Tubular ceramic capacitors
PostPosted: Sep Tue 21, 2021 1:52 am 
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Joined: Jul Mon 08, 2013 2:48 pm
Posts: 794
^^^^ All the above is correct: these tubular ceramic caps are ultra reliable if not put under mechanical stress. Just leave them as they are.
Since their tempco characteristics are unknow and could be an important factor in some parts of the circuit replacement could be problematic and is not recommended.


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 Post subject: Re: Tubular ceramic capacitors
PostPosted: Sep Tue 21, 2021 2:14 am 
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Joined: Sep Mon 16, 2013 2:42 am
Posts: 5072
Location: Tucson, Arizona U.S.A.
Polystyrene capacitors are also extremely reliable unless they are abused. Leave them alone as well. Be careful not to touch them with a soldering iron; they melt. Be careful not to get any solvent on them: they dissolve.

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Who's that swimming in the punch bowl?
It's Walter Wart, the freaky frog!


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