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Old 2nd October 2003, 02:42 AM   #1
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Default Help with identifying some caps and their values on a phono preamp

http://www.coasterreview.com/phono/?...ze=725&start=0


Anyone able to identify the two silver caps on that board?
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Old 2nd October 2003, 03:36 AM   #2
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Default Capacitor type.

If you mean what type they are : - they were called styroflex capacitors over here. I never knew why it was called that.
One doesn't find them nowadays in this market.
If you mean values , you might have to rotate them around. The value is usually mentioned quite clearly . I have several of these types ( old stock !).
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Old 2nd October 2003, 04:16 AM   #3
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Default Forgot some details.

These are metal film caps unlike the metallised foil that is very popular today. Basically I think they are made with two metal foils and a plastic film rolled up into a roll. I have no idea how good it is compared to modern day film caps. But I have seen 2.5% types and so they must be pretty good I think.
I have seen values from 100pF to just over 0.01uF.
If the circuit is a phono preamp, you could check the resistor values and calculate the cap values . It looks like a standard phono feedback circuit.
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Old 2nd October 2003, 04:35 AM   #4
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Big one (black)seem to be Solen cap.
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Old 2nd October 2003, 02:58 PM   #5
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It seems like you already have the values on the attached schematic. Here's the equasions which you can use to check if the values are correct.

This is a pretty nice album and the phono stage looks very nice too (the way it's put together). You can use any quality caps and the better ones will improve performance. As to coupling caps, they look indeed like Solens, and again, you can use better ones here.

Do you have any more albums like that?

Edit: 270 and 75 should be followed by " = " which is missing in a drawing.
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Old 2nd October 2003, 04:39 PM   #6
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Here in America they are known as Polystyrene capacitors. They are available in 1% to 5% and are very nice caps - fairly inexpensive as well.
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Old 2nd October 2003, 04:48 PM   #7
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And still available from Partsconnexion: http://www.partsconnexion.com/catalog/capacitors.html
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Old 2nd October 2003, 05:04 PM   #8
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Default Polystyrene

These sliver caps are low cost Polystyrene film caps. These are made by a number of different companies. Polystyrene is a good material for small signal caps.

You can purchase much higher quality Polystyrene caps but not in all values.
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Old 2nd October 2003, 05:44 PM   #9
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I don't believe polystyrene caps are made much anymore due to there poor resistance to many solvents. I also heard that the only remaining vendor of good PS film has stopped manufacturing it. They are foil and film and I don't believe you can metalize the PS dielectric. They are my favorite type cap and I have seen them up to about a uF for audiophile type caps. Have yet to find a Silver Mica sound better than a good PS in anything I have modified. For small values the old Siemens Styroflex were some of the best. For those who still think they are commonly available go try to buy a bunch of new (not surplus) 4700 pF PS caps.

I believe 0.0027uF (2700 pF) and 27K ohms is what comes close to the 75 uS time constant. The exact value would be 2778pF for the precision people and could be a selected 2700 pF cap or selected 27K resistor picked to match the cap value.
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Old 2nd October 2003, 05:52 PM   #10
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I think styroflex as a material is not produced anymore.
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