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Old 25th July 2010, 01:33 PM   #1
GeeVee is offline GeeVee  Australia
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Default Help to identify capacitor composition

Hi all
I am wondering if I could get some help in identifying the capacitors as shown in the picture. I have searched the internet, but can’t find a lot of info.
I would be very interested to know the type / composition.
I purchased large quantities of these types of caps some time ago, from a now defunct surplus store.
So far this is what I have been told / been able to work out, but I could be wrong.

Cap.1 - I was told that it is a silver mica, but I have never seen them this shape. No other markings, other than what is printed.

Cap.2 – As above, and looks to be very similar construction to type 1. However this one has “ITT-273” stamped on the back.

Cap 3 – Now this one I am sure is a silver mica. Has “Lemco” stamped on the back

Cap 4 – No Idea.

Cap 5 – No Idea, has marking “MFD Precision Capacitor”

Any help will be greatly appreciated

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Last edited by GeeVee; 25th July 2010 at 01:35 PM. Reason: upload pic
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Old 25th July 2010, 05:03 PM   #2
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Number 4 appears to be an ordinary mica capacitor. Number 5 is perhaps a metallized paper or mylar, not marked MFD as you say, but marked 1 MFD. There is a 1 there. MFD is a substitute for microfarad.

The first two look like Vitramon ceramic multilayer capacitors and the third one looks like an ordinary mica but there were several types made that look like that. Except for the ribbon leads - that's strange.
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Old 21st February 2011, 11:58 AM   #3
djQUAN is offline djQUAN  Philippines
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I got a bunch of these caps and wanted to know what dielectric they are. searching the net made me think it's PPS? but not entirely sure.

Anyone know what they are exactly? (the grey square ones with no plastic encapsulant)
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File Type: jpg IMG_1656.JPG (27.5 KB, 97 views)
File Type: jpg IMG_1657.JPG (44.9 KB, 97 views)
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Old 21st February 2011, 12:39 PM   #4
SY is offline SY  United States
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I have some that look like that which are polyester. Very unlikely to be PPS. If you want to sacrifice one, cut out a few pieces of film, ignite them with a cigarette lighter and cautiously sniff. If they go right up, they're definitely not PPS. A sort of sweet smell is characteristic of polyester. A burning candle smell means polypropylene.
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Old 21st February 2011, 12:52 PM   #5
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That are Siemens MKT (polyester) capacitors. Open construction but good sounding. The older ones with greenish sides are MKC (polycarbonate) and those were somewhat better.

One drawback of the open construction is dirt/moisture sensitivy and lead wires that can come off when mechanically treated too rough. They were popular as values could easily be changed by sanding off some material on the upper side. I would not do that but it is possible.

Cap.2 and Cap.4 are silvered-mica caps.
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Last edited by jean-paul; 21st February 2011 at 12:54 PM.
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Old 21st February 2011, 01:06 PM   #6
mjf is offline mjf  Austria
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yes,they look like epcos (=siemens) metallised polyester film capacitors uncoated. series b32560......
rs-components have them in stock.
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Old 22nd February 2011, 09:20 AM   #7
djQUAN is offline djQUAN  Philippines
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I had a few already peeling apart so I tried the burn n' sniff test. kinda reminded me of the smell of drilling/machining acrylic. so I guess it's probably polyester.

thanks for the replies!
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