What kind of capacitors are these ?

Somebody took a major tumble on those. They are multilayer stacked film types, probably polyester and about as hermetic as my arse after four vindaloos and eighteen pints of Guiness. Look at the lead connections, they are basically 'soldered' into the schoop layer and totally exposed. No glass encapsulation at all. Might be worth 5C a piece.

The manufacturer is probably Siemens.

DNA

"Dave Moore"

** Same type as these:

** Stacked film polyester, general purpose.

Small but fragile, IME.

NOT glass in any way.

........ Phil

Clear epoxy. European-style stacked-film caps. Siemens had them first, AFAIR, and I think Philips followed. Panasonic has some with a brown epoxy dip.

The stacked-film construction is low inductance, and they had relatively high capacitance per unit volume, and the low leakage you expect of a good film cap.

I made a PID controller with something like a 60 minute Ti using two

2.2uF specimens and some CMOS op-amps back years ago.

Best regards, Spehro Pefhany

--
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No, they're Siemens stacked polyester types and very old.

Graham

I'm mildly astonished that they're still in production.

Certainly not.

Graham

For a bit of fun I emailed the buyer and seller with the good news ! ;-)

Graham

Yeah, good film caps have pretty low leakage. I charged up a couple polyester and a couple polypropylene 0.1uF ~100V rated caps a few years ago, to about 12V. Last time I measured them, the polyesters were showing a self-discharge time constant in excess of 5 years, and the polyprops' time constant was in excess of 50 years, at room temperature. It's been a few years since I measured them now, and I should see if I can set up to do that again. Gotta be careful to not disturb them too much with the measurement.

Cheers, Tom

Spehro Pefhany wrote:

I think they were polycarbonate (low TC). I used them around

1975 and got bitten by moisture absorption affecting the value. Siemens did a version later that was epoxy encapsulated to fix the problem, but at significantly higher cost.

Regards Ian

Sure about that ? They certainly do a polyester cap like that but these days the case colour isn't green but clear.

I wondered if that was going to be a problem. I've always avoided them.

With epoxy over the ends ? I've seen a few of them.

Graham

Actually, the older green ones were polycarbonate (aka 'mylar'), with a little different flammability. The ones pictured at Farnell are polyester.

I don't think the seller has gotten very close to the parts being sold, or maybe he's been mislead by the thickness of the outer stack layer 'stiffener' on these older parts. Easy enough to disassemble, if he wee so inclined.

There are glass-encapsulated ceramic capacitors and porcelain/ceramic dielectric capacitors that might be considered as a type of glass cap.

RL

Mylar is polyester not polycarbonate. Mylar is simply DuPont's trade name.

polyester.

My recollection is that Siemens simply changed the colour of the outer for no good reason and they've always been polyester. I've certainly seen / used them in the distant past - read 1970s - and I certainly wouldn't have bought any polycaronate types on account of cost.

Graham

"legg" "Phil Allison"

** Nonsense - Mylar IS polyester !!

....... Phil

;-)

"Interfering with an auction" ...tut...tut... That is not allowed.

Specifically, e-mailing the buyer is prohibited, even on a completed auction:

"Members are not permitted to email buyers in an open or completed transaction to warn them away from a seller or item" ...

Violations of this policy may result in a range of actions, including: Listing cancellation Limits on account privileges Account suspension Forfeit of eBay fees on cancelled listings Loss of PowerSeller status

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Strange if the item description is clearly incorrect.

In which case one could easily open up a throwaway account and get away with it !

Graham

No. Mylar is polyetheleneterphthalate, "PET", used in magnetic tapes and soda bottles. A lot of those stacked plastic film capacitors were polystyrene and polypropropylene.

--
JosephKK
Gegen dummheit kampfen die Gotter Selbst, vergebens.  
--Schiller

** And " polyetheleneterephthalate " IS called " polyester " in the electronics industry & elsewhere.

Go look it up on Google - you DAMNED HALF WIT !!!!

......... Phil

Mylar == Polyethylene terephthalate (PET) == polyester

Got any links to any such thing?

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com