MKP caps: are these for real?

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taj

taj

diyAudio Member
Joined 2005
I just bought some .1uF/250v caps off eBay from a guy in China. I'm a bit suspicious of their dielectric being metallized polypropylene as claimed. Based on their size, they seem much more likely to be metallized polyester.

Here's a photo of a .1uF/50v Panasonic ECQ-P metallized pp cap. (the large one on the left with the crimped leads); and then a Seacor .1uF/250v (the blue one) which I thought was already suspiciously small, and the new one from China is the orange one in the middle.

But technology and manufacturing isn't static so who knows. Anyone care to comment on the probability these are really MKP?

Thanks,

-- Todd
 

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Geek

Geek

Member
Joined 2004
Hi,

Lee's Electronics in Vancouver sells ones that look like those as PP. I did the "Steve Bench linearity test" on them and the curve was a perfect line, despite 0-12V DC bias :)

How long they will last, who knows? :whazzat:

Bottom line is... THEY AIN'T ORANGE DROPS LADDY! :D
 
taj

taj

diyAudio Member
Joined 2005
Magura said:
Sorry I handed you a simple and bulletproof solution that didn't require any special instruments or tools....It won't happen again.

Please continue the wild guessing for the next few pages, as if I had never posted in this thread :whazzat:
Magura
Click to expand...


Hey, I wasn't mocking you or your solution, Magura. I was just trying to be funny. (It won't happen again.) I fully intend to try your test.

But what does polyester smell like?

..Todd
 
KP11520

KP11520

Member
Joined 2007
Hi Magura,

Please forgive us! I know I wasn't making fun of your method, just the silly responses.

Listen, with many of us having to to use eBay and/or China for components for price and/or availability, methods like yours may be the only way to know if we are getting ripped off. (Who really has the equipment to test if these all have the qulality/values that are represented)! I only hope they aren't expensive. Wima MKP4 and 10s are more than I want to burn ( I don't have much experience on pricing on these PP types).

Honestly, I have to say, I won't forget what you said.

I have been bidding (and losing) on OPA627APs and wonder what I'll get if I do win them!

Thank you for the information. I appreciate learning anything that will help my education here with DIY projects!

BTW, Conrad, you are always such a gentleman. Thanks for setting a fine example!

Regards//Keith
 
Magura

Magura

Member
Joined 2003
class-a-labs.com
taj said:



Hey, I wasn't mocking you or your solution, Magura. I was just trying to be funny. (It won't happen again.) I fully intend to try your test.

But what does polyester smell like?

..Todd
Click to expand...


Ok, my mistake :)

The smell of polyester is hard to describe, but it's quite far from that of polypropylene. The only other possibility there is theese days would be polystyrene, and it smells a bit like gasoline....so if it doesn't smell like candles or gasoline....you got yourself a polyester cap.

Magura :)
 
taj

taj

diyAudio Member
Joined 2005
Conrad Hoffman said:
The easy non-destructive method is to put them on a capacitance bridge and see what the DF number is. Polypropylene will approach, but typically not equal, polystyrene, whereas polyester (Mylar) will be somewhat higher then either of those two. Or, get a match...
Click to expand...


Hi Conrad,

I did read your webpage, so I know what DF is, but I still haven't researched capacitance bridges, so without knowing what that is, it doesn't sound very easy. :)

Besides, I come from the Myth Busters school of testing things. I like to burn things and blow them up just to see what they smell like under adverse conditions. :devilr:

..Todd
 
C

Conrad Hoffman

Member
Joined 2007
conradhoffman.com
I'm probably a bit daft in the head, because as a child I inhaled the sweet smell of burning selenium rectifiers. Nothing quite like 'em. We won't even talk about the mercury experiments. Anyway, if you want to test small value capacitors, it's really easier than you might think to throw together a capacitance bridge. Even if it doesn't read out directly, you can just measure a couple resistances and calculate both capacitance and dissipation factor. It's the 21st century, we have computers and Excel, so this stuff is easy now. You will, however, need a signal source and a meter or scope or headphones. PM me if you're interested.
 
Geek

Geek

Member
Joined 2004
Conrad Hoffman said:
I'm probably a bit daft in the head, because as a child I inhaled the sweet smell of burning selenium rectifiers. Nothing quite like 'em. We won't even talk about the mercury experiments.
Click to expand...

And you'll/have outlive(d) several athletic classmates?


QSerraTico_Tico said:
Heat them up with a hair-dryer while measuring capacitance...
Click to expand...

Ooooh, gotta try that :)
 
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