Capacitor question

HellasTechn · Oct 25, 2016

Hello friends !

I would like to ask about this capacitor. I have seen such in old telephone sets and in switching PSU's. What kind of caps are they and what are they mainly used for (audio applications?) ? Also how can we read it's value ? Is it the same way we read ceramics ?

Thank you !

HellasTechn · Oct 25, 2016

Ok i think i found all i need here :
http://tronixstuff.com/2010/06/04/electronic-components-the-capacitor/

but still,

Is there some guide about which kind of capacitor is better for a cpecific application ?

For example, which is better for audio filtering, which is better for decoupling etc.

davenn · Oct 25, 2016

HellasTechn said:

Is there some guide about which kind of capacitor is better for a cpecific application ?

For example, which is better for audio filtering, which is better for decoupling etc.
Click to expand...

the basics of that is answered in the link you gave .... keep reading

Dave

HellasTechn · Oct 25, 2016

So 1 cap lead to the Mains ac socket (line) and the other lead to say red probe of DMM and then the black of the DMM to neutral of the Mains socket ? and then reverse the cap and read again ?

HellasTechn · Oct 25, 2016

davenn said:

the basics of that is answered in the link you gave .... keep reading
Click to expand...

I have. For theese specific caps they say this
"These are also very popular for high-frequency circuits,"

so ? what are they good for ? Serving as HF filters ?

davenn · Oct 25, 2016

HellasTechn said:

I have. For theese specific caps they say this
"These are also very popular for high-frequency circuits,"

so ? what are they good for ? Serving as HF filters ?
Click to expand...

for those "greencaps" their common nickname for obvious reasons, audio use, definitely wouldn't use them for RF

davenn · Oct 25, 2016

HellasTechn said:

So 1 cap lead to the Mains ac socket (line) and the other lead to say red probe of DMM and then the black of the DMM to neutral of the Mains socket ? and then reverse the cap and read again ?
Click to expand...

NO, NO, NOOOOOOOOOO

Edd did say gnd socket ................... but still very dangerous advice, I have deleted his post and edit it out of your post
don't ever go near trying

HellasTechn · Oct 27, 2016

Please go ahead and delete my post #4 and this one. Better be on the safe side.

HellasTechn · Oct 27, 2016

davenn said:

for those "greencaps" their common nickname for obvious reasons, audio use, definitely wouldn't use them for RF
Click to expand...

See ?
This is what i am talking about, while this site states they are popular at high freq circuits, you say not for RF.

While i have very limited gnowledge on electronics it is not easy for me to understand what they are best used for.
And then i ask is there something like a guide thet someone like me can look and quickly figure out what kind of cap to use in some circuit ?

For example i know that for smoothing we use electrolytics.

HellasTechn · Oct 27, 2016

davenn said:

for those "greencaps" their common nickname for obvious reasons,
Click to expand...

Is "Greencap" their nickname ? i dont know how that relates to audio but please, please don't take me wrong it may very well be my poor skill in english (some idiom i am not aware of).

Arouse1973 · Oct 27, 2016

It looks like a Mylar film cap to me, might be wrong. If it is then they are classed as general purpose caps normally for DC and can be made to withstand very high voltages. They can have large losses in AC circuits at high temperatures.
Thanks
Adam

davenn · Oct 27, 2016

HellasTechn said:

Is "Greencap" their nickname ?
Click to expand...

davenn said:

for those "greencaps" their common nickname for obvious reasons,
Click to expand...

HellasTechn said:

This is what i am talking about, while this site states they are popular at high freq circuits, you say not for RF.
Click to expand...

I wouldn't use them (and you will never see them in signal paths of HF (high freq and up) circuits) in RF circuits over a MHz or two, they are not stable enough

HellasTechn said:

For example i know that for smoothing we use electrolytics.
Click to expand...

yes and also commonly used in audio circuits as interstage coupling of the signal ... between inputs and preamps, then between preamp and power amp stages

HellasTechn said:

Also how can we read it's value ? Is it the same way we read ceramics ?
Click to expand...

That was sorta answered in that link.....

capacitors are marked in 5 common ways

1) the direct uF value 100uF, 1uF, 0.1 uF etc

2) indirect uF way, by showing a decimal value, .1, .001 etc ( the leading zero is commonly dropped to save space
if you see a cap with .1 on it, IT WILL be 0.1 uF

3) the 3 digit code, saves lots of space, 106, 104, 103, 102, 683 etc = 10uF, 0.1uF, 0.01uF, 0.001uF, 0.068uF = (68nF / 68000pF)

4) any ceramic, mylar, polyprop, polyester cap marked in whole numbers eg 10, 1000, 2200 is a pF value eg 2200 = 2200pF

5) not really seen any more but really old tubular caps and some very small caps during 70's and '80's used colour banding like resistors

an example was in another thread over the last couple of days .....

you can see the lower one has spewed its guts and let out the "magic smoke"

Dave

davenn · Oct 27, 2016

a nice chart I just found

Dave

davenn · Oct 27, 2016

HellasTechn said:

While i have very limited gnowledge on electronics it is not easy for me to understand what they are best used for.
And then i ask is there something like a guide thet someone like me can look and quickly figure out what kind of cap to use in some circuit ?
Click to expand...

you would do well to read the section in the wiki entry, about 1/2 way down the page

https://en.wikipedia.org/wiki/Capacitor_types

Comparison of types an extensive table of types, their make up, uses and disadvantages

davenn · Oct 27, 2016

Arouse1973 said:

It looks like a Mylar film cap to me, might be wrong.
Click to expand...

no, greencaps are definitely polyester

Arouse1973 · Oct 28, 2016

davenn said:

no, greencaps are definitely polyester
Click to expand...

So are Mylar film and Mylar polyester
Adam

Arouse1973 · Oct 28, 2016

Further investigation reveals that Mylar is a trade name and is in fact PET a form of polyester, but there are more than one type of polyester
Adam

Capacitor question

HellasTechn

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