[earplay]

Just when I thought I was beginning to learn a little, I run into the following: a capacitor about half the size of my little finger marked 150 mfd, 50 v. To my newbie mind, this seems like an odd rating. I searched digi-key, among others, and found no film caps with such a rating.   

These are used in a speaker xover.

Any help would be appreciated....   

[mgalusha]

That is an electrolytic capacitor, a 150uF film cap would be very large, like about the size of a soda can... maybe not that big, but big.

[markC]

See? Now your continuing to learn.

[earplay]

Okay, cool. I thought a film cap that size would be very large. What threw me was its shape. It is constructed like an regular film cap. Tubular say, as opposed to cylindrical, and with a lead from the center of each end.

There are three other caps that are smaller. I think they are referred to as "tank caps". To me, those look like commonly seen electrolytics, that is, short, cylindrical and with leads out of one end. Their values are 6.8 mfd and 2.2 mfd, each 50 v. These make sense as film cap values, though they look more like how I expect an electrolytic to appear.

Thanks, Mike   

[srb]

Tubular say, as opposed to cylindrical ...

I think tubular and cylindrical are the same thing!  It is easier to convey the two different orientations as
 
Axial - a lead coming out of the center of each end
 
Radial - both leads coming out of one end
 
Steve

[earplay]

Thanks Steve,

I know axial and radial are accepted terms. Now I know what they mean. Gotta' learn the lingo.

Technically speaking, I think there is a difference in tube and cylinder, not that it applies well to my example. If you think back to solid geometry, a cylinder is a finite, but a tube can be infinite. Now an infinite cap, that would be something!   

mark, I am continuing to learn. Here's one for you: your vs. you're. Now you're continuing to learn.   

Okay, enough of that from me. I think I'm silly from lack of sleep. Someone dart me!

Thanks again to everyone.

[markC]

Yes, you caught my lack of grammer skills there. I actually do know better, but the typing to thinking skills may lack a little.
If your so inclined and if the speaks are of desireable quality, I'd look @ replacing the 6.8 & 2.2 electros with film types.

[earplay]

Mark, thanks for your help. I'm glad you didn't take my remarks personally. I was just being silly. I make lots of typos and grammatical errors, so I was making fun of myself, too. Here's one from my post: difference in vs. difference between.

Here's the thing about caps. Now that I've seen an electro cap in an axial configuration, my naive classification system has broken down. I thought that axial=film, radial=electro.

I don't know how to differentiate them any longer based on their appearance. I suppose I would replace the electros with film caps of the same value. Is that right?

[*Scotty*]

Electrolytic caps are always contained within an aluminum can. The exterior of the can is electrically "hot" so it is covered by a thin shrinkwrap film of plastic.
Here is a radial electrolytic cap

Axial electrolytic cap


Film cap



Hope these images help,notice that there is always an indentation around one end of the electrolytic cap,this helps seal the cap against leakage.
Yes you replace the electrolytic capacitors with the same value film caps.
Scotty

[srb]

Although electrolytic and film capacitors can be either axial or radial case styles, I will agree that you are likely to run into a greater number of electrolytics that are radials and films that are axials.
 
Here is a nicely organized tutorial on capacitors:
http://www.electronics-tutorials.ws/capacitor/cap_1.html
 
Steve

[earplay]

Ahh! I am making progress.

Tomorrow, when the light is good enough, I'm going to post a picture of the cap that prompted my initial post. It's the radial electrolytic cap. There is no visible indentation around one end. When I reflect, it was the lack of an indentation along with the axial conformation of the cap led me to think it was a film cap.

So, axial construction, no indentation, but an electrolytic as the value and only the value indicates. Pics to follow.

[earplay]

Steve, thanks.

I was going to post a pic, but it isn't really necessary now. The reason is that the cap in question is crimped on both ends. How could I missremember (Thanks, George) two crimps.

Anyhow, this cap is axial and it is crimped on both ends. It is also about twice as long, proportionately, as the cap in your second picture so the proportions are more like film caps I am accustomed to seeing.

Thank you, everyone, for the help and good humor. I've been schooled!   

[avahifi]

Does your mystery capacitor have a polarity marking?  Some kind of marking to indicate either a plus or minus end?  If so it is an electrolytic.  If it is an electrolytic, you must use caution in replacing it with a different electrolytic (or tantalum capacitor).  These MUST be installed with the + and - ends in the correct orientation for that particular circuit or they will go BANG smoke when you turn the unit back on.

There are some non-polar or bi-polar electrolytics used in some special applications that are not polarity sensitive.  They will usually be marked NP or BP and will not have + and - markings.

Regards,

Frank Van Alstine

[earplay]

Thanks, Frank, I did not realize that. I am going to read about resistors today.

It's marked NP, so non-polarized.

Here's a question: can I replace a wirewound resistor with a film resistor of the same value? The resistors in question are 5v.

Also, because I have three wirewound resistors in series. Is it okay to replace their summed ohm values with a single resistor of the summed value?

[srb]

Also, because I have three wirewound resistors in series. Is it okay to replace their summed ohm values with a single resistor of the summed value?

When resistors are in series, the power rating is summed as well as the resistance value.  I suppose you could replace them with a single resistor if the summed value of the resistance and the summed value of the power rating were the same.
 
But it does bring up the question why multiple series resistors were used.  Was it because the manufacturer simply had the resistors in stock and used them up by combining them in series, or because the required resistance value and/or power rating was not easily obtainable in a single high power resistor?
 
It might have also been a physical size requirement, and stacking 3 of them took up less crossover board real estate than a much larger single one.
 
Steve

[earplay]

All the specific components I refer to are in a speaker xover. They are the satellite speakers of a Cambridge Soundworks Ensemble system. The system includes seperate woofers. I am using the satellite speakers as near-field computer speakers driven by a t-amp. I wouldn't be going thru all this if they didn't sound as well as they do. It is also an instructional experience for me. I will be keeping the parts I replace because what I do may be detrimental to the speakers' SQ.

Upon closer examination, there are two resistors in series.

I wouldn't be posting so many of these newbie questions, but I have not yet found a hifi group in my area. Tomorrow, I'm going to try a different tack in that search.