Resistor types

[mindwave_21]

Hey all, I was just wondering how you can tell the difference between carbon film, carbon comp, and metal film resistors.  Also, what are the visible differences between film caps (metal film?) versus tantalum caps?
Thanks

[Peter Snowberg]

For the bulk of resistors it's pretty easy to tell by appearance.


Carbon comps are very cylindrical and usually darker brown. You'll usually see three colored bands and a fourth tolerance band.



Carbon films are cylindrical, but they have "caps" on the ends (under the epoxy coating) that connect to the leads so often they're skinnier in the middle than the ends. The color is most often more of a tan or light tan. You'll see three colored bands and a fourth tolerance band.



Metal films look like carbon films, but they're usually a different color like blue (most often) or green, and they have four colored bands with a fifth band for tolerance. The extra band is the give away there.



Most tantalum caps looks like epoxy covered frozen rain drops for lack of a better explanation.



Most common mylar caps look like a piece of "chicklet" gum. They're more like rounded rectangles than drops. Other type of films are often a bit fatter.


The best suggestion I could make would be to scan through catalogs that have pictures. Film caps in particular come in a zillion different appearances. There are a whole bunch of different type of films too.... each one looks different.

I hope that helps.

Take care,
-Peter

[niftydog]

Different resistors may look the same, but they have different tolerances.  This is generally the major visible difference between the types you've mentioned.  There are no hard and fast rules about resistor colours, but in very general terms metal films are blue or green and carbon films are a sort of light beige colour.

Carbon comps are old school, and have large tolerances (±10%)
Carbon films are middle school, and have medium tolerances (±5%)
Metal films are new school and have small tolerances (±1%)

What's that I hear you say?  Tolerances?  Keh?  Suss it out by futzing with this cool web-tool.

"metal film" capacitors are more correctly called "metallized polyester/polypropylene film" capacitors.  For my money, calling them metal film just confuses them with resistors!  Often, the "metallized" bit is left off.

Generally, small capacitance, high voltage beasts used in audio speaker crossover networks and other high current applications.  Buckets of capacitor info here and here.  They can be low tolerance, but the common ones are ±5% or ±10%.

Tantalums are interesting beasts, they look like little blobs of plastic (see below).  They are more stable over time than electrolytics, particularly at higher frequencies.  They have less ESR, they're smaller, tolerate higher temperatures stay close to their specified capacitance.  They are sometimes called "dipped" caps, and they are very similar to "solid aluminium" caps.

Check out this table for a quick comparison of caps.

...and, from this sites FAQ section (see link above) a piccy of some different types.




Google is your friend, my friend...

[bobbletrox]

I've got a bit of a component fetish I'm afraid.  I've been through the "use rediculously large metalized film capacitors" stage...and now I think I'm heading in a "everything Ceramic caps and carbon film resistors" stage.

It's quite sad really.

[Peter Snowberg]

...and now I think I'm heading in a "everything Ceramic caps and carbon film resistors" stage.

It's quite sad really.

Don't worry... it's just a phase. You will soon grow tired of the noise and microphonics. (or you may just love that vintage mojo)

The experience will be helpful and it will allow you to decide what flavor components you want to play with next month.

I've gone through many phases and now I'm in the metal film/cheap mylar/silver-mica/expensive opamp phase. I'm liking it very much.

Take care,
-Peter

[Paul Perry (Frostwave)]

You will soon grow tired of the noise and microphonics.

I saw an "auto stethoscope" DIY articlke once, for listening to car engine noises, where the pickup was a ceramic bypass cap glued to the end of a metal rod!! I would recommend those suprisingly small "high-K" 0.1 bypass caps for that..

[bobbletrox]

Don't worry... it's just a phase. You will soon grow tired of the noise and microphonics. (or you may just love that vintage mojo)

The experience will be helpful and it will allow you to decide what flavor components you want to play with next month.

I've gone through many phases and now I'm in the metal film/cheap mylar/silver-mica/expensive opamp phase. I'm liking it very much.

Take care,
-Peter

lol...well I'm going to try it out in doug deeper's Garage Fuzz this weekend.  Add a couple of 2n2222a's into the mix and I'll be on the way to noise-city...er...I mean "vintage mojo-town".

[mindwave_21]

Wow, thanks for the info everyone!  Looking to build my first pedal within the next 2 or 3 weeks.  I'll fill you guys in!