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10nF Cap....what is it?

11/15/1998 7:02 AM
Bill Harbour
10nF Cap....what is it?
I've got a schematic with a 10nF cap on it. What does that translate to in the real world? All the caps I've seen are either pico farads or micro farads.  
Bill Harbour
11/15/1998 10:26 AM
Steve W

10nF is 0.01 microfarads.  
Steve W
11/15/1998 10:30 AM

That would be a Nanofarad cap. I've never seen caps marked that way. Usually they are in microfarads (uf or MF) or picofarads (pf).  
uf is 10 to the -6 farads  
pf is 10 to the -12 farads  
nf is right in the middle at 10 to the -9 farads  
so a 10 nf cap would be the same as:  
a 10 000 pf cap  
a .01 uf cap. .01 uf caps are pretty common.  
I wonder why the folks who drew up that schematic notated it that way. Could it be a misprint? What is it a schematic of?  
David Becker.
11/15/1998 10:23 PM

They are in mostly English amps,Marshalls,Sound Citys,and others.
11/16/1998 6:07 AM

I wonder why the folks who drew up that schematic notated it that way. Could it be a misprint? What is it a schematic of?  
I have noticed that European schematics use nanofarads a lot. Also, our engineers at work like to use that term also. They think 10nF looks better and is less confusing than 0.01uF, kind of like how 1M is less confusing than 1000K. Also, a lot of new caps between 0.001uF and 1uF are marked in nF. I checked a few preamp caps out of a Marshall I once had, they were marked in nF, such as 680nF instead of 0.68uF.
11/16/1998 6:52 AM

It is very easy to misread a figure that starts with a decimal point. A dirt speck on the photocopyer glass can create one that wasn't there, and other times it may not be reproduced clearly, especially with schematics being more complicated and trying to cram so much information on one page.  
We were always taught for engineering calculations to start a decimal number that had no figures left of the decimal point with a zero. That way, the decimal point would have a better chance of not getting missed. These days, no one wants to write anything extra, because it slows them down and takes up more space.  
Resistor codes have been modified to get rid of the decimal point. For instance, a 1.5k resistor would be noted on a current electronic drawing as 1K5. The K goes in the location of the decimal point. If the value is a whole number, greater than 1K, then the K goes at the end, such as 220K. If the resistor's value is less than 1K, rather than use a decimal fraction of 1000 they denote it with R. A 2.2 ohm resistor would be marked 2R2. So using a convention like this, there's only one place the decimal point could go, but it's not shown.  
So they are doing a similar thing with capacitors. There are so many capacitors in common audio circuits with values between picofarads and microfarads, all using decimal points at the beginning of the number. So the nanofarad is becoming used much more frequently. I guess they're trying to use figures with no more than 3 digits, and the number never starts with a decimal point.  
Those familiar with circuits get a feel for what size range a particular coupling capacitor, etc., should be in anyway. It's going to take me a while before I can just look at a nanofarad value and not have to stop & mentally convert into a microfarad or picofarad value that immediately makes sense to me.
11/16/1998 10:49 AM

I had noticed the use of 1k5 and the like that in some of the more recent schematics I have gotten ahold of and thought it was a good idea indeed. I don't have to do much component level troubleshooting in the field but when I do it invaribly involves being in a cramped dark space reading a blurry schematic with a flash light in my mouth!  
I'd never seen a cap in nanofarads before but that is probably because at work everything I work on is from a US source (millitary) and my hobby worked hasn't involved British amps yet. It makes sense to notate things that way. Especially in circuits OTHER than audio where you don't have the same values all the time and you can't always make a SWAG about what it should be.  

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