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old nomenclature for capacitance

M

Martin Baker

Jan 1, 1970
0
Dear Group,
I am trying to help restore an old amplifier, and we have a
schematic, but it shows capacitances in mmf. If I were to guess, I
would probably think it meant millmicrofarads, or nanofarads, but it
could mean something entirely different.

Does anyon know exactly what a mmf is?

Thanks in advance,

Martin
 
M

Michael Black

Jan 1, 1970
0
Martin said:
Dear Group,
I am trying to help restore an old amplifier, and we have a
schematic, but it shows capacitances in mmf. If I were to guess, I
would probably think it meant millmicrofarads, or nanofarads, but it
could mean something entirely different.

Does anyon know exactly what a mmf is?

Thanks in advance,

Martin


It's "micro-micro-farad". I have no idea where the terminology
originated, but it's the same thing as pF. So 10uuF is 10pF.

Michael
 
D

DarkMatter

Jan 1, 1970
0
It's "micro-micro-farad". I have no idea where the terminology
originated, but it's the same thing as pF. So 10uuF is 10pF.


If this is true, that particular cap would be in quite a small
package.

If he is referring to designations on an electrolytic cap, then your
assessment must be incorrect. I do not know of any picofarad
electrolytics.
 
M

Michael Black

Jan 1, 1970
0
DarkMatter said:
If this is true, that particular cap would be in quite a small
package.

If he is referring to designations on an electrolytic cap, then your
assessment must be incorrect. I do not know of any picofarad
electrolytics.

You've just showed your age.

All you have to do is look at any book beyond a certain age, and
you will see uuF used for pF.

I just pulled one out, from 1958, and I opened it at random.
Right away, a 28 to 50Mc oscillator. A 75uuF variable. The feedback
capacitor is 10uuF. There is no way those are electrolytic.

Clearly, either they are small capacitors, feedback capacitors maybe,
or the original schematic is at fault.

I wasn't guessing; the useage fell out of favor in the early sixties,
which was before my time, but in any of the old books I collected
thirty years ago it was a common useage.

You aren't familiar with the term, yet you dismiss my explanation
because it isn't what you expect.

Michael
 
R

Rich Grise

Jan 1, 1970
0
Yes they're micromicrofarads, but that's a picofarad.
A nanofarad is a millimicrofarad.

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
It's because it wasn't until the early '60s or whatever
that the term "picofarad" was invented.

I remember looking at one of the Heathkit scopes from
that era and wondering "what the hell is a nsec?" Then
we found out that it was "nano-," and of course, they
immediately became bananaseconds. %-}

cheers!
Rich
 
J

Joe McElvenney

Jan 1, 1970
0
Hi,

Back when Roosevelt ruled the roost, some American schematics
used 'M' for 'k', i.e. 10k was marked 10M, and in the 'Admiralty
Handbook of Wireless Telegraphy - 1938' (Royal Navy) all the
capacitances are quoted in 'Jars', which I believe is about 900
pf.

And they're still dreamin' in California about the mmf's and
the pf's :)


Cheers - Joe
 
J

John Larkin

Jan 1, 1970
0
It's because it wasn't until the early '60s or whatever
that the term "picofarad" was invented.

I remember looking at one of the Heathkit scopes from
that era and wondering "what the hell is a nsec?" Then
we found out that it was "nano-," and of course, they
immediately became bananaseconds. %-}

It used to be a millimicrosecond.


John
 
R

Ross Mac

Jan 1, 1970
0
Michael Black said:
You've just showed your age.

All you have to do is look at any book beyond a certain age, and
you will see uuF used for pF.

I just pulled one out, from 1958, and I opened it at random.
Right away, a 28 to 50Mc oscillator. A 75uuF variable. The feedback
capacitor is 10uuF. There is no way those are electrolytic.

Clearly, either they are small capacitors, feedback capacitors maybe,
or the original schematic is at fault.

I wasn't guessing; the useage fell out of favor in the early sixties,
which was before my time, but in any of the old books I collected
thirty years ago it was a common useage.

You aren't familiar with the term, yet you dismiss my explanation
because it isn't what you expect.

Michael
You are correct!...I remember that nomenclature from my early days in the
business....pf was a fairly new entitiy back then.....Happy Holidays....Ross
 
R

Ross Mac

Jan 1, 1970
0
Rich Grise said:
Yes they're micromicrofarads, but that's a picofarad.
A nanofarad is a millimicrofarad.

Cheers!
Rich
That too is correct...it's all about exponential notation...
In the days of the slide rule...it was particularly important...It was the
only way to keep track of the decimal point!
I still have my Pickett stuffed away in a case...Anyone else save their
slide rule out there?......take care, Ross
 
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