stupid question

[Valvehead]

Ive got yet another old amp project - a Stromberg carlson amp. Im re-capping it and I have a question.

there are 2 small black disc caps in it.

the scem shows them as --l(--

and it says 680 UUF and 100 UUF on the scem . On the caps it just says 680 and 100 .

ive never seen UUF.....what is UUF ? its not microfarad is it ??

and they appear to be just ceramic disc caps with no polarity markings

[loudthud]

UUF is micro micro farad. Today we call them Pico Farads.

[Valvehead]

ahh. ok

so they are simply 680pf and 100pf disc caps

[Enzo]

yes.

uuf is the more recent form, (but still before pico came into common use.) while even older schematics used mmf.

[Chuck H]

Sweet! I'm sort of a tweener when it comes to old and "less old" terminologies. I've always managed to work it out by looking at the value in context to the circuit!?! But it's fun to see someone asking about it. Truly modern terminologies can be downright confounded at times too. If you can't look at the circuit and take the value designation in context you could be surfing the information super highway. I call it the information pile because there's so much BS and opinion to dig through before you find any bones with meat on them.

[Enzo]

"m" for "micro" was the old way, so mf meant microfarad, and mmf meant micro-microfarad. micro-micro is the same as pico. The term pico existed back then, but no one used it. it would have been high-falutin'. Later they switched over to the u we know today, except it really is not a "u", it is a lower case, Greek letter "mu". (And mu was their m)

Old ham radio guys used to use the term "mickey mouse" for mm when reading the mmf character. As in, "I installed a 20 mickey mouse cap on my plate to cure those parasitics."

In the old tube days, a whole farad was a concept, but not a reality. A one farad cap would have been the size of your garage. But today, you can find 1 farad caps in car stereo rigs. And even small 5 farad caps used as backup batteries for memory in some circuits. SO a millifarad, 1/1000 of a farad, is a reasonable thing to expect somewhere. Today "mf" would mean millifarad, rather than microfarad.


Also, "M" was used to mean 1000 sometimes. Seems to me I mainly see it in very old Gibson drawings, but here and there also. Today we use M for mega as in million. But you'd see an amp drawing with a 500M volume control and a 1.5M cathode resistor. Those are 500,000 pots, not 500 meg.