Name that cap...

Gordon JC Pearce gordon at
Fri Mar 11 09:35:56 CST 2005

Bill Sudbrink wrote:

> You want to look at "Figure #3".  I've used several different image
> processing
> programs, but I can't get the scribble next to the cap legible.  I've looked
> at the data sheet for the chip, but I don't know enough for an obvious value
> to jump out at me.  Part of the accompanying text says: "The RC time
> constant
> is adjusted to give an output pulse width on pin#1 of the 74LS121 of 5.5
> ls."
> I assume "ls" is an oddball abbreviation for microsecond?

Well - the spec for the LS121 is pretty well-known.  Someone with more 
caffeine and inclination than I might well look up the datasheet and 
work out what the value ought to be.  It looks like it says "270" 
overscribbled with "220" to me - what units I don't know.  Try 220nF. 
If that doesn't work, try 220pF.  You'll be in the ballpark with one of 

Then, y'see, the phrase is "select on test".


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