Surface Mount Components

[Garfield Willis]

On Sun, 24 Sep 2000 22:22:53 -0500, "J. Creech" <jcreech1 at olemac.net>
wrote:

>There are 2 seperate surface-mount capacitors that are a little on the
>toasty side, I believe from being mounted across the same bus as the worst
>of the electrolytic caps. I want to replace these when I perform the repair.
>The hitch is this: they're unmarked.
>...
> My question is, how are these things identified? Both of them are the same
>color (kinda medium brown) and the same size. There are also others on the
>board that look identical to them, as well as others that are different
>colors, sizes, etc. Can I safely assume that all the ones of the same
>size/color are the same value (within a certain tolerance)? Can I use other
>S.M. components (off of other techno-debris I have laying around) that are
>same size/color?

Not really. That medium tan color is from the particular dielectric
material that's used on the most common surface mount Cs, and it has
nuthin tado with the value. Most SM C's aren't marked at all for value
or V spec. The best thing to do is to see if you can isolate the
device (ya know, one lead/trace/side open), and MEASURE the C with a
meter that can do so. If they're toast to the point where you cain't
measure them, well then you're toast too! If you can get a decent
measurement that looks right, but their metal ends are eaten by
corrosion, then replace with same value.

Bout all I can think to suggest. Things are getting so small now that
the ID marks are all disappearing from components. Many SM R's still
have marks, but C's usually have nothing, and many SM ICs have nothing
but a "package ID" number that you must have the mfg's cross-reference
for, in order to ident the part. Rapidly approaching the "black-box"
state.

HTH,
Gar


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