Michael Kennedy said:
Is there any good way at guessing what the cap might be by checking the
esr of nearby similar caps?
- Mike
As in Andy's post "Re: SMD Cap problem", testing in-circuit isn't
necessarily as accurate or reliable as testing out-of-circuit.
Bad ESR isn't generally a big problem with ceramic caps, SMD or not. A good
ESR on a cap out-of-circuit doesn't mean the cap _value_ is correct, either,
and the value determines circuit behavior, especially important in tuned
circuits.
I'm afraid the only reliable way to test unmarked caps is to remove them
from the board and compare what your test equipment says to manufacturer
data (or a working unit's removed caps). You can often narrow down the
search for bad parts where there is no schematic available by comparing
voltage and resistance readings with those of a working unit.
I'm curious, these being such tiny components and often in close proximity
to other components, how exactly did u determine a particular cap or patch
of caps is thermally intermittent? Could it be that you've heated up (or
chilled) nearby parts as well and it's _those_ parts that caused the results
u attribute to the ceramic caps?