Meat Plow wrote:

On Mon, 17 Aug 2009 06:22:49 -0700, D Yuniskis
wrote:

Hi,

[Apologies if this appears as a repost -- it hasn't
shown up on my server in the better part of a day]

I've been repairing lots of "defective" LCD monitors
for a local non-profit. Of course, many boil down to
bad electrolytics from those notorious Taiwanese
manufacturers.

[I'd like to avoid rehashing that subject as I am sure
there's nothing *new* that anyone can add -- and, it's
not the nature of my question, here!]

What I would like to know is which circuit topologies
tend to aggravate this problem. From my casual
observations (I've done most of my repairs without
the benefit of any design documentation), the failing
components either seem to be proximate to heat sources
*or* in configurations where they see high ripple
currents (suggesting this is a problem with the
devices' ESR -- internal heating).

My observations come from a few *hundred* samples
from different manufacturers, different models,
different subassembly manufacturers, etc.

Does anyone have any *definitive* answers about this?
And, long-term remedies? (i.e., does replacement with
a good, high temp, low ESR cap *solve* the problem or
just kick it down the road?)

Are there lessons to be learned when *designing* these
types of circuit topologies to avoid these failure
modes? (besides picking good vendors)

So the caps should be moved to a cooler location?


Not a good idea. The added inductance and resistance of the leads
will cause problems. Why bother with low ESR electrolytics if you make
them useless?


--
You can't have a sense of humor, if you have no sense!