On Monday, March 28, 2011 5:51:41 PM UTC-7, Arfa Daily wrote:
"whit3rd" wrote in message
...
On Monday, March 28, 2011 4:15:45 AM UTC-7, Mike Tomlinson wrote:
In article
s.com, Sean Hamilton writes

Is it likely that bad solder joints would cause vertical foldover in a
mid-90s CRT television?

Yes, but it's more likely to be a bad cap.

Visual inspection is not enough. You need an ESR meter.

Maybe not; the ESR issues crop up mainly in high-performance
low voltage power supplies

I think you are missing the point of what he was saying regarding ESR. This
parameter is a valid test of the 'goodness' of any electrolytic capacitor,

A test, yes; but not a complete test. The ESR of a 10uF capacitor can be
good, but it won't do the work of a 100 uF capacitor. A combination
of ESR and capacitor-meter testing is better, and a test at the
frequency of interest for ripple reduction is better still.

I wouldn't bother with any of that parameter testing, though.
If you suspect the 10-year-old capacitor, replace it. You'd possibly have to
desolder to test it anyhow, spend the eighty-five cents to put in a new
one.

"whit3rd" wrote in message
...
On Monday, March 28, 2011 5:51:41 PM UTC-7, Arfa Daily wrote:
"whit3rd" wrote in message
...
On Monday, March 28, 2011 4:15:45 AM UTC-7, Mike Tomlinson wrote:
In article

s.com, Sean Hamilton writes

Is it likely that bad solder joints would cause vertical foldover in
a
mid-90s CRT television?

Yes, but it's more likely to be a bad cap.

Visual inspection is not enough. You need an ESR meter.

Maybe not; the ESR issues crop up mainly in high-performance
low voltage power supplies

I think you are missing the point of what he was saying regarding ESR.
This
parameter is a valid test of the 'goodness' of any electrolytic
capacitor,

A test, yes; but not a complete test. The ESR of a 10uF capacitor can be
good, but it won't do the work of a 100 uF capacitor. A combination
of ESR and capacitor-meter testing is better, and a test at the
frequency of interest for ripple reduction is better still.

I wouldn't bother with any of that parameter testing, though.
If you suspect the 10-year-old capacitor, replace it. You'd possibly have
to
desolder to test it anyhow, spend the eighty-five cents to put in a new
one.


I hear what you're saying, and it does, on paper at least, have some
validity. However, my comments are based purely on many many years'
experience of doing service work on electronic equipment, from all walks of
life from consumer through industrial, and on a daily basis. I replace bad
electrolytic caps all the time. Several items every week will require bad
caps finding and replacing, and in just about every single case, the ESR
meter tells the story. In fact, it is probably the most useful test
instrument to live on my bench, and has paid for itself many times over.

Whilst I accept that electrolytics *do* fall in value, I find it actually
quite rare. Almost always, if a cap has fallen in value, its ESR will also
be out of the window. In my experience though, the reverse is often not
true. Having found a bad cap with my ESR meter, I do occasionally check the
value on my digital C meter, and for the most part, find it to be well
within tolerance.

As to having to remove caps to test them, again this is rare, and quite
impractical on complex switchers which may have many electrolytics, and more
than one that is faulty. I don't know if you are personally involved in
commercial service work, but in today's economic climate, and with the low
value of much equipment, the name of the game is quick and accurate
diagnosis of a problem, and minimising additional costs of time and
materials. I have never been an advocate of 'shotgunning' faults by
replacing components which may or may not be faulty. I have had many items
pass across my bench over the years which have come from other service
outfits who have replaced components 'willy-nilly' that they suspected to be
faulty, but without ever getting to the bottom of the original problem, and
having compounded that original fault in their efforts. I have had caps
fitted backwards, diodes and transistors fitted backwards, wrong value
resistors fitted, print damage and so on. So personally, I like to have a
bit more than a suspicion that a component is faulty, before replacing it.
In the case of electrolytics, my ESR meter, for the most part, does that for
me. In saying that, however, I think that I should also say that I fully
accept that the use of an ESR meter is as much black magic as science and,
although it is a useful instrument when used by its instruction manual, for
the professional user, there is also a considerable amount of interpretation
and 'feel' involved. In 'casual' hands, an ESR meter may be little better
than a multimeter for finding bad caps ...

One place where it can fool you is where an electrolytic has gone short
circuit - fairly rare these days, but does happen. In that case, the ESR
meter will of course, give a nice low reading that will, initially at least,
fool you into thinking that the cap is (probably) good.

Arfa