"Andrew Gabriel" wrote in message
...
In article ,
"Dave Plowman (News)" writes:
In article ,
Andrew Gabriel wrote:
In article ,
Jules Richardson writes:

I seem to be accumulating a pile of things with faults that are most
likely down to dodgy capacitors, but my homebrew ESR meter's one of
those things that is still in deep storage back in the UK. So...

I repair lots of things, but I haven't yet needed an ESR meter. To test,
I simply parallel up a new capacitor, and see if that fixes the issue.

Not much use with tantalum which can fail short circuit. ;-)

Checking a suspect cap with an ESR meter is so much quicker than by
substitution, etc. I'd say it's one of those things you may not miss if
you've never had one.

I didn't say by substitution - I usually just touch the leads of a new
one against the existing one's leads. If it's a mains circuit, I might
temporarily solder it to the existing cap's solder pads on the underside
of the circuit board so I'm not holding it.

As Dave says with tants, that's all very well unless the cap has gone short.
Whilst I know it's not definitive, the fact that a decent ESR meter is also
a low ohms meter, if you hang it across a 47uF cap, and see a reading of
0.02 ohms, there's a very good chance that it is short circuit, and not just
an exceptionally good cap, ESR-wise. A quick dab across the legs with a good
old AVO, then confirms this. About the only thing that I would say about
using an ESR meter, is that a degree of experience with them has to be built
up. That's how you would know, for instance, that a reading of 0.02 ohms for
a 47uF cap would be wrong, but could well be right for a decent 10000uF cap.
Each to his own, I guess, but I don't think I have ever come across an
engineer that hasn't sworn by his ESR meter, once he's actually been out and
got one, and put it to commercial use. If anything happened to mine, it
would be like cutting my arm off ...

Arfa



My Bob Parker kit one was pretty expensive, but still paid for itself.
They're a lot cheaper now with even cheaper alternatives.

--
Andrew Gabriel
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