On looking at past postings I see that Roman Black doesn't seem to have
posted on PICLIst since January !!!
Time to send out a posse methinks!

Summary:
The Electronics Australia ESR meter (kitset) as enthusiastically recommended
by Roman Black is utterly
brilliant at locating old dry electrolytic capacitors in circuit.
It also has many other uses.
Buy one!

(I consider mine has about paid for itself after one use).

"K7204 EA 1/96 ESR & Low Ohms Meter"
_____________________


This post is to recommend an instrument that Roman recommended.
It's an in circuit ESR & low ohms tester available in kitset form & based on
an Electronics Australia article.
While its specialist purpose is to perform Equivalent series Resistance
tests
on electrolytic capacitors in-circuit, it can also be used as a general
purpose low ohms tester.

Preamble: Electrolytic capacitors have a common failure mode caused by loss
of electrolyte. This can occur with age or earlier on if run at a high
temperature. The result is an increase in the effective resistance for AC
signals. The capacitor can lose its effective filtering capability while
still retaining its capacitance (as measured on a capacitance tester) and
still having low leakage. Without an ESR meter such failures are essentially
undetectable. Such failures are common in electronic equipment and indeed
may be the major cause of failures.

We have an oldish and very heavy 29" AWA brand television. Over time it
slowly ceases turning on reliably via remote control and after enough time
it won't turn on at all by any means. On a previous occasion I searched for
the problem
to no avail and finally summoned up enough muscle and will power to lug it
to the local TV repairer. They (presumably having inside knowledge) replaced
several small capacitors and it
again worked OK. The problem returned some years later and as there was
another unrelated fault I again sent it to the repairers. This time the fix
was partial and the problem returned rapidly.

Lack of the TV's circuits, general inexperience with TV circuitry and best
use of time was weighed
against , decreasing muscle power and increasing annoyance
at paying repairers for a poor job - I decided to take up Roman Black's
highly recommended solution of the EA ESR meter. Construction would take a
long evening in front of the TV (where else? :-) ).

Note that this is an *** ESR meter *** and NOT just a low ohms meter. It
uses AC measurement techniques and uses a low enough signal to allow in
circuit testing.

Using the meter to look in the general area where I expected the fault to
lie produced success with the second capacitor tested. It had a very very
high ESR reading compared to the values provided with the meter (on it's
front panel). One replacement 100 uF 25V cap and the TV appears to be back
to full working order. I could have found the fault with a scorched-earth
capacitor replacement policy. Replacing caps on a tight TV PCB is at best
annoying, requires a range of suitable caps to hand, may cause extra
problems and takes time. And it may have been something else. This meter
allows
intelligent replacement.

Given the repeated occurrences of this fault, it appears this capacitor is
over stressed for its role - mechanical aspects
resulted in my replacing it with one of identical rating but if it happens
again before the TV expires I'll use a better rated part.

The meter is a microprocessor (Z8) driven autoranging device measuring from
0.01R to 99R. It will measure resistances of eg PCB tracks & wire shunts and
should prove invaluable for locating the physical location of PCB shorts.
Highly recommended.


_____________

ESR meter's own page
http://members.ozemail.com.au/~bobpar/esrmeter.htm

The creator's project page
http://members.ozemail.com.au/~bobpar/index.html

US: Another writeup & pictures here
http://www.flippers.com/esrktmtr.html

$U49.95 from here            http://www.flippers.com/esrktord-form.html

Canada
http://www.mainelectronics.com/esrkit.htm

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