DSE ESR meter.

[ian field]

Since getting hold of one of these kits and putting it to use, I've been
getting the impression that modern electrolytics are manufactured with much
lower ESR than was anticipated when the meter was designed and now I suspect
that electrolytics with ESR values approaching the values in the table
printed on the front panel might cause problems in modern fast switching
PSUs.

Is there a revised table I can print out and stick over the old one?

TIA.

 

[Mark Harriss]

On Thu, 07 Feb 2008 03:06:15 +1000, ian field <dai.ode@ntlworld.com> wrote:

Since getting hold of one of these kits and putting it to use, I've been
getting the impression that modern electrolytics are manufactured with
much lower ESR than was anticipated when the meter was designed and now
I suspect > that electrolytics with ESR values approaching the values in
the table printed on the front panel might cause problems in modern fast
switching PSUs.

Is there a revised table I can print out and stick over the old one?

TIA.

Those values were for a "worst case" value for those capacitances.
I was under the impression that they were derived from cheap and nasty
electros similar to "Joe Master" brand that DSE are so fond of stocking.

 

[Bob Parker]

On 7/02/2008 04:06 ian field wrote:

Since getting hold of one of these kits and putting it to use, I've been
getting the impression that modern electrolytics are manufactured with much
lower ESR than was anticipated when the meter was designed and now I suspect
that electrolytics with ESR values approaching the values in the table
printed on the front panel might cause problems in modern fast switching
PSUs.

Is there a revised table I can print out and stick over the old one?

TIA.

The charts on the front of the Mk1 and Mk2 ESR meters were only ever
meant as a rough guide to what to expect until the user gets familiar
with using the meters in real-world repairs.
The Mk1 meter's chart was derived from an old capacitor catalogue,
and the Mk2 meter's chart was the end result of me measuring a big pile
of unused electrolytic caps and averaging out the values as best I
could. The figures were all over the place.
The Mk2 meter chart in text form is at
http://members.ozemail.com.au/~bobpar/2003esrchart.txt
Except in very rare cases, the ESR of an electrolytic cap which is
causing problems will be found to be >10 times what the charts say, more
often >30 times or above 99 ohms (the meter's maximum reading).
There's only one repair situation I know of where ESR is critical -
in one capacitor in one type of switching power supply which is
sometimes found in older Sanyo, Teac and a few other TVs. An
electrolytic cap which is usually about 47uF/25V connects from the base
of the switching transistor to the collector of a control transistor,
allowing the control transistor to progressively short out the switching
transistor's base drive and control the output voltage.
When that cap develops an ESR of maybe 10 ohms or more, the power
supply loses regulation and the main B+ rail goes higher and higher,
taking out a lot of circuitry and sending the EHT very high. It's a
really stupid fail-UNsafe design.
I hope this might have clarified things a little bit.

BTW ... has anyone here bought one of the Altronics ESR meter kits
yet? If so, I'd like some constructor comments because I've never seen
one.



Cheers
Bob