capacitor testing

H

h.godavari

Guest
Is there an easy way of testing the capacitors on a motherboard (without
elaborate equipment)? These are electrolytic caps on a computer mother
board(MS 6380E). thanks for your help.
regards
hg
 
"h.godavari" <h.STOPgodavari@shaw.STOPca> wrote in message
news:RF0Gl.24622$Qh6.18111@newsfe14.iad...
Is there an easy way of testing the capacitors on a motherboard (without
elaborate equipment)? These are electrolytic caps on a computer mother
board(MS 6380E). thanks for your help.
regards
hg
Click to expand...

Aside from the rated capacitance value, the ESR (Equivalent Series
Resistance) is probably the single most important characteristic of a
capacitor used in a switch mode power supply/regulator.
I heartily recommend that you invest in an ESR meter. There are a number of
different models and types available. Bob Parker designed and sold a
well-known and widely used kit a number of years ago, one of which I have
been using for several years with great results.
Here are a few links to get you started:
http://members.ozemail.com.au/~bobpar/esrmeter.htm
http://mainelectronics.com/esrkit.htm
http://www.flippers.com/esrktmtr.html
http://www.howardelectronics.com/ieinc/cwinfo.html

Different people aspire to different models, depending on personal
preference, but in the end, they all do the job quite well if used properly.
While there is no absolute value for the ESR of a particular type and value
of capacitor, some manufacturers do publish the maximum ESR values of
certain lines of their capacitors. You'll have to surf the mfr's sites to
find those.

Good luck!
--
"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

Dave M
masondg44 at comcast dot net
 
Is there an easy way of testing the capacitors on a motherboard (without
elaborate equipment)? These are electrolytic caps on a computer mother
board(MS 6380E). thanks for your help.
Click to expand...
Yes. The commonest failure mode of such capacitors is an increase in
the equivalent series resistance (ESR). It's possible to test this
in-circuit, with relatively simple equipment.

One possibility is shown at

http://ludens.cl/Electron/esr/esr.html

which is something you can breadboard together pretty easily... I've
built one and just have to stick it in the final case (maybe next week).

An even simpler approach is to use a function generator (you need a
sine or square wave at a few tens of kHz and at somewhere around a
tenth of a volt), a couple of resistors, and an oscilloscope.

See the page at

http://octopus.freeyellow.com/esr.html

for a simple schematic, and links to a bunch of other projects.

You can buy commercial capacitor ESR testers (complete or as kits).
I've heard tgood things about the AnaTek Blue meter (around $80 - see
http://www.anatekcorp.com/blueesr.htm).

The neat thing about all of these testers, is that you can use them
in-circuit - there's no need to unsolder the capacitors prior to
testing. Just make sure you've powered down the board and allowed all
of the caps to self-discharge safely.

Oh... if any of the caps are bulging at the top, or have started to
split at the pressure-relief seam and/or to leak fluid... you can
assume that they're bad.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
 
Whoops hit the wrong button. Here is what I wanted to post:

http://www.eds-inc.com/cap.html
 
On Fri, 17 Apr 2009 09:49:58 -0500, "h.godavari"
<h.STOPgodavari@shaw.STOPca> put finger to keyboard and composed:

Is there an easy way of testing the capacitors on a motherboard (without
elaborate equipment)? These are electrolytic caps on a computer mother
board(MS 6380E). thanks for your help.
regards
hg
Click to expand...
The difficulty with testing capacitors on a motherboard is that there
are several connected in parallel. This means that an ESR test may not
find a bad cap because a good one may mask it. Furthermore, even if
all 5 caps, say, in a parallel Vcore set are bad, you will still need
to multiply the meter's ESR reading by 5 to get the individual ESR
value.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
Ken Layton wrote:
Whoops hit the wrong button. Here is what I wanted to post:

http://www.eds-inc.com/cap.html

It looks good Ken but a bit rich for my pocket :-(
Click to expand...

regards
hg
 
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