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 Post subject: ESR vs Leak testing Capacitors
PostPosted: Nov Wed 08, 2017 3:20 am 
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On another forum I was getting beat up concerning using the ESR values of a capacitor to determine if it is good or bad. I contented that a leak test at the capacitors rated voltage is the best way to determine it's wear state. I have instruments that can test capacitors both ways. My Heathkit C3 can also test a cap's "Power Factor" I know this is related to Equivalent Series Resistance but I am not sure how it differs. Which test is the best one to use, ESR or the Leakage testing ? The only thing I can see with ESR testing it seems (?) to work better for in circuit testing.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Wed 08, 2017 3:50 am 
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Transmaster wrote:
The only thing I can see with ESR testing it seems (?) to work better for in circuit testing.


I concur - before we had an ESR meter, substitution was the only option - not very productive in a Sony Trinitron set with 40+ caps on the sweep board. With the ESR meter, you could walk the board, checking the caps, and quickly find 2-3 caps that were suspect. Swap the three, and voilà - another repair made simpler by an ESR meter.

Our cadre consisted of:

Creative Electronics analog ESR meter - great meter, but sensitive to temperature in the shop. On cold days, we warmed it up a bit before using.

The Electronics Australia (Dick Smith/Anatek Blue tester, later) Digital ESR meter - worked like a champ. We made a lot of money off that little tester. The only downside is that the ESR scale on the case is way too strict. Even new caps would fail if you held them to the values on the chart.

Sencore LC102 - added many more capacitor functions, but ESR and leakage were the only used. Not easy to use in circuit, as a minimum of three hands were needed.

As to old radios, I no longer test caps - just swap them out. Most are less than 10 cents new, so why bother testing the old stuff.

Cheers,

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Wed 08, 2017 5:48 am 
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ESR is an excellent test, and the standard procedure of professional technicians when working on solid state equipment filled with little electrolytic capacitors. You can check ESR quickly in circuit and determine which caps need to be replaced since they typically fail open, or nearly so.

An ESR test is not really useful for finding bad capacitors in old radios, particularly paper types which must be tested at full rated voltage for leakage current. That requires a tester like one of the Sprague TO- series which has a meter and a high voltage supply for the leakage test.

You need both types of testers if you work on both types of equipment. An ESR test will tell you nothing at all about leakage in a capacitor.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Wed 08, 2017 5:57 am 
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ESR and leakage are two different parameters of capacitors. Capacitors frequently fail one way but not the other. ESR is the series resistance in a capacitor. The most common failure that can be found with an ESR test is a dried out electrolytic capacitor. Since the electrolyte is gone, leakage is usually low. Other capacitors can fail an ESR test if contact to a lead is compromised.

On the other hand, leakage is a parallel resistance. Both electrolytic and paper capacitors can fail through high leakage, usually with low ESR.

An old-time capacitor tester like your Heathkit can do both tests. High ESR shows up by an abnormally high reading on the power factor dial. An electrolytic capacitor that has completely dried out will also have very low capacitance since one of the plates (the electrolyte) is missing. All that's left is the capacitance to the foil that formed the contact to the electrolyte.

So if you want to completely test a capacitor, you have to do both tests as well as measure the capacitance.

But as others have said, many people don't bother testing capacitors, they just replace them.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Wed 08, 2017 8:03 pm 
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On capacitor testers such as the Heath C3, the power factor knob, calibrated in power factor
is used on the highest range together with the bridge main knob. The reason for this,
is there are two bridge types available. Larger capacitors, with inherent resistance
that interferes with measurements at 60 (or 50) Hz, do not give clean nulls on the eye tube.

Both knobs are used on the higher uF range.

For that reason, the bridge model, with resistance in the known arm, is used.

Servicemen for years, interpreted power high power factor as a quality which caused
filter capacitors to heat up. This heat, caused by the real component, of the capacitor
impedance made radios hum because of reduced filtering.

Here is how the power factor relates to series resistance. Note: Often % PF is quoted.
for calculation purposes, power factor ranges from 0 to 1 . 5 % PF would be 0.05

Attachment:
Series resistance in a capacitor under test.jpg
Series resistance in a capacitor under test.jpg [ 161.13 KiB | Viewed 946 times ]

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Wed 08, 2017 8:56 pm 
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ESR and leakage testing are intended to catch two different kinds of problems. To test a capacitor fully, you need to do both. Look at it this way: if a capacitor is completely open, there will be no leakage so a leakage test will tell you it is perfect. On the other hand, an ESR test will show the impedance to be impossibly high. Should a capacitor be shorted or excessively leaky, an ESR test may well read perfect but a leakage test will surely flag it.

One thing that needs to be understood is, the chemistry in many electrolytics changed around 1970. Prior to that, all electrolytes were water based. After 1970, glycol based electrolytes came into use for many kind of electrolytic caps. In any electrolytic capacitor, the electrolyte is gradually lost. Some of it is broken down by electrolysis and the oxygen is used to reform and maintain the aluminum oxide dielectric layer. Inevitably, some electrolyte is also lost due to evaporation through seals and end plugs.

Now in a water based capacitor, when the electrolyte is no longer capable of replenishing the dielectric layer, it deforms and leakage current increases until the cap shorts out. In a glycol based capacitor, the electrolyte loses its ionic concentration and its ability to carry current is lost. It goes high in ESR and maybe becomes open. This is why you won't find any antique ESR testers, and they're not mentioned in old radio repair textbooks. Nobody needed them until more recently.

ESR, power factor, tan-delta, and dissipation are all related, and it is possible to convert from one to the others if enough data is available. Strictly speaking, proper determination of ESR requires the dielectric constants involved and some knowledge of the physical construction of the cap. For practical purposes, ESR is measured with an impedance meter. If we calculate the ideal reactance of the capacitor at the meter's test frequency and subtract that amount from the reading; what remains is approximately the ESR.

Power factor is based on the understanding that a perfect capacitor shifts the phase of the current passing through it relative to the voltage by 90 degrees. If the capacitor is less than perfect, i.e. it has resistance, that phase angle will be less than 90 degrees. AC bridge circuits require that both voltage and phase be in balance to get a null, making it easy to measure the angle between them which is given its own special name, loss angle. The tangent of the loss angle, taken as a percentage, is the power factor. It is also known as the tan-delta of the capacitor. (The term power factor implies the loss at AC power frequencies like 60 Hz or 120 Hz, while tan-delta can be measured at any frequency). Tan delta is equal to dissipation factor or DF.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Thu 09, 2017 7:02 am 
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Chris108 wrote:
ESR and leakage testing are intended to catch two different kinds of problems. To test a capacitor fully, you need to do both...

+1

Although to be honest, I've done one or the other - not both - on occasion. Depends on the circumstances.

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Last edited by WPE9IJF on Nov Sun 12, 2017 7:17 pm, edited 1 time in total.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Thu 09, 2017 8:03 am 
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A good fast way to test paper or plastic capacitors for 'goodness' is to connect, a 47k resistor,
a 2 meg linear pot, a 90 volt battery and the capacitor in series.

Then connect a NE2 across the capacitor. Turn the pot until the neon bulb starts to flash.

No flash, no good.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Sat 11, 2017 2:53 pm 
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radiotechnician wrote:
A good fast way to test paper or plastic capacitors for 'goodness' is to connect, a 47k resistor,
a 2 meg linear pot, a 90 volt battery and the capacitor in series.

Then connect a NE2 across the capacitor. Turn the pot until the neon bulb starts to flash.

No flash, no good.

Wow, sounds neat, but then I wouldn't have any reason to use my Heathkit capacitor checker! :roll:

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Sat 11, 2017 2:59 pm 
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Cost of new capacitor?
Cost of your time to check the old one?

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Sat 11, 2017 3:48 pm 
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pixellany wrote:
Cost of new capacitor?
Cost of your time to check the old one?


+1, with an exception - solid state stuff of recent manufacture. Replacing 40+ caps is unnecessary, when only one or two is bad....

As to checking both leakage and ESR......

Ease of checking leakage in circuit? Can't do it - it's what brought about in-circuit ESR testers - bad ESR, bad cap. No leakage testing required, and the ESR can be checked in circuit, with ease and speed. Every tool in our toolbox was created to fill a need.....

Me? I don't NEED to test leakage - as Mark points out, just replace the paper caps and electros in vintage stuff and move on. A commercial leakage tester just becomes an expensive bench sitter...

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Sun 12, 2017 7:23 pm 
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Findm-Keepm wrote:
pixellany wrote:
Cost of new capacitor?
Cost of your time to check the old one?
...Me? I don't NEED to test leakage - as Mark points out, just replace the paper caps and electros in vintage stuff and move on. A commercial leakage tester just becomes an expensive bench sitter...

You guys are right but you're getting all logical here.... :wink: I have FUN testing them, just to see how leaky (or not) they are...

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Sun 12, 2017 8:27 pm 
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Findm-Keepm wrote:
pixellany wrote:
Cost of new capacitor?
Cost of your time to check the old one?
+1, with an exception - solid state stuff of recent manufacture.
The name of this site is Antique Radios.com

Why would we be discussing "solid state stuff of recent manufacture" ?

- Leigh

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Sun 12, 2017 9:34 pm 
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Leigh wrote:
Findm-Keepm wrote:
pixellany wrote:
Cost of new capacitor?
Cost of your time to check the old one?
+1, with an exception - solid state stuff of recent manufacture.
The name of this site is Antique Radios.com

Why would we be discussing "solid state stuff of recent manufacture" ?

- Leigh

To some that frequent this site solid state is antique.

Dave


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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Mon 13, 2017 3:52 am 
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Leigh wrote:
Findm-Keepm wrote:
pixellany wrote:
Cost of new capacitor?
Cost of your time to check the old one?
+1, with an exception - solid state stuff of recent manufacture.
The name of this site is Antique Radios.com

Why would we be discussing "solid state stuff of recent manufacture" ?

- Leigh

That's easy---because is relevant to the topic being discussed. If that doesn't do it for you, then note that I did not define "recent"..... I gravitate towards 1930-ish brick schoolhouse radios. Under duress, I also fix 1970s stuff. I still call that vintage, and I replace all the caps. If I'm fixing a 2008 toaster, I might not touch the caps at all.....;)

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Thu 16, 2017 1:23 am 
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I'm in favor of owning and using the maximum amount of test equipment possible! That said, one thing I don't own and have never needed is an ESR tester. ESR is typically a 100 kHz test and the only people who care about 100 kHz performance are switching supply designers. There's nothing about an ESR tester that's any better at doing in-circuit measurements than a 120 Hz measurement (or 1 kHz for small caps). I happily go from cap to cap using an old GR 1657 Digibridge and some long pointy leads, knowing that I'll spot bad caps regardless of whether the problem is value or losses. The only requirement is that the test voltage be low enough not to turn on semiconductors, which is almost always the case. I've run across quite a few caps whose only problem is low value, showing perfectly normal and acceptable losses. ESR tester can't spot those. IMO, the big strength of ESR testers is they're usually not too expensive, hand-held and floating. Similar complaint for "cap-meters". You get the value, but no clue if the losses are out of sight. The only thing you can't do with any tool is in-circuit DC leakage, and I don't have an answer for that.

You can convert any type of value and loss numbers to any other- my free utility here: http://www.conradhoffman.com/chsw.htm first item on the list. Go to the electronics page for more stuff on caps and losses.


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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Fri 17, 2017 8:06 am 
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Conrad Hoffman wrote:
I'm in favor of owning and using the maximum amount of test equipment possible.......

I'm the opposite....I use only test equipment where I am smart enough to interpret the results. That leaves me with a pretty barren workspace. ( which in turn makes room for more unfinished projects.....;) )
Most capacitor testing is with the "trash can test"-- typically attributed to Curt Reed. Beyond that, it's an impedance bridge and a general-purpose HV supply.

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Fri 17, 2017 8:38 am 
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easyrider8 wrote:
Leigh wrote:
Findm-Keepm wrote:
+1, with an exception - solid state stuff of recent manufacture.
The name of this site is Antique Radios.com

Why would we be discussing "solid state stuff of recent manufacture" ?

- Leigh

To some that frequent this site solid state is antique.

Dave

Indeed. Transistor equipment has been around since the mid-fifties, or about 60 years ago. If that time span don't qualify as gravitating toward antiquity, I dunno what does.

And of course the best test for the few caps that were in the early solid state receivers, would be whether they made a clunking sound as they hit the "circular file" receptacle... :wink:

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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Fri 17, 2017 7:08 pm 
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It's hard to go wrong with the "clunk" test. :mrgreen:


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 Post subject: Re: ESR vs Leak testing Capacitors
PostPosted: Nov Fri 17, 2017 7:23 pm 
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fifties wrote:
Transistor equipment has been around since the mid-fifties, or about 60 years ago. If that time span don't qualify as gravitating toward antiquity, I dunno what does.
True.

And I was repairing many of those radios when they were new, so I don't consider them "antique".
If I did, I would have to call myself "antique", and I don't choose to do that.

fifties wrote:
And of course the best test for the few caps that were in the early solid state receivers, would be whether they made a clunking sound as they hit the "circular file" receptacle... :wink:
Definitely agree with that.

- Leigh

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