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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Tue Jun 28, 2011 12:13 am Post subject: ESR, what is it? Cause and effect and how to test it? |
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I figure since the forum is a bit slow now, it might be a good idea to review a topic that all could benifit by.
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Chip
A Barco is only a AmPro with training wheels
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Tue Jun 28, 2011 6:29 am Post subject: |
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It is abit slow these days isnt it.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Jun 28, 2011 7:06 am Post subject: ESR: My try on a definition |
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Good Morning,
ESR is a term used in conjunction with capacitors, especially electrolytic capacitors. In this context it means "Equivalent Series Resistance" and is an indicator for the capacitor's ability to supress ripple currents.
In general a capacitor will represent a high impedance resistor as long as the current supplied to it will change slowly. The faster the change is the lower the impedance will be until it eventually will reach its minimum where the capacitor will almost represent a short circuit. This behaviour is directly dependant on the device's capacitance (measured in farads).
Thus electrolytic capacitors are mostly used for power supply rails in order to "short circuit" ripple currents to GND. The lower the ESR is the better this "short circuit" will be.
Unfortunately these devices experience aging which will result in loss of capacitance and increase in ESR. The main factor for aging is the liquid electroyte which will evaporate over time. Poorly designed circuits, low security margins (due to cost retraints), high temperature environments and/or low quality capacitors can speed up this process.
Sometimes but not always such electrolytic capacitors will show case bulging, rupture, or even an explosion. Of course in this case they won't be able to perform properly and additional circuit failure is immanent.
Capacitance and ESR can be measured with specific instruments designed for this purpose.
I recommend the corresponding Wikipedia articles (look for "Capacitor" and "Capacitance meter").
Regards,
barclay66
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Tue Jun 28, 2011 7:48 am Post subject: |
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Gday Barclay 
So when replacing capacitors within these projectors, would it be best to go with the low ESR caps for every cap you replace??
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Jun 28, 2011 9:05 am Post subject: |
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Whenever filtering is the capacitor's main purpose (e.g. Power supplies, supply lines on modules etc.) I would choose low ESR types and higher temperature tolerance (105°C instead of 85°C). Capacitance value should generally be the same (some tend to increase capacitance by 10-30% when replacing caps, I haven't seen any benefit though). Maximum voltage can of course be chosen higher (increase in reliability). Sometimes space is the limiting factor then.
In case the capacitor is used for other purposes (e.g. signal coupling) I would look for a direct replacment with similar specs...
Regards,
barclay66
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kabuby77
Joined: 28 Mar 2011
Posts: 147
Location: Italy
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| Posted: Tue Jun 28, 2011 9:16 am Post subject: |
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Be careful, the stability of some circuits is related to the value of ESR in the capacitor. Do not make changes to circuits where you do not understand the function.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Jun 28, 2011 10:54 am Post subject: |
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Of course. A one-to-one replacement should never make things worse... 
Regards,
barclay66
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Tue Jun 28, 2011 11:05 am Post subject: |
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Great post Barclay. I was going to let this just sit here for a while and see what pops up and then list questions one at a time but you took the wind out of my sails. So are you saying,
*low ESR = low resistance to ground (almost shorted)?
*High ESR = high resitance to ground (almost open)?
* When the electrolyte has leaked/evaporated from a of a capacitor, it's it's resistance to ground is higher (high ESR)?
As the thread progresses, I'll be injecting questions until answers pop up that everyone understands.
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Chip
A Barco is only a AmPro with training wheels
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Tue Jun 28, 2011 11:29 am Post subject: |
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| stefuel wrote: | | Great post Barclay. |
Thank you!
| stefuel wrote: | | As the thread progresses, I'll be injecting questions until answers pop up that everyone understands. |
One could think you already know the answers and that you only want to se the puppets play... 
| stefuel wrote: | | *low ESR = low resistance to ground (almost shorted)? |
Yes, but that only applies to higher frequencies (exactly what ripple currents are on a DC supply line).
You can compare that to a damper in a car and its effect on a bumpy road.
| stefuel wrote: | | *High ESR = high resistance to ground (almost open)? |
Yes, that's when the damper comes loose.
| stefuel wrote: | | *When the electrolyte has leaked/evaporated from a of a capacitor, it's it's resistance to ground is higher (high ESR)? |
Yes. In addition the capacitance will be reduced (its ability to hold a charge).
Regards,
barclay66
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Jun 28, 2011 2:23 pm Post subject: |
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High ESR caps are a 'make work' project for technicians that need something to do.
I bought my ESR meter on eBay for about $200. Works fine, I use it daily, but have also been thrown off, as it runs on 100Khz or so to measure the ESR. I have had more than 1 cap now that opened up (220 uF down to about 1uF), but the ESR still read as being good.
Also, surrounding circuits can provide other means of low ESR, even if the cap you're measuring is bad.
My related question to this topic and post is:
When caps leak and fail with high ESR, is it just cheap construction, high ambient temperatures, or a cap that's too close in rated voltage to the circuit that causes it to fail? Or is it a combination of all of that?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Jun 28, 2011 2:31 pm Post subject: |
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| Curt Palme wrote: |
When caps leak and fail with high ESR, is it just cheap construction, high ambient temperatures, or a cap that's too close in rated voltage to the circuit that causes it to fail? Or is it a combination of all of that? |
Lol, your flat panel experience is showing through on this question.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Jun 28, 2011 2:38 pm Post subject: |
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| Nashou66 wrote: | Mac when you get time you need to finish what you started on the cap thread buddy!!!
Athanasios |
LOL, I was telling Chip, with summer here I'm outside more and not on the PC as much. Maybe in the fall.... 
I'm refraining from responding in this thread (for now). Curious to see how it all plays out... 
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Tue Jun 28, 2011 9:09 pm Post subject: |
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| macgyver655 wrote: | | Nashou66 wrote: | Mac when you get time you need to finish what you started on the cap thread buddy!!!
Athanasios |
LOL, I was telling Chip, with summer here I'm outside more and not on the PC as much. Maybe in the fall....
I'm refraining from responding in this thread (for now). Curious to see how it all plays out... |
I was hoping this thread would smoke you out
I read all ten pages of your cap thread but then it just stopped. It was like driving by someons house and seeing half the lawn mowed
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Chip
A Barco is only a AmPro with training wheels
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Tue Jun 28, 2011 9:20 pm Post subject: |
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| stefuel wrote: | | macgyver655 wrote: | | Nashou66 wrote: | Mac when you get time you need to finish what you started on the cap thread buddy!!!
Athanasios |
LOL, I was telling Chip, with summer here I'm outside more and not on the PC as much. Maybe in the fall....
I'm refraining from responding in this thread (for now). Curious to see how it all plays out... |
I was hoping this thread would smoke you out
I read all ten pages of your cap thread but then it just stopped. It was like driving by someons house and seeing half the lawn mowed |
For a year!!!
Nashou
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stefuel
Joined: 07 Mar 2006
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Location: Green Harbor MA USA
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| Posted: Tue Jun 28, 2011 9:23 pm Post subject: |
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I have a ESR70 on the way. It should be here tomorrow or the next day, which is kinda what got me thinking about starting a ESR thread 
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Chip
A Barco is only a AmPro with training wheels
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CasetheCorvetteman
Joined: 09 Nov 2008
Posts: 6326
Location: Australia
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| Posted: Wed Jun 29, 2011 6:59 am Post subject: |
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Where is this cap thread?
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Wed Jun 29, 2011 7:46 am Post subject: |
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| Curt Palme wrote: | | When caps leak and fail with high ESR, is it just cheap construction, high ambient temperatures, or a cap that's too close in rated voltage to the circuit that causes it to fail? Or is it a combination of all of that? |
Hi,
I've been working on many different display devices such as CRT TVs, CRT Projectors, Plasma TVs and LCD TVs over the last 30 years. When I look back at these experiences I would conclude that it mostly IS a combination of different factors:
- Power supply design has moved from linear to switched power supplies which -> Much higher stress on capacitors
- Enhanced product attractiveness through lightweight and noiseless design -> Ventilation and/or active cooling are scaled down
- Cost efficiency is the order of the day -> Design and testing are cut short
- Cost efficiency is the order of the day -> Production will use the cheapest available components that meet the specs (on paper)
- Cost efficiency is the order of the day -> Controls at goods receiveing are reduced
- Partial or complete outsourcing of production -> Loss of control at component level
- Quality problems at capacitor fabrication -> Batches with reduced lifespan (yes, this happens)
- The lifespan of an inexpensive consumer product -> It has to be limited in order to support the economy
I don't want to start a rant on who's the culprit. The only thing I can say is that I still own some Grundig (German brand) TV sets from 1979 that still work perfectly without having to have them recapped. If this is due to their linear power supply (they do have a huge mains transformer), the meticulous and expensive design (each module encapsulated in its own aluminium case) or just because the world must have been better in former times (as some people think) I really can't say.
This statement is NOT intended to create the impression that German engineering may be better than others. In fact the mentioned line of TV sets created a lot of problems for its developers. The design was very expensive although competition inhibited an adecuate pricing of the sets. The sets were very heavy and the sealed modules weren't field repairable (exchange program only). And finally the sets lasted too long which negatively affected sales of the subsequent line. Many technicians think that this line was one of the first steps to Grundig's demise...
Regards,
barclay66
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