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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Nov 20, 2009 9:39 pm Post subject: |
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| Nashou66 wrote: | | dturco wrote: | Where was this 5 minute post? All I see is a request for 5 people for Mac to continue. I have found this very interesting although it's not going to help me, I'm sure it will help many others.
So Mac, please continue.  |
Oooops!! my bad, your right. Yeah this will be a good lesson.
I think I'll bring an apple for the teacher this class lesson.
I have another topic I want to get Rons opinion on as this guy gets blocked for his radical views on SRF.
Look up Ivor Cat this is what i am curious about http://www.ivorcatt.com/2603.htm
Athanasios |
Hmmmm. Sounds like you and Jask want to get into operating characteristics of capacitors. Operating characteristics have petty much nothing to do with cap life, which was the main reason for my topic thread. Also it would only apply to design and engineering of a circuit. Very few people on here would be interested in that sort of discussion so I probably wont get involved in it.
As far as SRF, I have read Ivor Cat's stuff before along with many other documents.
Did you have a specific question?
I agreed to discuss ESR because its a term used daily, its something thats real and can apply to regular electronics repair. So I will write some stuff on that. I've been involved in a couple other things lately so as soon as I get a chance, I'll start on ESR.
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Fri Nov 20, 2009 10:04 pm Post subject: |
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Dude, If you need to take a break, do so. But whatever you do, don't abandon this thread - do keep it coming!
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jask
Joined: 17 Mar 2006
Posts: 10187
Location: kamloops BC
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| Posted: Sat Nov 21, 2009 4:44 am Post subject: |
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| Quote: | In a switching power supply, the voltage coming out of the O/P rectifier and into the O/P inductor is a positive-polarity square wave. The O/P inductor and O/P capacitor(s) filter that into a DC voltage. The current through the inductor is a DC level (which goes to the load) with triangle-shaped AC current riding on the DC level. The AC current is due to the charging of the inductor (during the switch "On" time) and discharging of the inductor (during the switch "Off" time). If things are designed properly and operating normally, the inductor never "fully" charges (saturation), nor discharges fully. Almost all of the AC current, several amps rms, goes through the O/P capacitors rather than to the load (if it did, the ripple voltage would be fairly high). While a capacitor's DC resistance is very high, its impedance to AC depends on the frequency of the AC. In the 100KHz range, that impedance is milliohms (thousandths of an ohm). By way of contrast, the effective resistance on the load in the computer is much higher (e.g., if the O/P voltage is 2V and the load current is 20A, the DC "resistance" is 100 milliohms). So it is entirely normal for the capacitors to be conducting several amps of ripple current, as this is due to the capacitors' smoothing action.
What is impedance? In a capacitor, it has 3 basic components in series with each other: an ideal capacitor; the ESL, equivalent series inductance, of the leads; the equivalent series resistance of the leads, the foils, and the electrolyte. Impedance is the vector sum of the capacitive reactance [1/(6.28xFxC)] X(C), the inductive reactance (6.28xFxL) X(L), and the ESR. At relatively low frequencies, X(C) is basically the impedance. As frequency increases, the impedance falls until the ESR is greater than the X(C), and the ESR is basically the impedance. As frequency continues to rise, the X(L) becomes greater than the ESR, and the impedance is basically the X(L). P/Ss and VRMs operate in the frequency range where the impedance and ESR are approximately the same.
If the capacitor is conducting ripple current, it is dissipating power (I^2)(ESR), which is heat. The higher the ripple current, the more the heat. If you exceed the ripple current rating, the cap will overheat, unless the ripple current is so high that hydrogen gas is being generated. So the failure mechanisms with excessive ripple current are electrolyte evaporation and evaporation- or gas-related venting.
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I am posting this to continue the discussion in terms of how high rms kills low spec caps at high frequency.
This was originally posted in the badcaps forum. For most of us the issue is not old caps , it is old caps that are being exposed to high stress then fail and take out other components. Prophylactic replacement of caps is not about useful service life of specific caps.When you have a projector that has a service bulletin that addresses known failures, these are addressing inherent design weaknesses-...by itself or as part of a system- either the cap (or other component..) was underrated or the higher stress of H.D. bandwidth is causing the projector to "push the envelope" and fail.We are the "sunset"users of this engineering and are asking more of the gear today than was normally expected of it at the time it was engineered(years before it was built... with components that are sometimes obsolete today!!)long before 40Mbps (Bluray) would have been considered a "normal" source.
I do not doubt the studies cited, but in real service lots of audiofools have killed classic gear by simply plugging it in and powering it up to full voltage when it has been sitting unused for years.
Bad caps are job security for electronics techs.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Sat Nov 21, 2009 1:54 pm Post subject: |
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Nice post Jask you make lots of Valid points there. All though some of our Pj's have been upgraded by the Manufacture to handle the higher bandwidth sources. like the Late model Sony's,Barcos,And the latest VDC projectors. But for anything older i agree that for lower bandwidth uses like 1080i@60 they would fare well for long periods of use but start going higher those components may fail and maybe Updated components(not only caps) would fare better.
Athanasios
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Nov 21, 2009 8:52 pm Post subject: |
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| jask wrote: | | Quote: | In a switching power supply, the voltage coming out of the O/P rectifier and into the O/P inductor is a positive-polarity square wave. The O/P inductor and O/P capacitor(s) filter that into a DC voltage. The current through the inductor is a DC level (which goes to the load) with triangle-shaped AC current riding on the DC level. The AC current is due to the charging of the inductor (during the switch "On" time) and discharging of the inductor (during the switch "Off" time). If things are designed properly and operating normally, the inductor never "fully" charges (saturation), nor discharges fully. Almost all of the AC current, several amps rms, goes through the O/P capacitors rather than to the load (if it did, the ripple voltage would be fairly high). While a capacitor's DC resistance is very high, its impedance to AC depends on the frequency of the AC. In the 100KHz range, that impedance is milliohms (thousandths of an ohm). By way of contrast, the effective resistance on the load in the computer is much higher (e.g., if the O/P voltage is 2V and the load current is 20A, the DC "resistance" is 100 milliohms). So it is entirely normal for the capacitors to be conducting several amps of ripple current, as this is due to the capacitors' smoothing action.
What is impedance? In a capacitor, it has 3 basic components in series with each other: an ideal capacitor; the ESL, equivalent series inductance, of the leads; the equivalent series resistance of the leads, the foils, and the electrolyte. Impedance is the vector sum of the capacitive reactance [1/(6.28xFxC)] X(C), the inductive reactance (6.28xFxL) X(L), and the ESR. At relatively low frequencies, X(C) is basically the impedance. As frequency increases, the impedance falls until the ESR is greater than the X(C), and the ESR is basically the impedance. As frequency continues to rise, the X(L) becomes greater than the ESR, and the impedance is basically the X(L). P/Ss and VRMs operate in the frequency range where the impedance and ESR are approximately the same.
If the capacitor is conducting ripple current, it is dissipating power (I^2)(ESR), which is heat. The higher the ripple current, the more the heat. If you exceed the ripple current rating, the cap will overheat, unless the ripple current is so high that hydrogen gas is being generated. So the failure mechanisms with excessive ripple current are electrolyte evaporation and evaporation- or gas-related venting.
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I am posting this to continue the discussion in terms of how high rms kills low spec caps at high frequency.
Most of this again has to do with design and cannot be used as a global issue. It all depends on the circuit the cap is being used in. There are probably atleast a dozen various capacitor operating characteristics however they dont all apply in every circumstance. In one location high rms or ESL will have no affect. In another location SRF and even ESR will have almost no affect. Even in a circuit with high rms, a slight alteration in the design can resolve the rms issue without involving a specialty cap.
This is why I didn't really want to get into operating characteristics. Any discussion would have to pertain to a specific circuit with specific parameters in the discussion. There is not a global answer.
However if you guys want to begin discussing operating characteristics in this thread then go right ahead. I may jump in on occasion but I wont begin a discussion. As I did here.
This was originally posted in the badcaps forum. For most of us the issue is not old caps , it is old caps that are being exposed to high stress then fail and take out other components.
Prophylactic replacement of caps is not about useful service life of specific caps.
This is what was being clarified in this thread. Glad you've been paying attention...
When you have a projector that has a service bulletin that addresses known failures, these are addressing inherent design weaknesses-...by itself or as part of a system- either the cap (or other component..) was underrated or the higher stress of H.D. bandwidth is causing the projector to "push the envelope" and fail.We are the "sunset"users of this engineering and are asking more of the gear today than was normally expected of it at the time it was engineered(years before it was built... with components that are sometimes obsolete today!!)long before 40Mbps (Bluray) would have been considered a "normal" source.
I agree with the first part but question the second part about bandwidth. The part in question means, leaving out earily designed projectors with very limited bandwidth, if we were to look at higher bandwidth projectors its difficult to state they are not designed to handle this bandwidth based on the developement and use of BluRay. Line tripler, quadruplers and scalers have been around before bluray was just a dream and also before a pc was even capable on playback of full motion video. So in actually they were designed for higher bandwidth use.
Also it must be known that there are very few areas of a projector that are even affected by higher bandwidth.
However I do agree there are areas that do fall under more strain with higher bandwith use.
I do not doubt the studies cited, but in real service lots of audiofools have killed classic gear by simply plugging it in and powering it up to full voltage when it has been sitting unused for years.
This analogy I have a problem with. When your talking classic gear your looking a negatives to begin with. You have capacitors with very limited build quality. Some caps had a paper cardboard exterior, had only low temp operating capability, had very short life based on then technology. Plus very poorly designed circuits to handle higher currents and higher temps from tubes and other components. These classic audio devices had a very limited life even when in regular use. Chances are they were ready to fail or even already partially failed when they went into storage. This should be a no brainer that these types of devices should be gone over and rebuilt before being attempted to use.
Bad caps are job security for electronics techs.
I guess this is correct. A tech does want to make sure he replaces a bad cap, lol. I guess the question is the relevance of recapping an entire board.
So let me put it this way. There is nothing wrong with rebuilding a board with new parts. Actually I believe its a good thing as long as your making sure your getting good replacements. Its just difficult to make certain claims of a general outcome.
Think of it like this. You have a car thats 20 years old and has 150,000 miles on it, but still has good oil pressure, doesn't use oil and starts and runs fine. Now someone suggests rebuilding the motor. Now rebuilding the motor may be a good thing so as to insure a longer life from that point on, but also doesn't mean you would not have gotten a long life even if you didn't rebuild it. Also it doesn't mean it will run better if you rebuild it.
Now if it had a bad part, thats a different story but also doen't mean if you didn't just replace that bad part you still wouldn't get a long life out of it.
Did you follow that ok. I think I explained it fairly well.
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Sat Nov 21, 2009 10:37 pm Post subject: |
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"prophylactic caps"
Are those the really small ones made by Trojan 
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tse
Joined: 03 May 2006
Posts: 1014
Location: Sweatbucket, Fl.
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| Posted: Sun Nov 22, 2009 1:25 am Post subject: |
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The top line projectors were designed for 1280x1024 way back when. That was exotic stuff in the day. 64kHz scan rate. It is not much of a leap to 1080p with its 68kHz scan rate. CRT projectors were well ahead of their time.
Scott
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sat Dec 19, 2009 5:30 pm Post subject: |
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I forgot to post a few things on this subject when the thread was hot. I wanted to see if you would post a few ways to check a cap even if it checks OK on a good cap tester.
I took pictures of a cap that checked OK on my cap tester. And it's present condition barely shows it's weak in the circuit. But after opening it up. There's three things that reveal that it's bad, even after the cap tester shows it's OK:
I'm sure you already know this, but (1) a larger sized cap you can bounce around in your hand. (2) smell. (3) squeeze test.....
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Dec 19, 2009 6:31 pm Post subject: |
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Which test did it pass Mike? Value test or ESR? Or both?
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sat Dec 19, 2009 6:32 pm Post subject: |
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| macgyver655 wrote: | | Which test did it pass Mike? Value test or ESR? Or both? |
Value - it read 470mf.....
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Dec 19, 2009 7:23 pm Post subject: |
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So you didn't ESR it? Do you have an ESR meter?
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sat Dec 19, 2009 8:31 pm Post subject: |
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| macgyver655 wrote: | | So you didn't ESR it? Do you have an ESR meter? |
No, neither of my cap testers have ESR read out.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Dec 19, 2009 10:14 pm Post subject: |
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| mp20748 wrote: | | macgyver655 wrote: | | So you didn't ESR it? Do you have an ESR meter? |
No, neither of my cap testers have ESR read out.
. |
Well I can tell right off the bat you are an old school repair tech, just like myself, Curt and a few others on here.
I know I was reluctant to believe in ESR testing and the funky meters but let me tell you that this is the only way to now test cap condition. The ESR tester will allow you to test in circuit (power off) and will indicate a bad cap even if it checks good value wise. The value tester is still good to test a new cap to make sure it has the correct value for the one your replacing but the ESR tester is the only way to test them anymore.
I know this was suppose to be the next part of my thread here and I've been lazy about writing the post, mostly because it will be fairly lengthy so it is understandable. Cap ESR can be difficult to understand but I think I can explain it well.
I guess now I have to continue with the ESR part.
THATS ALOT MIKE...........
As soon as I have some time I'll write it up.
And get yourself an ESR tester. You wont regret it. Just ask Curt. He loves his Cap Wizard.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Dec 19, 2009 10:16 pm Post subject: |
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Oh, and dont bother with an expensive one. I think Curt paid 200 bucks for his.
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sat Dec 19, 2009 10:24 pm Post subject: |
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Well, that explains why that cap got pass me and made me open it up for inspection..
I'd like to test one of these same caps from the same circuit with an ESR tester.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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jask
Joined: 17 Mar 2006
Posts: 10187
Location: kamloops BC
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| Posted: Sun Dec 20, 2009 5:45 am Post subject: |
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I have one of the original Bob Parker units that I built from a kit, it has been updated and is still one of the cheapest if you buy the kit : http://www.anatekcorp.com/blueesr.htm
On the down side it does not have a beep/audible function, but a few guys on the web have added one...
I like the cap wizard but when mine eventually dies ( or I find a good excuse..) I plan on buying an Atlas:
Bob Parker also made a ring tester for flyback/inductor testing (anatek also sells it) and the schematic is on the web, I do not "really" need one but am planning on building one just to try it out....and because I have a tiny project box with a strip LED already mounted on it in my junk box
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sun Dec 20, 2009 6:29 am Post subject: |
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| jask wrote: | I have one of the original Bob Parker units that I built from a kit, it has been updated and is still one of the cheapest if you buy the kit : http://www.anatekcorp.com/blueesr.htm
On the down side it does not have a beep/audible function, but a few guys on the web have added one...
I like the cap wizard but when mine eventually dies ( or I find a good excuse..) I plan on buying an Atlas:
Bob Parker also made a ring tester for flyback/inductor testing (anatek also sells it) and the schematic is on the web, I do not "really" need one but am planning on building one just to try it out....and because I have a tiny project box with a strip LED already mounted on it in my junk box |
That Atlas is a nice looking unit. The only thing I dont like about it is the alligator clips since most ESR testing is done in circuit and this would be more difficult to attach as there is not always something to attach to or if its an SMD. I guess you could clip something in there like a paper clip or another test leed, but I'd want to be sure that it didn't add to the ESR results. Unless it has a zero test like the Cap Wizard.
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jask
Joined: 17 Mar 2006
Posts: 10187
Location: kamloops BC
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| Posted: Sun Dec 20, 2009 6:44 am Post subject: |
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they all have some kind of probe compensation method, some of the "beepers" let you adjust the beep set points as well.
on my tester I use an old set of DMM probes with screw on clips, but I would rather have a set of tweezer probes.
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VideoGrabber
Joined: 09 Apr 2006
Posts: 933
Location: Michigan
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| Posted: Sun Dec 20, 2009 11:07 am Post subject: |
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macgyver commented on the Atlas:
> I guess you could clip something in there like a paper clip or another test leed, but I'd want to be sure that it didn't add to the ESR results. Unless it has a zero test like the Cap Wizard. <
Yes, they have a cable compensation function, and are able to read down to 0.01 ohms.
While most ESR testers will do a good job with your standard electrolytics, if you run into film caps (e.g. metalized polypropylenes, teflon, etc.) they frequently give misleading readouts (showing them bad) due to their reactive component. The Atlas units from Peak eliminate this component, and can thus test any cap (electrolytics down to ~4.7 uF*, film down to 1 uF). That's an advantage. One disadvantage of the Atlas units is that you have to trigger them each time to start a test cycle, which can be problematic if the cap you're testing has leads too short to connect the (bulky aligator) clips to, and you're using both hands to make contact. (They have a "third hand" device available, but it's a relatively expensive optional kludge.) On the good side, they also have multiple audible alerts (@<1, <5, >40, and OC), and auto-shutdown, to save on batteries.
Also, for those with a CapWizard, you might want to invest in a CapWizSaver, to avoid having to repair it in the event you connect to a cap that hasn't discharged (or a circuit where you've left the power on!). Units like the Atlas go through a controlled-discharge cycle, if they detect it's needed (up to at least 50V). You can check out their User Manual for more details on the Atlas.
For those in Canada, here's another place to find the BlueESR Tester kit that jask mentioned.
And to Mike:
> No, neither of my cap testers have ESR read out. <
Don't lament that fact. None of the multifunction testers that measure capacitance, inductance, etc. and ALSO include ESR readouts are half as good as the dedicated ESR testers.
*Like most units, these are rated for down to 1 uF, but looking at the chart in their manual, anything under 4.7 uF is going to read out >40 ohms at some voltage ratings, even on a good cap, and 40 ohms is the max for these units (unlike others that will read up to 99).
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