ESR meter - In circuit capacitor testing?

[Diabolical Artificer]

Got to be worth a go Rob, you havn't got much else apart from taking lots of voltage readings and careful study of the circuit. My understanding of electronic circuits is still a bit sketchy, so I struggle with the logical considered approach to an extent and go for a more random test this, test that, poke it with a stick, that looks odd approach.

So if like me, you need all the help you can get especially on something as complex as a VCR, get a cheap one and try it. An ESR meter aint a magic wand though.

The one above looks ok at about 50 sheets and Argus25 knows his onions, I'll be bookmarking it for when I have some spare cash.

Andy.

[Sideband]

We used an Argus25 when a mate of mine had his own business and I used to help him out on Saturdays. I had the task of building it and can confirm it was superb...we used to whizz through VCR power supplies and later the LCD sets that had failed after about 13 months. Brilliant piece of kit.

[mhennessy]

Originally Posted by collisr

I see above that mhennessy said the Grundig V2000 used a switched power supply - I didn't know that - does this apply to my model? And if so, what difference could that make to my diagnosis?

Mine is one of these: https://www.oldtechnology.net/images...ig2x4super.jpg

I don't if the other models have a switch-mode PSU, but that one definitely does.

The clue is the transformer. A large and heavy iron affair means linear, whereas a small transformer using ferrite is a strong indicator. Also, what is in-between the mains input and the transformer? If there is active circuitry (transistors, etc) before the transformer, then it's a switcher. A linear PSU might have little more than a fuse and a power switch between the incoming mains and the transformer. You might find some filtering on better supplies.

A further power supply sub-class involves a heavy 50Hz transformer, but once the low voltage DC rails have been established in the usual way, the voltage regulators could be switched-mode DC-DC converters, which avoid the need for large heat sinks. The thing to look for is an inductor. For an example of these, just look at a PC motherboard. Outside of the obvious things (CPU, RAM, PCI slots, large chips), most of what you see on a modern motherboard is related to power supply.

Another trap with in-circuit ESR tests:

Capacitors are often in parallel. If so, the bad ones will be hidden by the good ones; 0 ohms in parallel with infinity ohms is 0 ohms . It might not be obvious, as a PSU rail will typically have many capacitors in parallel, spread out all over the place. And as well as electrolytic capacitors, designers will put low-value capacitors (perhaps 100n) in the mix as well. A 100n non-electrolytic capacitor will have a low ESR.

The fault you describe could be the power supply, but it might not be. There is a lot of complexity in those machines, especially in the servo and control circuits that drive the motors. Statistically, I'd expect the fault to be in there rather than the PSU, but because the servo circuits are complicated, I'd eliminate the PSU first of all. To do that, you need to monitor the supply rails and see what they do when the motors start. If they fall appreciably, then that might be an indication that the power supply is unable to supply enough current to the motors. But of course, it might also be an indication the motors are drawing more current than they should! It's a chicken and egg situation. So the best way to check the PSU is to swap in a known-good PSU from an identical machine. Not always possible, admittedly...

As well as seeing how much the rails might "sag" under load, I'd also want to see how much ripple is on the rails. For this, you need an oscilloscope (have you got one?). As capacitors age and their ESR rises, the ripple rises with it. Some circuitry couldn't care less about this, but a lot of circuits will be deeply unhappy about it.

It's been more than 20 years since I last played around with V2000 machines, but back then, the PSUs failed by blowing up - and were not easy to fix. Early switched-mode power supplies tended to fail spectacularly with almost no provocation, and to fix them, you basically had to change every bit of silicon in there and cross your fingers and pray to the power supply gods! Today, the designers have got much better at avoiding that (and the silicon bits are generally a lot better), so power supply faults tend to be worn out capacitors or start-up faults (often just one resistor). If someone brings me a power supply that has blown up, I walk away if I possibly can!

Cheers,

Mark

[Argus25]

Originally Posted by joebog1

Is Argus involved with Silicon Chip?

I'm not connected with Silicon Chip magazine in any way, except that in the past they were kind enough to publish a few of my circuits and vintage radio articles that they thought were worthy. Also they published my design for a spark energy meter that they turned into a kitset. I didn't design that ESR meter, but it is one of those things I wish I had ! So I am merely a subscriber to their great magazine and occasionally a contributor.

[red16v]

I spent many years repairing broadcast video kit down to component level - so as you can imagine audio/video/analogue/digital. One of the most useful bits of kit we bought were two ESR meters made by ‘Capacitor Wizard’. Not cheap, but paid for themselves many many times over in terms of saving time and energy when testing in circuit capacitors.

Some reviews have complained about their build quality but we never experienced any problems and they had a lot of multi user ‘rough’ handling over the years. They also had built in fuses in series with the test leads for those odd occasions when the capacitor was not discharged when you prodded it. That’s an important point and I would look for an ESR meter that either had protection or an automatic discharge circuit prior to measurement built in. The UK suppliers (can’t remember their name after all this time) also sold a fuse repair kit as a stock item for those occasions when the fuses did what they were supposed to do!

It all came down to experience when interpreting the meter display and there is no substitute for that. A good 100uf cap and above - expect fsd, a good 47uf cap - expect 2/3 fsd, a good 10uF cap - expect half fsd, Just examples and not at all definitive, experience is all. It saved us so much time and effort, it really really did. It was expensive but cost was not a problem in a professional environment. I appreciate are very likely to be on a much smaller budget. Good luck.

[evingar]

Originally Posted by Argus25

Putting aside any pros & cons on the theory of ESR meters and the utility value of having & using one, if you are going to get one there is really only one type in the world that I would recommend.

This particular meter applies a very small low amplitude pulse to the capacitor under test, good for in circuit testing. It can also be used for low resistor values. I have compared it in my workshop to a number of other types of ESR meter, including ones which use sinewave currents and using other methods with generators & scopes to assess the ESR. I wouldn't use any other ESR meter, this one was beautifully designed and conceived and despite being a kit, its has a very professional painted and screen printed steel front panel and a very solid case and easy to read LED display.

I'm a very critical judge of test gear, I liked these ones so much I bought two of them. It has become an indispensable weapon in the war that I wage against against defective electrolytic capacitors, which are the nemesis to longevity of all electronic equipment. In general I check the capacitor for value, leakage at its operating voltage and ESR to decide if its ok, or not.

http://www.altronics.com.au/p/k2574-esr-meter-kit/


Photo of one attached.

I take it it's another vendor of the Bob Parker design.


It Looks identical to the like old old Dick Smith version :-

http://bobparker.net.au/esr_meter/esrmeter.htm


If so, yes, I fully endorse it, I have 2 - oner from Anatek and one from a guy in Portugal :-

http://clientes.netvisao.pt/greenpal/information.htm


The nice thing about them is you can just go round dabbing the leads on, unless you have a 3rd hand grafted onto your forehead having to press a "Test" button is a right royal PITA !

[Diabolical Artificer]

"It all came down to experience when interpreting the meter display and there is no substitute for that. " True, the DIY ESR meter I mentioned way back has an analogue meter which shows behavior that a digital meter can't. For instance most good caps cause the needle to go to FSD pretty quickly, but with some bad caps the meter will rise slowly, or dance about.

One other useful bit of kit for sniffing out bad components is a component tester such as the Octopuss, it shows a V/I curve on a scope screen, this with experience can find iffy parts quickly and save loads of time. They are easy to build too.

Andy.

[collisr]

Hey mhennessy,

My V2000 player is indeed the same as yours. And thanks for providing the observations of switched vs linear power supplies.

You (and the community) have confirmed what I guess I already knew - there is no easy way of identifying bad components in 35yo electronics - it comes down to experience, gut instinct and knowing when to use which test equipment and how to interpret the results of said equipment.

Yes, I do have a digital storage 'scope which has been great for actioning the adjustments listed in original service manuals. When it comes to diagnosing the faults I am seeing on "dead" machines, my challenge is knowing the best tricks for tracing along voltage rails, video signal paths and the like to find the bad cap/transistor etc. I still feel like I am missing some "trade secret".

I am feeling I need to push through the knowledge barrier I am facing as a (relative) noobie before investing in the ESR meter. I can appreciate it will help me when faced with a multitude of potentially faulty caps but I need to isolate where my problems are first - which as you say can be tricky.


I have tried to avoid the "replace random boards until it starts working again" approach, because I want to use some logical reasoning, test tools and the schematics to deduce the problems. I may have a long way to go...

R.

[ms660]

There's no trade secret, it's a mind set, nothing much more than that, you have the extensions to go with that, your scope, a multimeter etc. A schematic is also essential unless you just want to keep on changing bits 'till something does something.

Lawrence.

[Diabolical Artificer]

When I can't fix anything I put it away A) to stop me getting too wound up/frustrated and B) in the hope that when I open it up again, I'll know a bit more. This has worked on a few things, but there are a few miscreants who won't be fixed, manana manana.

To help yourself, take loads of pics before you touch it so you know how it should go together, keep good notes and don't just scrawl down a load of figures (guilty) and leave notes to yourself telling your future self what you checked etc.

Lastly, info has never been easier to obtain, on technical subjects that is so read as much as you can and get the breadboard out so you can translate info in books to experience. Most of what I read may as well be gobbledegook, but bits stick, eventually. : )

Good luck, A.

[WaveyDipole]

If you were thinking of buying a Peak Atlas ESR70, then there is currently a 20% discount on some of their test meters:

http://www.eevblog.com/forum/buysell...forum-members/

I have no affiliation with Peak, just chanced upon it the other day while researching ESR and LCR meters.

[ColinTheAmpMan1]

I think this is well and truly expired - the original date was October 16th 2017. I have been keeping an eye on Peak's website for a repeat of just such a discount. I was hoping there might have been some kind of "January Sale" but not so far...
Colin.

[Goldie99]

I tried the 20% code earlier today - it still works fine, at least up to the checkout point (I didn't complete checkout).

Alan

[chriswood1900]

RADCOM10 will get you 10% from Peak.

[karesz*]

Hello Rob,
I think its a good way to read some articles from PA4TIM too, explicite ESR meter & Leakage tester...
Have succcess! Karl

[WaveyDipole]

From my own research I can recommend these two threads:

https://www.eevblog.com/forum/beginners/esr-meter/
https://www.eevblog.com/forum/beginn...trolytic-caps/

I found them both an interesting read on the subject. PA4TIM contributes to the second one. Perhaps the key lesson I took from these was not to rely on in-circuit test results.

[ColinTheAmpMan1]

Originally Posted by ColinTheAmpMan1

I think this is well and truly expired - the original date was October 16th 2017. I have been keeping an eye on Peak's website for a repeat of just such a discount. I was hoping there might have been some kind of "January Sale" but not so far...

Well, I feel rather red-faced because Goldie99 is quite correct; the eevblog code does still work! I have ordered an ESR70 from Peak and paid £72, including £4 postage. Nice deal, I think.
Colin.

[FrankB]

Red16D nailed it with the Capacitor Wizard.
I bought one and the mod kit (To keep from damaging the unit with a charged cap.)
It has a FULL schematic with it and all "field" replaceable parts too. Unlike the competitors I saw.
It paid for itself in profit from the first 2 weeks I used it. A killer for bad caps in TV's & stereos.
If you are in doubt of a reading, compare the suspect caps readings to a new one.
I did find that the 1.0 mfd and .1 mfd 'lytics tended to read high on the scale, even new ones.
It is also great for an audible continuity tester.
My 2 cents worth.

[WaveyDipole]

Hmm, at the current price of $199 that seems rather expensive for what it is when you have a look at the teardown in this thread:
http://www.eevblog.com/forum/testgea...-few-pictures/
Still, the OP's question was whether ESR can be tested in circuit. I provided the link to the Peak because at the time I was interested in this question myself and Peak claims their tester can do this. However, having read up as per the various links above I am now convinced that relying on results from testing in circuit is not a good idea. In the case where there are multiple caps in parallel it would be impossible to make a determination without disconnecting individual caps. Although in SMPSU's ESR is of critical importance for some caps, it is not the only factor that determines whether a cap is bad. It seems to me that an ESR meter may be a quick way to identify possible suspects, but the cap would still have to be removed to confirm. The more worrying part though, is that some caps might be identified as good when, in fact, they are not, because an inductor or low value resistor might be affecting the reading. Another factor is that ESR tables, although giving a general indication, may or may not be correct for the manufacturer and product series under test so it is a good idea to check data sheet. This seems to be particularly the case for caps in older equipment manufactured at a time when ESR was not such a big issue and for which the tables are likely to be mis-leading.

I have one of these cheap far east component testers which also shows ESR and so far have not purchased a Peak ESR meter as I don't think for me as a hobbyist it will any value.

My apologies if my comment sent this thread in the wrong direction.

[Argus25]

Originally Posted by ColinTheAmpMan1

I have ordered an ESR70 from Peak and paid £72, including £4 postage. Nice deal, I think.

The outstanding ESR meter (Bob Parker type) that I suggested in post #19 is only 50GBP, sure it's a kit but it's fun to assemble. And of note, the applied voltage and current is very low so that it gives more reliable results than most ESR meters for in circuit testing.

Actually using it, there has not been one occasion where it has given me a significantly different reading comparing an out of circuit test, so low R's and L's have not caused issues and that includes many repairs of switch mode PSU's and lab instruments like oscilloscopes.

Admittedly all ESR meters lose their value for in circuit testing if capacitors are in parallel, that is one thing we have to accept and disconnect at least one lead of the capacitor under test, but the fact is the rest of the time, which is "most of the time" a good ESR meter is an invaluable tool, so looking for a plethora of technical reasons or caveats not to use one is like wanting to go fishing without any bait.

Also, we understand that the ESR's of older capacitors may not be as low as more recent designs, but that does not make them unserviceable in their original application. Hopefully the OP will understand this.

I submit that if folks have had bad experiences and difficulties with ESR meters for in circuit testing, likely it is a poor design ESR meter they have, and they should get a better one, like the one in post 19 .