Help with tools - Page 1
Forum section: electronics / beginners

author: fa2ality
author_rank: Contributor
timestamp: December 22, 2011, 06:32:39 am
content: I'm a computer technician by profession and I'm interested in expanding my expertise as I get a lot of dead motherboards. I want to start probing laptop motherboards, most of them are no power issues.I was looking at Dave's review of Smart Tweezer and I'm wondering if that is better or a decent Fluke multimeter, if the later, which model?Also I would like a good in circuit capacitor tester as I get a lot of dead power supplies (laptops and desktops) and I'd rather repair them by changing capacitors as I noticed the problem is usually bad capacitors. I was looking at thiseBay auction: #190592707151and wondered if it can handle desktop power supply capacitors?Thanks in advance, your videos are worth their megabytes in gold.

author: samgab
author_rank: Frequent Contributor
timestamp: December 22, 2011, 07:12:11 am
content: I'm pretty happy with the Fluke 87 V. I'd say it would be more than capable for your needs.It measures capacitance reasonably well, with an accuracy of ± (1 % + 2 LSD).

author: fa2ality
author_rank: Contributor
timestamp: December 22, 2011, 07:19:50 am
content: Thanks for the fast replycan i test them while in circuit?

author: samgab
author_rank: Frequent Contributor
timestamp: December 22, 2011, 07:42:22 am
content: Quote from: fa2ality on December 22, 2011, 07:19:50 amHopefully someone more knowledgeable about this particular field will field this question.I usually use my 87V to measure caps in circuit, and it has always worked for me,but I don't know if there's a reason not to do that?

author: kripton2035
author_rank: Super Contributor
timestamp: December 22, 2011, 07:45:14 am
content: yes you need an esr (dcr) meter like the oneint the ebay link.but that's one of the most expensive esr meter that exists (even if it's a very capable one !)take a look at my repository, you will have a list of commercial meters, or to build yourself easylyhttp://kripton2035.free.fr/esr-repository.htmlbtw, the fluke 87 can measure the capacity, but CANNOT measure the esr of the capacitorsit is quite easy to measure esr in circuit by using a measuring voltage less than 0.5Vbut the measure of capacity in circuit is difficult besauce it depends of all the other capacitors in the pcb.

author: EEVblog
author_rank: Unknown
timestamp: December 22, 2011, 07:51:59 am
content: A multimeter or simple LCR meter is not suitable for in-circuit testing. What you need is a proper ESR meter.That BK Precision one should work a treat.Cheaper options are available though.http://members.ozemail.com.au/~bobpar/esrmeter.htmhttp://www.peakelec.co.uk/acatalog/jz_esr60.htmlDave.

author: EEVblog
author_rank: Unknown
timestamp: December 22, 2011, 07:54:20 am
content: Quote from: kripton2035 on December 22, 2011, 07:45:14 amThe specific resources and knowledge available from EEVblog forum participants never ceases to amaze me!Dave.

author: samgab
author_rank: Frequent Contributor
timestamp: December 22, 2011, 08:04:42 am
content: Quote from: EEVblog on December 22, 2011, 07:54:20 amHa, I noticed one of the linked attachments (http://www.midwestdevices.com/pdfs/Tnote3.pdf) is written by a "Doug Jones"... Any relation? Of course, not that it's a common last name at all...

author: BravoV
author_rank: Super Contributor
timestamp: December 22, 2011, 08:07:21 am
content: Quote from: EEVblog on December 22, 2011, 07:54:20 am+1 , thanks to Kripton for his hard work & dedication, believe that is the most complete esr meter circuits collections and repository on earth.Imo, it deserved a place in your bookmark.

author: kripton2035
author_rank: Super Contributor
timestamp: December 22, 2011, 11:45:40 am
content: :-]thanks for the compliment(s) !will try to improve the site by building all(most) the meters that are described ...but takes time...

author: ipman
author_rank: Regular Contributor
timestamp: December 22, 2011, 04:07:52 pm
content: You should know that an ESR meter will test capacitors in-circuit ONLY IF THEY ARE NOT IN PARALLEL. Otherwise, it may trick you.The Blue ESR meter is a good tool, but expensive. There are other cheaper variations tough.

author: The_Penguin
author_rank: Regular Contributor
timestamp: December 22, 2011, 08:14:22 pm
content: Quote from: kripton2035 on December 22, 2011, 07:45:14 amThe Russian one second from the bottom - the ESR Micro 4 is awesome!I bought mine from a U.S. source prc68.comhttp://www.prc68.com/I/ESRmicro.shtml#P

author: Simon
author_rank: Unknown
timestamp: December 22, 2011, 10:17:36 pm
content: ideally you should remove any component from a board for any test (or get one leg off) as you have no idea of the effects of other connected parts. I used to check resistors onboard when i was pulling stuff apart and it generally worked but i never relied on it for more than identification.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 22, 2011, 11:50:19 pm
content: Its true there is always the danger of a false reading from in-circuit measurements, but there is a big difference. Testers designed for in-circuit use have excitation voltages < 100 mV or so (maybe 200?). This avoids forward biasing diode junctions enough for them to turn on (much). This basically makes all the silicon in the circuit an insulator, and you get mostly the parallel impedance of the passive elements connected across those nodes. It would be of little for a complex analog filter (without extra interpretation), but for many applications such as pull up/down resistors, impedance matching / terminating resistors, AC coupling caps, SMPS inductors, and more you will find that one or both terminals of the passive device are connected exclusively to ICs. An ordinary LCR meter that used 1 volt excitation on the other hand would be essentially useless.Obviously the tester is much easier to use with confidence if you have a schematic and a layout diagram sitting in front of you than if you are poking around in some circuit trying to figure out how it works. It is even better if you are trying to troubleshoot / autopsy at broken unit when you have a known good board to compare it to. Then even wonky readings may have some value.

author: Simon
author_rank: Unknown
timestamp: December 23, 2011, 06:58:11 am
content: well that's interesting, had not thought of using sub diode junction voltages, I guess that opens up more possibilities

author: fa2ality
author_rank: Contributor
timestamp: December 23, 2011, 07:09:47 am
content: Will it be a good idea to cut short and get an oscilloscope like the famous "Rigol DS1052E" and learn my way on it. Is it complicated to test ESR's or can it even test in circuit capacitors? What can and can't this model do? Again I'm only probing desktop and laptop computer components.My cheap multimeter died and I'm planing to spend a couple of hundred $ on a replacement tool/s.Thanks everyone for all your advice.

author: Simon
author_rank: Unknown
timestamp: December 23, 2011, 07:14:32 am
content: you will need additional equipment like variable oscillators to do the test if you use an oscilloscope, it will take longer and be quite fiddly, but probably possible.

author: fa2ality
author_rank: Contributor
timestamp: December 23, 2011, 07:22:06 am
content: I see so yeah too early for an oscilloscope.I keep going back to to these smart tweezers, I know they are a little over priced but they seem to be perfect for probing on two identical boards to compare. Today I had a backlight problem on a laptop and it wasn't the screen inverter, it was from the motherboard. I had an identical laptop I could have compared the frequencies of the components between the two motherboards.Plus the blue ESR tester that Dave recommended for power supply jobs.

author: kripton2035
author_rank: Super Contributor
timestamp: December 23, 2011, 07:32:17 am
content: Quote from: fa2ality on December 23, 2011, 07:09:47 amimo, the process of measuring the esr with a scope is nice, but not very practicle...you will never take the time to connect the scope, the frequency generator, the cables, the device under test each time you get a suspect capacitor in a circuit...you'd better have a small handy device like the smart tweezers , to test iton my repository, you have the analog esr meters, with simple results on a bargraph that are really enought for thisI build the poptronix one years ago and it save many many boards trust me !!!!it costed me almost nothing as they were drawers junk components I used to build ityou rarely need to have the exact value of the esr in ohm, and if you need it you will surely have to remove the component to measure it precisely.

author: Unknown
author_rank: Unknown
timestamp: December 23, 2011, 09:26:12 pm
content: Measuring ripple on power rails is another way to see the effects of increased ESR. Not much help if it's a switcher that fails to start due to ESR, though.

author: ipman
author_rank: Regular Contributor
timestamp: December 24, 2011, 10:52:01 am
content: Allmost all good ESR-meters have a test voltage of 0.6V or under, at around 100kHz. Going below 0.2V will be a good ideea, but the will loose the capability to measure a wide range of resistance.