2014-07-16 5:27 GMT-03:00 Gene Heskett <ghesk...@wdtv.com>: > Does this scope also measure "ESR"? That is an often overlooked > characteristic, but very real fault in electrolytic capacitors, much more > prevalent in the lower voltage stuff. The higher voltage stuff can > usually fix itself by re-welding the connections internally. Lower > voltage, under 150 volt stuff can't. > > ESR stands for equivalent series resistance. Its caused by poor > connections between the terminal leg you see, and the actual alu foil and > electrolyte soaked kraft paper that is the capacitor itself. > > The only test tool I ever found that does a decent job of measuring this > is called a "Capacitor Wizard", and sells for about 180-200 dollars on > this side of the pond. Google for it. > > It uses an 85 millivolt signal to measure the capacitors resistance to a > 100 khz signal, and anything over 2 ohms was either bad or going bad next > week, change it. 85 millivolts so it didn't "fix" the bad cap. 100 khz so > it largely ignored the size of the cap until you were down to less than 2 > u-f. > > When I was the engineer fixing stuff at the tv station, it found bad caps, > in circuit, in digital circuitry, where the average cap is the size of a > pencil eraser, surface mounted, by the 3 lb coffee can full. It was the > single most valuable tool I had to keep about 20 DVC-PRO video tape > machines running well. >
Hello Gene and thanks as always for your experience and help! I really don't know if it's capable of measuring ESR, but I'll check that in the Fluke's website since we don't have the oscilloscope here. I will check about that Capacitor wizard, or anything similar here in my country, if not I can look for circuits too, the fastest the better. I have a signal generator too, I don't know if I can use it in conjunction with the oscilloscope to test them. The other idea is to replace them blindly to take the chance and see if that solves the problem. It's a good possibility for the caps to be bad because the failure was coming and going. There were days when the alarm tripped, and yesterday was the worst case, but between failures the lathe worked. I suspect the thyristors of the drive like any other semiconductor can't behave like this. The only thing I know that can agonize like this are capacitors. This might sound stupid, but my PC monitor wouldn't turn on some times, and after a minute the monitor by itself turned on. After a while behaving like this the day came and the monitor never turned on again. The light blinked in a different frequency of that one it's suspended. I opened it and there where two electrolytic caps a little swollen. I replace them and the monitor is still working. I hope that's it, because if not I have to figure out how to make it work at least at constant speed (600 rpm more or less) to make it work since I only do rough cuts with the lahe, and all the finishing is made on grinders. -- *Leonardo Marsaglia*. ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
