How do I make a leaky capacitor ? - Page 1
Forum section: electronics / beginners

author: Hextejas
author_rank: Frequent Contributor
timestamp: June 26, 2018, 03:21:41 pm
content: I made a project from Mr. Carson's Patreon site and it tests for leaky capacitors. Well, it seems that all the capacitors that i have are new, hence they don't leak. In an effort to try and make a leaky capacitor, I tried reversing the polarity of an electrolytic and puttjng 30v DC on it. I dont recommend doing that. The sucker blew up sounded like a .38 revolver. Luckily I had it covered with a rag.Anyhow, what would happen if I punched a hole in the side of a capacitor ?And I seem to remember that a leaky capacitor exhibits a resistance, so maybe I could use a resistor instead.What say you ?Thanks.

author: CJay
author_rank: Super Contributor
timestamp: June 26, 2018, 03:26:42 pm
content: You could certainly put a resistor in parallel but if you want the real deal you could also work a capacitor in high temperatures, apply voltage to one the correct polarity, heat it up and repeatedly discharge it.No idea how long it'd take to become leaky though

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 26, 2018, 04:55:11 pm
content: You could try using an electrolytic in reverse, but with a series resistor (100 kOhm or so).The reversed DC voltage wil slowly eat away the oxide layer but without spectacular effects because the energy and heating is very limited.Or limit the reverse voltage to a few volts.Or just measure the Elco backwards. Then it will probably start leaking fast.

author: Cliff Matthews
author_rank: Unknown
timestamp: June 26, 2018, 06:13:23 pm
content: Today shows Carlson resorted to his old Heathkit IT-11 (so maybe that nifty new leakage tester didn't show the whole story..)

author: BergRD
author_rank: Contributor
timestamp: June 26, 2018, 06:54:28 pm
content: Watched that video today! Like his content and the aging electronics.One thing that comes to mind is from yet another video I watched from ElectroBoom!. I'm not sure if you've heard of him and likely some here would roll their eyes at his content/videos but he's an electronics guy/engineer and using comedy and self-harm (shocks, etc) he has built quite a following as of late. I followed him initially on LiveLeak where he started but quickly jumped to Youtube and now he only works on videos.That being said, he just had a video about him making his own capacitor (Leyden Jar) which might be leaky enough to test? Simple enough to build but unsure if it helps.

author: CJay
author_rank: Super Contributor
timestamp: June 26, 2018, 06:58:42 pm
content: I think the thing with a Leyden jar is that it really isn't leaky, they tend to keep their charge an awfully long time and have some kind of self charging effect don't they (I know there's a much better explanation than that but can't think of the correct terminology right now)

author: BergRD
author_rank: Contributor
timestamp: June 26, 2018, 07:44:13 pm
content: Quote from: CJay on June 26, 2018, 06:58:42 pmCould be. Just came to mind since I had watched the video within the last hour. I will have to learn more myself about these. Heard about them over history but have never made/used. Great point!

author: innkeeper
author_rank: Unknown
timestamp: June 26, 2018, 10:17:41 pm
content: um... this may sound very silly but...why not just put a resistor across a good capacitor to simulate leakage.

author: Cliff Matthews
author_rank: Unknown
timestamp: June 26, 2018, 10:47:49 pm
content: Quote from: innkeeper on June 26, 2018, 10:17:41 pmSure a resistor would fit a linear model, but leakage can be voltage dependent. Carlson tested one of those two 450v internal transformer caps as 0.01uF with his new tester, but then his Heathkit tester found a fault at 50v.

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: June 26, 2018, 10:51:22 pm
content: Try this.Take an old capacitor that looks ok, no bulging, nothing coming out of the top and bottom. Measure it your favorite way, esr, capacitance value on the DMM. Take the capacitor and with a pair of plyers, crush it a little. Measure it again. See if the values change at all. What you will be doing is changing the physical make up inside the capacitor and causing the capacitance to change. I think you will find the capacitance value might change or not but the esr will most definitely be different.Dont do this at high voltage.

author: german77
author_rank: Regular Contributor
timestamp: June 27, 2018, 01:13:19 am
content: Most failures in electronics are due leaky capacitors. Have you consider buying scrap electronics. I once found a dead graphics card with bulky and leaky capacitors for almost free, I replaced the capacitors and since then it has worked like a charm on my computer.Or you can make an aging capacitor circuit. Discharge and charge completely the capacitor the fastest you can multiple times. A 555 with a mosfet driver should do the work. The capacitor should get warm and start to leak in matter of minutes. You even can test the quality of the capacitor by measuring it's leakage vs time.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: June 27, 2018, 01:22:41 am
content: Put a resistor and a Zener diode in series, with that combo in parallel with the cap? Then it only “leaks” passed the breakdown voltage of the Zener....??

author: innkeeper
author_rank: Unknown
timestamp: June 27, 2018, 02:17:22 am
content: maybe just put the word out for bad caps, I bet many would send you some if they have them on hand for the price of a postage stampIt's not like anyone has a use for them.

author: tautech
author_rank: Super Contributor
timestamp: June 27, 2018, 02:38:02 am
content: Quote from: Hextejas on June 26, 2018, 03:21:41 pmAll caps leak !If you can't measure it you're not trying hard enough or your equipment isn't sensitive enough.Don't believe me, use an old analog meter in ohms range across a cap.

author: jolshefsky
author_rank: Regular Contributor
timestamp: June 27, 2018, 02:56:29 am
content: Reading this, I think there may be some confusion as to the double-meaning of "leaky."Mr. Carlson's tester is for parallel resistance which will "leak" DC current. (That is, an ideal capacitor, wired in series, will block DC current—once it is charged, no DC current will flow.)Electrolytic capacitors have an electrolyte that is a liquid or goo and they sometimes leak that material out, visually indicating the capacitor is no good.

author: stevelup
author_rank: Regular Contributor
timestamp: June 27, 2018, 07:31:43 am
content: I was suspicious of Mr Carlson’s leakage tester when he first demonstrated it.You absolutely have to test for leakage at or around the operating voltage otherwise it’s pointless.

author: David Hess
author_rank: Super Contributor
timestamp: June 27, 2018, 07:38:57 am
content: Make a film capacitor using Nylon. It will have plenty of leakage which even varies with humidity and temperature.What you might want though is a capacitor with high dielectric absorption. Readthis articlefrom Pease for some ideas about this.

author: oPossum
author_rank: Super Contributor
timestamp: June 27, 2018, 11:14:07 am
content: Quote from: Cliff Matthews on June 26, 2018, 06:13:23 pmIt showed the cap was leaky using lower voltage than the IT-11Quote from: Cliff Matthews on June 26, 2018, 10:47:49 pmHis tester does not measure capacitance, Tek and Agilent meters where used for that.13:32 Agilent meter unable to read capacitance of cap while still in the transformer14:32 Tek meter reads 40.8 nF29:50 Agilent meter shows no leakage30:33 Agilent meter reads 0.019 uF (possibly incorrect due to leakage)31:37 His leakage tester show the cap is leaky (using 27 VDC or less)35:09 Heathkit tester requires 50V to detect leakage

author: joeqsmith
author_rank: Super Contributor
timestamp: June 27, 2018, 11:17:36 am
content: Quote from: Hextejas on June 26, 2018, 03:21:41 pmI was wanting to see if a simple linear model could be used to model leakage as was suggested in his video. I attempted to very carefully damage several capacitors and see how it effected their leakage. You can read about it here:https://www.eevblog.com/forum/testgear/using-low-voltage-levels-to-test-hv-capacitors-leakage-current/