Capacitor leakage testers - Page 1
Forum section: electronics / testgear

author: dcbrown73
author_rank: Regular Contributor
timestamp: September 10, 2019, 12:43:10 am
content: I have a chance to pickup an old Heathkit IT-11 capacitor checker, but I was wondering. Are these really even necessary these days when you can just outright replace the caps for relatively cheap?Is there a real reason to actually own one these days? If so, I would definitely like to know as I am considering buying it. Would it be just a piece of test equipment to own or something I might use?I hope to start restoring old radios and such.

author: wraper
author_rank: Unknown
timestamp: September 10, 2019, 01:07:17 am
content: Leakage is not something I would generally measure. Also for repairs, electrolytic cap ESR measurement is way more important than capacitance or leakage.As device itself, I would not consider it of any use other than nostalgic value/ museum.QuoteYou can but it's stupid approach. You can waste a lot of time replacing tens of caps just to find there were no faulty caps to begin with and problem is somewhere else. Also you will need to replace all of the capacitors every time if you want to be sure there are no faulty capacitors left. Faulty capacitor often may cause no apparent issue on first glance.

author: floobydust
author_rank: Super Contributor
timestamp: September 10, 2019, 03:30:13 am
content: The IT-11 is unique because it tests capacitors at up to 600VDC applied. Careful at those banana jacks... it is lethal.It can find capacitors which break down at voltage but are otherwise fine at low voltages, like old can electrolytics.Mr. Carlson's LV leakage tester only uses a few volts and has a pass/fail LED. I dislike having a number like 20uA as the pass/fail point and would like proof the caps are rejected for the right reasons. Who knows what old wax and paper caps, bumblebee caps etc. leakage should be?https://www.eevblog.com/forum/testgear/mr-carlsons-lv-capacitor-leakage-tester!-it's-finally-out!/

author: bob91343
author_rank: Super Contributor
timestamp: September 10, 2019, 04:14:25 am
content: I obtained an EICO 950B which measures leakage. However the threshold of leakage measurement is neither obvious nor controllable.So I put that instrument away, intending to swap it for something else.What I use now is a GR megohm bridge. This thing measures leakage at any voltage up to 1000 Volts and gives me a number. Actually it tells me the resistance and all I do is make a simple division to get leakage current. I do that in my head usually. Say at 500 Volts it reads 10 megohms, that's 50 microamperes of leakage. I can then decide whether that's acceptable. I can also watch it drift under test and decide whether it is increasing too rapidly with time. I multiply the leakage by the voltage, also in my head, and in the example here that results in 25 milliwatts of dissipation. Not enough to cause a problem most of the time.I would always rather have a numerical test result than a GO-NOGO such as one gets with the eye tube.

author: BravoV
author_rank: Super Contributor
timestamp: September 10, 2019, 04:30:47 am
content: If you have 10M Ohm input impedance multimeter, you could easily measure cap's leakage down to very low current level, and if you DMM have logging, you can get the interesting forming curve when testing an old cap that using this simple setup.Example of 1.5 hours forming at an old NOS polymer Sanyo OSCON cap at it's rated voltage, vertical axis in Volt that 1 Volt = 0.1 uA leakage current. Interesting curve on the first 15 minutes, and after 30 minutes.Details ->HERE

author: Shock
author_rank: Super Contributor
timestamp: September 10, 2019, 04:44:31 pm
content: This image is showing 17.6nA leakage on a picoammeter (before reforming took place) connected to a CV bench supply. With this method it was limited by max input voltage of the picoammeter.I'd use the input impedance voltage drop method Bravo suggested, it works well and if you have or make a large variable or switched range DC supply even better. Though logging is useful, if you wanted to see self healing you can also use min/max once your cap is charged or just take a measurement and be done with it.I checked the schematics and there is nothing too exciting going on inside most of those old leakage testers. Even though you can use measurement at the same time to calibrate the magic eye, it's a bit of old crusty gear that feels like you are almost tuning it to the capacitor rather than taking definitive measurements.

author: korlatos
author_rank: Regular Contributor
timestamp: September 10, 2019, 09:10:46 pm
content: You can also use the Jim Williams method, described here (look for Appendix B):https://www.analog.com/en/technical-articles/775-nanovolt-noise-measurement-for-a-low-noise-voltage-reference.html

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: September 11, 2019, 01:43:38 am
content: Sencore LC77 does leakage tests.

author: CDaniel
author_rank: Frequent Contributor
timestamp: September 11, 2019, 07:46:00 am
content: For repairing old stuff , when the cap is leaky you should see the capacitance being (way) off when checking with a modern esr/capacitance meter , so I don't think you need that tester .For lab testing capacitors is another story ...

author: mr.fabe
author_rank: Regular Contributor
timestamp: September 11, 2019, 03:17:33 pm
content: Quote from: dcbrown73 on September 10, 2019, 12:43:10 amThe Heathkit IT-11 / IT-28 is one of the useful tools to get for determining leakage and reforming capacitors at rated voltages. Your DMM will not tell you if a cap has excessive leakage. Capacitors may test within tolerance, appear normal, but will fail when running at operating voltages. A better tool would be a Sencore LC75 Capacitor Inductor Analyzer. The Sencore is near the same price point and can measure capacitance, ESR, inductance, leakage up to 600V, etc. More functions, solid state, digital readout. You can generally get by with the swap everything method for a few projects but as you gain more experience, you will be looking at instruments like these later on.

author: 001
author_rank: Super Contributor
timestamp: September 11, 2019, 09:00:55 pm
content: Cap leakage tester is WERY impotant unit to keep Your equipment biased right if high voltages applied

author: dcbrown73
author_rank: Regular Contributor
timestamp: September 12, 2019, 01:37:45 pm
content: Thanks all. I picked up an Sencore LC75 with an attached SCR250 triac tester. The only LC77's available I could find were damaged or missing stuff.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: September 12, 2019, 09:35:58 pm
content: Congrats. This one will work perfectly, I just did not know the designation of the earlier one.They have a legendary reputation especially among repair and service experts. Even as I am in the course of aquiring a nice LCR-Meter, that Sencore stays on the list. And a proper SCR and Triac tester will also come handy at a time.