Capacitor leakage tester/ checker - Page 1
Forum section: electronics / repair

author: diydidi
author_rank: Contributor
timestamp: November 01, 2016, 06:01:39 pm
content: HiI want to build a capacitor leakage tester/ checker instead of buying something expensive.I was thinking of using my variac, followed by a voltage doubler to reach about 700V DC.I'm not sure how to do the metering. I could either use a 50uA moving meter in series with a 10k resistor followed by the cap under test, or I could measure the voltage across the cap instead of the uA meter keeping the series 10K resistor.I'm open for ideas and if any one has a better layout, please share it with me.Thank you!

author: Seekonk
author_rank: Super Contributor
timestamp: November 01, 2016, 06:19:10 pm
content: I built a MOV tester for production and used a 120V isolated winding of a transformer and a quadrupler or more to get a high enough voltage at very low limited current. I can see driving a 12V winding pulse width to get the desired voltage you want. Use a resistor to measure the current, protected by the voltage drop of two diodes in parallel. This will limit the maximum voltage of your sense circuit. Feed that into an op amp that drives your meter.

author: Fraser
author_rank: Super Contributor
timestamp: November 01, 2016, 06:21:33 pm
content: Your proposed design sounds dangerous.A Safer option would be to repurpose a much safer and cheap CCFL or EL driver board to create your 700V DC. Current monitoring may be a suitable ammeter but I would opt for p.d across a series resistor so that an oscilloscope may be used to monitor any momentary leakage.Some thought is needed for circuits protecting the Multimeter or Oscilloscpoe from a damaging high voltage event.Fraser

author: kripton2035
author_rank: Super Contributor
timestamp: November 01, 2016, 06:46:05 pm
content: one example here :http://kripton2035.free.fr/LCR%20meters/lcr-capaleakmete.htmlor here :http://kripton2035.free.fr/digital%20esr/esr-sprut-de.html

author: Ian.M
author_rank: Super Contributor
timestamp: November 01, 2016, 07:07:51 pm
content: Another key area that you have to get right is quickly and effectively discharging the capacitor under test at the end of the test, and reliably indicating it has discharged to a safe voltage.

author: Johnny10
author_rank: Frequent Contributor
timestamp: November 05, 2016, 10:06:09 am
content: I know your interest is in building your own... but I have restored one of the Heathkit IT-28 Cap and leak detector. They are very inexpensive. Work great. Checks Leakage to 600 volt.http://www.ebay.com/itm/Heathkit-IT-28-Capacitor-Checker-/201681713037?hash=item2ef52ab78d:g:5zgAAOSw8w1X8YuaAlso schematic easy to find.Or use for parts.

author: PA4TIM
author_rank: Super Contributor
timestamp: November 05, 2016, 05:33:19 pm
content: http://www.pa4tim.nl/?p=1385A variac is not a great Idea because of safety.I made a page about DC leakage, there are also a few schematics. They are very easy to make.For voltage over 450V I use an old HP PSU that was made for photomultipliers but you can use a transformer like they used in tube equiped stuff. Because we have 230VAC and 450VDC is more then enough for me I used two transformers with the secundairs coupled.

author: kripton2035
author_rank: Super Contributor
timestamp: November 05, 2016, 05:57:03 pm
content: siliconchip made a capacitor tester and reformerhttp://archive.siliconchip.com.au/cms/A_112073/article.html