Quote:
Originally Posted by DaveWM
What I would really like would be a test setup that I could program to step up the voltage based on current, say have it ramp up to try and maintain a set constant leakage current (selectable), then graph that voltage over time and set the max voltage to end the test. The resulting curves would be fun to examine.
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I threw together what you described above from Radio Shack stuff. It uses an Arduino Uno and a pulse width modulated motor controller to drive two 12.6V to 120V filament transformers to step up to 240VAC. Then a voltage quadrupler. This results in a programmable 6-900 VDC supply, The Arduino software reads the analog inputs to raise the capacitor voltage while limiting the current and max voltage, and then monitoing the current decline to the required minimum current. Anyway, here are some plots from four capacitors. I set the current limit to 5 mA, and the voltage limit to the cap working voltage. The first cap is a 630TS 40uF 450V, the second a Sprague 16uF 450V cap added as a repair, the third a 630TS 80uF 150V cap, and the last a Nichicon 82uF 450V cap. My Sencore LC75 says the RCA caps show a lot of dielectric absorption, the Sprague is toast, and the Nichicon was the best (of course, its new) but did also show some dielectric absorption. I thought it would be interesting to plot the computed power going into the cap as well as its computed effective resistance along with the measured voltage and current. Although its now controlled through USB, it could be standalone with the addition of a small two line LCD panel and some switches. I think I could save some of my 630TS caps, but some are completely unresponsive to reforming.