On 07/16/2014 02:16 PM, Leonardo Marsaglia wrote: > Well. I took up one of the capacitors and the label says the following: > > HCGFA > 1800 MFD 450 VDC > SURGE 500 VDC > POSITIVE + > > Here is an ebay link that shows the actual capacitor that I have. > http://www.ebay.es/itm/HCGFA-Capacitor-1800-MFD-450-VDC-Surge-500-VDC-Used-/120838813902 > > There are several models on Digikey that have the same capacitance and > voltage ratings, but I don't know if theres anything else to check. Make sure the spacing between terminals is the same, and it should fit fine. > Visually inspecting the caps, they look ok, they don't seem to be swollen > or anything, but I guess that doesn't tell anything. > > Sometimes a deteriorated cap is plainly obvious, sometimes there is no visible sign at all. You could charge the cap to some voltage and observe the rate at which it drains. For 1800 uF, with a 10 K resistor, the voltage should fall at an exponential rate such that it reaches 36% of the initial value in one time constant. One time constant would be .0018F * 10K Ohms = 18 seconds. So, if you charged it to 10 V, in 18 seconds it should fall to 3.6 V. If it falls to zero in a couple seconds, that is a clear indication the cap is dead! Sometimes, they can develop high internal series resistance, so another test is to charge it to 10 V or so, and then short the cap with a bit of wire. If there is no spark at all, it would indicate high series resistance.
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