I'm surprised you haven't found more defective input caps. If you're pulling max current, those caps work hard. This is a peak charge circuit. That means the capacitor ripple current is very high. Charging current is limited to the peaks of the ac sine wave.
Say you got a converter delivering 1000W. You think the ac current is:
I = 1000W / 120V = 8.3A rms, or 11.8A peak
However, the peak current is considerably greater than 11.8A due to the power factor of perhaps 0.7.
Peak current is actually about 11.8A / 0.7 = 16.8A (or more).
Perhaps the reason you're not seeing more input cap failures is because most supplies don't operate at max power too often. The PD never gets to max power.
KJINTF wrote:
Very seriously doubt if the primary side large 820ufd @250Vdc caps will cause you any grief. They should be rated 200Vdc or higher since the peak value of the 120Vac RMS voltage is what is applied to them which is typically 170Vdc.
Many of the units have 450Vdc rating to accompany the 240Vac market.
I have had well over a hundred converters apart for repairs and only found the primary side filter caps bad in less than 5 units. They are used in a simple filtration application where ESR is of limited concern.
