i worked as an amp test tech for a manufacturer, and the amp had these 15000uf/75V caps in the power supply. one time we had a "newbie" working in assembly, and he was getting 50% of the caps backwards. the first one of these amps i got at my test station, failed the power up test on the variac, where i slowly turned up the variac and watched the ammeter. this amp pegged the ammeter at 10V. i checked all the usual stuff, and couldn't find a shorted rectifier, output transistors, wiring, etc... so after about an hour of checking stuff, i did the "show me where it hurts" test (power it up with no variac and see where the smoke comes from)..... both of the big caps went off spewing smoke like smoke grenades. after checking the day's production from the assembler, i found about half the caps in backwards, and the assembler didn't know they were polarized (or had been shown and forgot).