electrolytics: rated vs working E

[oldhippy]

greetings
back when I went to school (70's) I was taught not to operate a 'lytic too far below it's rated voltage or it's value could change or something like that...is this still the case? My reason for asking is that I have a canned multi-cap rated at 20@500v...can I use it correctly on a supply rail at only 325v?  Thanks guys!
PS
true story. when I was maybe 9 yrs old something happened that focused my attention on electronics and in hind sight, probably influenced my career choice. The TV man came to the house to fix the set, as they all did back then, tube case in one hand, tools in the other. He had the back off and was in there fiddling around when, yeah, he flew back, hit the wall adn knocked his glasses off...he hooked up real good, I guess. :-) My dad jumped up aand asked if he was alright and as he was putting his coke-bottle glasses back on, he smiled and said," sure...like the boss always tells the new guys, " If you can't take a few hundred volts, you shouldn't be messing with tubes"" wow, I thought...

[FYL]

The oxide layer is formed at nominal at the end of the manufacturing process, then reforms at the actual working voltage.

Using a 500V-rated cap at 350V is OK, it'll "adjust" to 350V conditions. If you want to bring it back to 500V, you'll have to reform it at 500V, that's all.

[loogie]

You need to watch this. 

http://www.imdb.com/title/tt0047542/

You'll see why...

[HotBluePlates]

I was taught not to operate a 'lytic too far below it's rated voltage or it's value could change or something like that...is this still the case? My reason for asking is that I have a canned multi-cap rated at 20@500v...can I use it correctly on a supply rail at only 325v?

FYL addressed your primary concern.

I think you were also remembering something different and thinking it applied here.

Aside from being advisable to operate components somewhat below their actual maximum rating, old electrolytics were often marked "500vdc 350v working". This does not mean that you can/should only apply 350vdc to the cap. What is the peak voltage of 350vac? 350v * 1.414 = 494.9v peak.

So really, "working voltage" was the amount of a.c. voltage that could be applied to the cap and still have a peak voltage within the cap's rating. It did some of the math for you.

[oldhippy]

thanks, guys
I do appreciate it...I survived the 60's AND the 70's! (insert Butthead laugh here)