E-cap ?

[shooter]

does it matter for longevity whether you store electrolytics open or shorted?

[shooter]

thanks, they are cool, dry and dark, just was worried they'd build up a charge over time and they are BIG, 10,000uF @450vdc.

[Paul1453]

Is anyone in need of some new multi cap cans?  I've got quite a stock of them now and would be willing to part with some of them at very reasonable prices.  If so PM me and let me know what you need and what you'd be willing to pay for it including shipping.

[sluckey]

Big caps like that could possibly build up a charge. Don't know for sure. Might be a good idea to put a strap across caps of that size when storing.

I worked with a big 150 pound PFN (pulse forming network) that's basically a taped coil with a cap from each tap to case ground. The spares were shipped from the depot with a heavy duty strap across the terminals and a warning about dangerous voltage buildup if the strap was removed. Also a request to put the strap on the defective PFN we were returning. I had no reason to think this was bullshit!

The PFN is the big thing sitting in the lower right side of this transmitter cabinet. It has two silver balls on top.

[shooter]

two silver balls on top

spark gaps? 
the radar I worked on, when they went off, sounded like a shot gun!

strapping them up!   they aren't the big 'ol metal type, just big mallorys, but way to cool to pitch.

[PRR]

> store electrolytics open or shorted?

I've never heard of that.

Electrolytics normally leak plenty, won't "accumulate" any dangerous charge.

> a big 150 pound PFN ...shipped from the depot with a heavy duty strap across the terminals

That is different. They are film or oil caps (very low leakage). At the factory a high voltage is put across them to test. In use, hi-volt again. You discharge with your 4-foot screwdriver, OK..... except dielectric absorption means some charge is slow to bleed off.

Ever run your car or flashlight battery down, waited some hours, and found a little crank/light in it now? Capacitors do a similar thing.

Put a voltmeter on an amplifier's 350V supply, bring it up, turn-off, discharge to <1V, remove the discharge, wait. Over a period of minutes the caps may rise to 5V, even 10V. (Which can confound "power-off" ohm meter tests.)

This low absorbed charge will not hurt the caps. I've never seen it remotely large enough to be a danger.

The PFN peaks at, what? 30,000 Volts? This suggests 500-1,000 Volts after a quick discharge and some time to recover. This is dangerous. Even if it is only a little 3,000 Volt PFN, the recovered voltage could be high enough that the company does not want the liability.

> two silver balls on top.

That and the insulator says this is no weeny 3KV device.

[Paul1453]

Is anyone in need of some new multi cap cans?  I've got quite a stock of them now and would be willing to part with some of them at very reasonable prices.  If so PM me and let me know what you need and what you'd be willing to pay for it including shipping.

Here's my current inventory.  If you see something you're interested in PM me.

[Paul1453]

More new caps.