Capacitor gives shock during charging

[gmphadte]

I was reviving old capacitors. They are 8700µf/150V. Being old, their size is quite large. They r like beer can but bigger in height.

I had connected 34 volts and were charged to that much volts only. I accidentally touched across the cap with my arm and I could feel the tickle. The PSU was ON and connected.

How could I get the tickle when it is only 34 volts...!!!

Gajanan Phadte

[wintermute]

Ever lick a 9V battery? Doesn't take much voltage to feel it if the part of your body you touch it with conducts well. Were you sweating? wet skin conducts a lot better than dry!

Tony.

[gmphadte]

This was not that dc shock.

when I left only one probe of my DMM connected, it shows variable activity and its bar and display go over range, but not steady.

Gajanan Phadte

[DF96]

Measuring with only one probe from the DMM is a well-known way to interact with unphysical entities. In this case I suspect that you have woken up the gremlins. These live inside capacitors. What they are supposed to do in electrolytics is repair the oxide layer (a bit like replastering a wall) but sometimes they are lazy so if the capacitor is not used for a while they go to sleep. Unfortunately when woken up they can be grumpy. Instead of repairing the oxide layer they sometimes poke holes in it instead, or play with your DMM.

I suggest you let them go to sleep again, then wake them up very gently by reforming the capacitor very slowly. Always use both probes from your DMM, as this confuses the gremlins and stops them from playing with the readout.

[gmphadte]

Gremlins- yes I believe u. LOL

When i found that the DMM is jumping around, I knew it is some activity inside the capacitor. This can be due to the inductance of the cap. After all they r quite big.

I was not measuring but the neg lead was just cliped on to the cap, for no specific reason.

Gajanan Phadte

[digits]

A 35V charge on a cap, is quite a hard shock, its quite fun to toss a 35V charged cap from a gainclone at a friend and watch the supprise on his face when he gets shocked.

[CBS240]

...At least you didn't have it charged to full capacity...150VDC would hurt badly. This kind of accident around a 400V valve circuit and your likely to be pushin up daisys.




Thats an advantage of solid state, you can afford to be less careful.

[amptech]

35 volt shock...not good! use a 100 ohm resistor across it to drain the charge...