ouch, zapped

[melomaniac]

depressing: friday I got zapped when I touched the volume control on my bel canto amp. and I have to say I believe something doesn't sound right since then. so, either my ears were lightly fried or the amp has grounding issues. I have not been able to find the cause of the grounding trouble. it's the weekend and I don't know what I'm going to do. before I send the amp away to be looked at, any ideas how I can narrow things down to a few most likely culprits? and how I can prevent this from recurring?

 

[dgbiker1]

Quote:

Originally Posted by melomaniac /img/forum/go_quote.gif depressing: friday I got zapped when I touched the volume control on my bel canto amp. and I have to say I believe something doesn't sound right since then. so, either my ears were lightly fried or the amp has grounding issues. I have not been able to find the cause of the grounding trouble. it's the weekend and I don't know what I'm going to do. before I send the amp away to be looked at, any ideas how I can narrow things down to a few most likely culprits? and how I can prevent this from recurring?

Two things could've happened. Either the amp is poorly grounded, gathered a charge and used you as a path to ground, or you accumulated a charge and used the amp as a path to ground.

Does it have a three prong plug? If so, use a DMM to measure the resistance between the case (find an un-painted spot directly on metal) and that third prong. Resistance should be very low if they have a well designed, grounded enclosure.

If the resistance is negligible, what probably happened is that your body was charged and your amp acted as a return path. If that's the case everything should be fine. I was once working on a motor amplifier with a grounded case and I was working around some live 100VDC wires (I didn't know they had been turned on). One of the wires came close to the amp and zapped it, leaving a big charred mark on the front, but nothing inside was hurt because the case was grounded.

If the resistance is high, the case isn't well grounded and it might be possible that something was damaged.