Shock from speaker cable.

[Smokebreak3]

Troubleshooting a BF Showman that apparently cut out on a gig. Turning it off/on returned full volume.
I was troubleshooting the speaker cable that was being used, and had it plugged into the speaker jack of the amp on one end, and the other into my female to male speaker cable extension, then that into my shop speaker.
I was wiggling everything around looking for shorts, and accidentally unplugged the non-amp end of the questionable cable from the female end of my extension cable. I reached down to pick it up with one hand, and my other hand was still holding the end of the cable coming out of the amp.
I'm not exactly sure what I was touching, but I got a nasty shock . I'm not even sure I've heard of this happening.
What exactly happened?
This would be the same, essentially, as holding the speaker terminals with one hand, and the speaker cable coming out of a live amp. I just had the extension in there, to clarify.

[xtian]

Check that the Showman is properly earthed. You could even measure AC from tip and sleeve of speaker output to earth.

[pdf64]

With an open circuit secondary, the amp could've flipped into oscillation, putting out quite a high voltage eg 50V, which you would know about if you completed the circuit somehow.

I recall 100W Marshalls having an electrocution hazard symbol above the speaker sockets. I suppose if set to 16ohms, their output voltage would be twice that of a (4ohm) Showman.

[Smokebreak3]

This is exactly what happened , I believe. One more thing to look out for y'all.
This was a total fluke , and a nasty shock that went in one arm and out the other. I'm fine , and have been shocked a handful of times, but I'm going to the doctor tomorrow to make sure