Got shocked BAD

[jcat5503]

Yesterday during rehearsal I got the hell shocked out of me!

I was playing on my half powered Rocket I recently built and I was plugged straight in and I decided to put a pedal in front of it so I grabbed my Timmy OD and plugged it all in (only pedal) and hooked the one spot up and started playing without it on and then I bent down to switch it on with my finger and BOOM lit me up! I threw my guitar and everything. I've got a burn on my thumb from it

I've been hit by 110 several times and this was WAY worse. I was disoriented for about 5 seconds

Anyone know why in the world this could have happened??

[Structo]

I have no idea what went wrong but do not play that amp until you get it sorted out!

You have a hot chassis or something, open that amp up asap and fix it!

Sounds like the B+ is on the chassis.

Folks this is why we stress safety and proper grounding and fusing of all tube amps.

Glad your obituary was not in the paper the next day.

[M Fowler]

Jason,

Glad your okay and Tom is right you have a hot chassis and need to track that down before that amp is ever used again.

Mark

[jjman]

The One Spot is not directly referenced to the wall's ground but could somehow short the wall ac thru, I guess. The pedal's body and switches are likely "grounded" via the ground leg of the guitar cables.

Check the amp of course. That's were the really high and DC voltages are. If you remember the zap you may remember if it had that "vibrating" feeling to it that comes from ac.

And the 117v wiring in the space should be verified:

[img:576:411]http://www.oldhouseonline.com/wp-conten ... tester.jpg[/img]

[jcat5503]

I am always very careful when working with amps. But this came out of no where!

I'll check when I work the courage up. I'm a little gunshy now!

My assumption was that the B+ is running through the chassis as well and when I went to turn the pedal on I completed the circuit

350 volts doesn't feel good at all!

Everyone please be careful!!

I wonder where to start when trying to hunt this down. This is a new one to me

Anyone else experienced this?

[jcat5503]

The One Spot is not directly referenced to the wall's ground but could somehow short the wall ac thru, I guess. The pedal's body and switches are likely "grounded" via the ground leg of the guitar cables.

Check the amp of course. That's were the really high and DC voltages are. If you remember the zap you may remember if it had that "vibrating" feeling to it that comes from ac.

And the 117v wiring in the space should be verified:

[img:576:411]http://www.oldhouseonline.com/wp-conten ... tester.jpg[/img]

I own this exact thing, I'll check it and see. Never had a problem with it though, but who knows!

I'm not sure what kind of shock it was. Didn't feel anything like getting shocked by 110!

I'm thinking it was DC off the B+

[Noval_novice]

That's scary! Yeah, I would definitely check the mains ground and the power rail.

[tubeswell]

I've been shocked a couple of times, once as a kid - by faulty xmas tree lights, and once while voltage testing one of my amps (and it was as a result of my own stupidity). I wouldn't ever want to do that again. Check that your chassis earth is properly and securely bolted on with a locknut (and for that matter make sure that all the nuts and bolts in the amp are tight). Then go thru your amp with an R-meter and check that the B+ supply side isn't shorting to the ground return side. And check all your wiring joints, solder-points, socket pins etc to make sure that nothing isn't shorting to ground that shouldn't be (because something probably is shorting that shouldn't be would be my guess). And take that FX pedal to a tech.

And go to the doc and get your ticker checked out

[jcat5503]

I've been shocked a couple of times, once as a kid - by faulty xmas tree lights, and once while voltage testing one of my amps (and it was as a result of my own stupidity). I wouldn't ever want to do that again. Check that your chassis earth is properly and securely bolted on with a locknut (and for that matter make sure that all the nuts and bolts in the amp are tight). Then go thru your amp with an R-meter and check that the B+ supply side isn't shorting to the ground return side. And check all your wiring joints, solder-points, socket pins etc to make sure that nothing isn't shorting to ground that shouldn't be (because something probably is shorting that shouldn't be would be my guess). And take that FX pedal to a tech.

And go to the doc and get your ticker checked out

Yeah this seems like the way to go. I'll do it in a few days, like I said I'm pretty gun shy at the moment about the amp. Theres a million things it can be.

I am going to recreate the situation and use a meter, instead of my body! This way I will maybe see something


Man I hope theres nothing wrong with my heart, I'm only 21 years old!

[SteveG]

Theres a million things it can be.

Well, not quite! It should be relatively easy to diagnose the problem. I'd take the advise in the above post and check with a multimeter and also visually before you plug the amplifier in again. The question is, if the B+ shorted to the chassis, why didn't a fuse blow?

If your heart is still beating, I think you can assume you got away with it.

Steve

[JamesHealey]

was it like being hit by a truck in the chest or was it more like some bastard throttling you and not letting go?

that's the only way I can describe DC vs AC.

Neither are pleasant but the scariest shock I ever had was a DC, even though apparently AC is more likely to kill you.

[overtone]

An experienced Radio Ham told me that you should get yourself checked through at the hospital after a DC shock because you can still get problems 24 hours later.
Has anyone else heard that too?

[NickC]

Greetings jcat5503

I'm glad to hear you're okay, despite getting badly shocked. I took a hit from an undocumented 480V AC line in a factory many years ago (power was supposed be off for the entire wing ... it wasn't). The screw-driver I was holding took most of it. The blade end vaporized. I got thrown about 5 feet into a cinder block wall, which was lucky.

I was working on an amp build a little earlier today and had this thread fresh in mind. I secured the ground meter probe with a clip to chassis ground, had my left hand in a back pocket, and carefully took measurements with the other probe in right hand.

After that I went to check some specs online and after awhile realized I was typing with just one hand, the left one in my pocket ..... I had to laugh at myself when I realized why. Once bitten, twice shy!

Be Well,
Nick

[xtian]

I have a friend who lost the use of an arm in a bicycle accident. He has a job already--doctor--but maybe amp technician can be his fallback profession.

It's good to laugh after escaping grave injury!

[boots]

I took 600 VAC in one arm & out the other when I was about 20, and it knocked me backwards and scared me silly, but I was lucky (measuring voltages on a transformer out of an old TV). Don't know if I would get away with that now at age 50! I would say getting hit in the chest by a semi truck is a pretty accurate description.

I recently got bit by about 400 VDC across a couple fingers, with no ill effects other than an uncontrollable stream of obsenities. Always keep one hand in your pocket when tinkering! Taking a shock thru the torso is MUCH more serious that getting your fingers bit.

You should be able to do a lot of your troubleshooting with a schematic and ohm meter with the power off. It's also possible there was a fault with the building, if you were playing a gig in a a different place than usual.