Amp bite

[pkb]

This is what an amp bite looks like.

I think it was from the 16uf 475v cap supplying the phase inverter tube (high 300's for voltage).

I was 'in the zone' and attempting to adjust the plate voltage of a particular tube by removing another tube from a different channel of a Fender Deluxe Reverb. I didn't have my capacitor cover on since I was working on the power supply already. I thought I'd unplugged the amp but I'd only turned it off. As I was fumbling around to find the right tube (by feel--I was too 'in the zone' to turn the chassis over and look at what I was doing), my palm touched a positive lead on one of the caps.

The shock was amazing. I would have called the focus I had before shock 'very high'. The experience of having a few hundred volts loose in me changed that focus to what I'd actually call 'extreme'.

I'm happy to have survived the lesson. I still haven't figured out the preamp voltages yet.

The following is what an amp bite looks like: the small white mark shaped like a film resistor body is where the electricity entered.

If this short post helps anyone remember to check that their amp is unplugged at least once, I'm very happy.

Patrick

[xtian]

Hoo boy. This is like those new, ugly photos on cigarette cartons--not going to make us stop, but makes you more careful. (I don't know how someone could be more careful about smoking...)

[labb]

and don't forget to discharge the caps. You are lucky you did not get across the 120 AC at the fuse.

[Structo]

Bad!

What was your other hand touching?

[pkb]

Bad!

What was your other hand touching?

You don't wanna know.... =)

I think I was holding my chopstick.

I don't really remember, but I do remember thinking "I'm glad I wasn't holding onto the chassis."

[Gaz]

I've only gotten visible bite from hitting the fuse holder. (keep saying I'm gonna start heat-shrinking those.) I've also had the pleasure of getting a lesser voltage through the chest while trying to be cool guy and jumping caps in and out while playing. Of course I always forget to stop holding the chord!

[Bob-I]

Yea, they can nip for sure. I have a black spot on my hand in just about the same place from a zap about 5 years ago.

[tubeswell]

Get yourself onto an insulated floor. The thing went through you somehow. I'm guessing it got through out through the floor.

[Gibsonman63]

Tubeswell, your tag line takes on a whole new meaning in this thread!

Home Depot/Lowes has those rubber tiles that fit together like a puzzle for about $15 per package of 4. Plus, they cushion your feet. Hmmm... I tend to be barefoot all the time when I am home (and a lot of my gigs). Maybe I need to rethink that when I am working on amps.

[amplifiednation]

Was that bite from the amp bug?

[pkb]

Was that bite from the amp bug?

It probably was. Glad it wasn't a bandsaw bug!

[Structo]

You do understand if you get a shock like that and it goes in one hand and out the other, that your heart is in the middle?

Good way to stop the old ticker.

Never have two hands in the amp.

Good practice is to stick one hand in your pocket while probing, if the amp is on.

Also, always double check for voltage at the filter caps when working on a unfamiliar amp that is unplugged.
Many amps don't bleed down the voltage when turned off so there can be a charge left in the filter caps, even unplugged, even a day later. (or longer)

[amplifiednation]

I was putting suede on an ODS cabinet last night and decided to take my shoes off and kick it on the back porch while the last piece of suede dried. About 2 minutes later I dropped my tolex blade (blade down!!) on the top of my foot. It was cripplingly painful. I will spare you guys the photos. I can barely walk today.