I have a SERIOUS appreciation for high voltage now

[Amphiprion]

This is aimed at those among you who have not worked with high voltage, but are thinking about projects like tube amps and such. ALWAYS HAVE SOMEONE WHO KNOWS WHAT THEY ARE DOING WATCH OVER YOU. Never ever start out on this alone. I'd heard this from others before on another DIY site but never had an appreciation for just how strange and dangerous HV can be.

I was playing with a 5VDC->1kV RMS inverter today. It wasn't working, probing it showed a protection diode had gone bad. I replaced it, and was about to measure the output voltage from the inverter. I had it connected to a 100Mohm /1Mohm voltage divider so I could measure a nice and easy 10V without putting the meter close to its 1kV limit. I grabbed the nearest meter, which just so happened to have very skinny lead wires. And I probed the 10V across the 1Mohm resistor.

Or so I thought.

Instantaneously a spark jumped about an inch through the air up my finger through the probe lead wire itself. I don't know if it started at the tip and proceeded to go through the insulation, or just went straight through the insulation. Either way, I was getting zapped by sparks coming from rubber. I had measured the voltage across the resistor with 99% of the 1kV voltage across it, not the one with 10V across it. A faint stench of burnt skin rose to my nostrils.

Thankfully, the inverter was only rated at 5ma of output. I don't know where I would be had this been a tube amp.After this I don't think I'll ever contemplate a tube project without supervision or a lot more experience. Very scary stuff. Oh, and don't let the new guy on his 3rd day of work screw around with 1kV inverters

[Paul H]

Good advice Mark - and good that you're not burnt too bad!

[knifeinthesink]

yikes, scary.

Im glad you posted that. Its very easy to underestimate the danger in high voltage projects despite the warnings.

Ill be thinking twice before tackling anything more zappy then a gainclone.

[Armand]

I've repaired/modified tube guitar amps. Please be careful! I know of people that have gone into cardiac arrest. Always keep one hand in your pocket when you probe.

[tokyofist]

Always keep one hand in your pocket when you probe.

x2. Better yet, have multiple dmms with alligator clips so all you have to do is turn on the power and take your readings.

diyaudio has several stickied threads in the tube section that should be mandatory reading for those contemplating a first project

[chasw98]

I was introduced to high voltage when I stuck my hand in the back of a Janszen electrostatic cabinet many, many years ago. I ended up 6 feet backwards on the ground wondering where I was. I have been very respectful ever since.

[Arneson]

Mt latest zap experience was the digital camera repair I was just working on.
I removed the covers from three cameras to swap parts. The doner camera had a jammed lense, camera 1 needed an LCD, camera 2 needed the main board.
Once I opened them all up I was badly shocked and burned by the flash circuit.
It hurts, and you drop the camera.
So I have three burned fingers but two good cameras.

[Bent]

Always keep one hand in your pocket when you probe.

excellent advice - it keeps the second point of contact from being a direct path thru your heart.