I know there are a lot of you out there that have tube type amps and some of those have really high voltages in them. Some are a couple of thousand volts.Those of you that dare to work on them should pay special attention to your meter leads of your VOM.I worked in the broadcast biz for 22 years and routinely worked with voltages as high as 5000 volts with never an incident. I attribute that to training and respect of what high voltage can do. I never feared working on high voltage power supplies but I was always cautious and aware of what I was doing as I respected what lurked in those power supplies.Failure to respect high voltage can be disastrous to your health.
Yesterday I was cleaning up a few things in the basement and found some old transformers I had forgotten about. I set them up on a towel on the wooden kitchen table which was on the hardwood floor and I sat in a wooden chair and connected my variac to see just what the voltage was. A couple were high current filament transformers and a couple were low voltage power transformers but one was obviously a plate transformer from a transmitter.It was meant to be run from the 240 v AC line but I had it connected through my variac to the 120 v line and figured I would just multiply the output voltage by two to determine the true output value of it. It did have a plate on it detailing the specs but it was unreadable.I was told it came from a Collins transmitter from many years ago. The meter I use is a Triplett model 630-PLK,an oldie but a goodie.It has an AC and a DC range of 5000 volts.All was going well until I tested the HV transformer. I had one lead connected to one side of the secondary and had the other lead in my left hand and held it against the other terminal of the secondary. (mistake #1) With my right hand, I turned up the voltage with the variac. ( given mistake #1 this was mistake #2) As the voltage approached 3400 volts AC I began to feel a slight tingle in my left hand. I thought nothing of it as I have some circulation issues when I hold my hand/arm in a certain position for very long and it felt the same way. (mistake #3) Seeing 3400 volts on the meter when the variac was full on I decided to turn the voltage down before removing the meter leads because sometimes there can be an arc from the lead to the terminal with that kind of voltage.Not taking my eyes off the meter lead in my hand I reached with my right hand for the variac knob when things went bad.I touched the metal case of the variac and instantly it felt as if my skin was on fire and someone stabbed me in the chest.I barely remember yelling or grunting something as I was thrown to the floor.I ached all over and it was hard to breathe. My wife came running in a panic thinking for sure I was dead or on my way to being so.I thought the same thing. Being a registered nurse she quickly checked my pulse and it was as fast as a hummingbird but strong and regular. After a minute or so I sat up and began to wonder WTH happened. After she realized I was going to be OK my wife ripped a strip off me. I told her she just did'nt want to have to put her lips on mine to give me CPR. ( mistake # 4) After regaining my wits I checked things out. In my haste to do something I overlooked what leads I had used. I could not find my regular meter leads that are made from 5,000 volt high voltage wire and instead had picked up a set that were from a differant meter. Printed on the test leads was "600 volts".With nearly six times the max voltage applied to the test leads the insulation broke down and leakage currents were present on the meter leads. That was what was causing the tingling sensation in my hand and since I was insulated by the wooden furniture on the wooden floor that was all I felt. As soon as I touched the metal cased variac I was grounded.
My muscles still ache especially the one in my right shoulder and neck and I have a headache but all is well. I still do not fear high voltage but I could kick myself for not paying attention to what I was using for meter leads.Yesterday was a close call,one I do not care to repeat. If any of you are working with high voltage pay attention to the voltage rating of the meter leads.It may be the only thing between you and the after life.
Yesterday I was cleaning up a few things in the basement and found some old transformers I had forgotten about. I set them up on a towel on the wooden kitchen table which was on the hardwood floor and I sat in a wooden chair and connected my variac to see just what the voltage was. A couple were high current filament transformers and a couple were low voltage power transformers but one was obviously a plate transformer from a transmitter.It was meant to be run from the 240 v AC line but I had it connected through my variac to the 120 v line and figured I would just multiply the output voltage by two to determine the true output value of it. It did have a plate on it detailing the specs but it was unreadable.I was told it came from a Collins transmitter from many years ago. The meter I use is a Triplett model 630-PLK,an oldie but a goodie.It has an AC and a DC range of 5000 volts.All was going well until I tested the HV transformer. I had one lead connected to one side of the secondary and had the other lead in my left hand and held it against the other terminal of the secondary. (mistake #1) With my right hand, I turned up the voltage with the variac. ( given mistake #1 this was mistake #2) As the voltage approached 3400 volts AC I began to feel a slight tingle in my left hand. I thought nothing of it as I have some circulation issues when I hold my hand/arm in a certain position for very long and it felt the same way. (mistake #3) Seeing 3400 volts on the meter when the variac was full on I decided to turn the voltage down before removing the meter leads because sometimes there can be an arc from the lead to the terminal with that kind of voltage.Not taking my eyes off the meter lead in my hand I reached with my right hand for the variac knob when things went bad.I touched the metal case of the variac and instantly it felt as if my skin was on fire and someone stabbed me in the chest.I barely remember yelling or grunting something as I was thrown to the floor.I ached all over and it was hard to breathe. My wife came running in a panic thinking for sure I was dead or on my way to being so.I thought the same thing. Being a registered nurse she quickly checked my pulse and it was as fast as a hummingbird but strong and regular. After a minute or so I sat up and began to wonder WTH happened. After she realized I was going to be OK my wife ripped a strip off me. I told her she just did'nt want to have to put her lips on mine to give me CPR. ( mistake # 4) After regaining my wits I checked things out. In my haste to do something I overlooked what leads I had used. I could not find my regular meter leads that are made from 5,000 volt high voltage wire and instead had picked up a set that were from a differant meter. Printed on the test leads was "600 volts".With nearly six times the max voltage applied to the test leads the insulation broke down and leakage currents were present on the meter leads. That was what was causing the tingling sensation in my hand and since I was insulated by the wooden furniture on the wooden floor that was all I felt. As soon as I touched the metal cased variac I was grounded.
My muscles still ache especially the one in my right shoulder and neck and I have a headache but all is well. I still do not fear high voltage but I could kick myself for not paying attention to what I was using for meter leads.Yesterday was a close call,one I do not care to repeat. If any of you are working with high voltage pay attention to the voltage rating of the meter leads.It may be the only thing between you and the after life.
