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Old 09-11-2006, 11:37 PM
ARC Tech-109
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Quote:
Originally Posted by electronjohn
The worst broadcast-related zapping I know of concerns a guy working on a 20KW Collins FM. We're talking about 7800V or so @ about 3.3 amps in the PA supply. Guy got super pissed trying to find the problem...flung a crescent wrench into the transmitter's guts, only to have it land RIGHT across the terminals of a BIG filter cap.
Blew the wrench right back out, hit him in the face...broke his jaw and took out over a dozen teeth.
Hey John was that one of the Rev-105 transmitters by chance?

One of my worst experiences non TV related was when I was doing infared electrical inspections, this involved looking at electrical gear with a FLIR infared camera in areas including substations. I was at an oil pipeline pumping station in northern Michigan that uses 6000 horsepower 4.16KV motors to run at 3600 RPM, 3 motors run at a time. Incoming primary was 230Kv stepped down to 4160 then through vacuum contactors for the motors. Well the day I was there we were checking all of the motor contactor sets and pump west-2 was called into action the entire building went dim just before the fuses on the primary side popped, loud as a shotgun! One of the techs went out to replace the fuses and we were back in buisness while another tech was getting ready to isolate the failed contact bulb in the control, I understand it was a common occurance for this and they had a good stock of these fuses. It was caused by a phase loss. Well the other tech was a rookie and had no idea or real concept of what he was about to do. I was at the front of the cabinets taking current readings and as I finished went back behind to see what the guy was doing.
Without any protection at all and in his hand was a Simpson-260 meter, I remember yelling STOP! DONT DO IT THATS FOUR-SIXTEEN! but too late he stabbed the incoming 4.16 with that meter and blew himself out the exit door and into the yard. I went flying into the wall and my head crushed the door on the First-Aid station. My IR camera went flying through a computer monitor but still worked, the monitor was still on and I was getting a constant zap through my battery belt from the anode HV making its way down the camera power cable. The rookie sadly didn't make it and the other guy suffered hearing loss from the blast. I had earplugs having come from the pumphouse but even then it was extremly loud to me.
I stayed on the job for another 4 years and focused on substations, even had my hat snatched from my head as a result of 768Kv static buildup, never did get my hat back!
4160 might sound like peanuts compared to 27.5Kv on a 25" CRT but put a few hundred or even thousand amps behind it and life seems to short to mess around! These motors are breakered at 500 amps/leg with a time delay for starting, the incoming transformers are fused at 25 amps and the fuses are 48" in length.
Its like walking into a yard full of cobras, one will get you sooner or later.

109
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