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Re: Terrified Parents
Original poster: Ed Phillips <evp-at-pacbell-dot-net>
Tesla list wrote:
>
> Original poster: dhmccauley-at-spacecatlighting-dot-com
>
> Definitely an urban legend. HV probes always have dividers built in them.
> Thats the whole purpose of a HV probe. If it didn't have the divider, it
> would basically be
> just a metal rod with an insulated handle.
>
> However, i do have a story that is true. A technician at my company was
> working with a radar transmitter in the high voltage cabinet, and was taking
> oscilloscope measurements from a
> modulating high voltage deck. The deck itself is low voltage (28VDC with
> +/-1000VDC for the grid modulating system), but the entire deck is floated
> at the cathode voltage of the TWTs
> which is about 45-60kV depending on TWT. Anyways, the oscilloscope was
> being floated on top of the deck to measure something in the deck, and the
> technician went to change a setting
> on the scope and . . . well . . . you can imagine what happened next.
>
> Dan
Sounds remarkably like an event I was involved in at Hughes Aircraft,
about 1971. We had a high-power Ku Band TWT operating at a cathode
voltage of -65 kV and wanted to look at the grid modulation voltage.
One of the guys found someone who would rent us a battery-operated scope
with enough frequency response. Stuff was set up and the scope was hung
from the ceiling with lacing cord. The transmitter breadboard was
operated in a big tank of oil about 3' square by 6' long and scope was a
couple of inches above the oil. The thing worked pretty well but one
day someone managed to arc the case of the scope to ground! It made
quite a bang. The interesting part is that the scope still worked and
was returned to the renting agency with no mention of what had happened
and no subsequent complaints from them.
I often think about this when guys are trying to figure out how to
monitor what's going on at the HV terminal. Maybe someone could rig a
transparent (wire screen?) toroidal terminal big enough to hold the
scope and then watch the scope trace through the openings.
Ed