Ladies and Gents,
When working on the outboard plate supply to my
linear amplifier my hand accidently brushed the Positive
HV stud on the beehive feedthrough and I became slightly
airborne for a second or two.
Even though the primary a.c. line was physically disconnected
from the 240 volt outlet, and even though I waited a good one-half
hour for the filter caps to discharge, the defective bleeder resistor
prevented the voltage from declining.
This accident was my fault alone because I failed to do the one
simple thing before going near a potentially dangerous area:
I failed to VERIFY the presence or absence of voltage on a
contact I believed to be harmless.
If the powerplant had been fully operational and not just energized
on the step-start circuit, there would have been 4,000 VDC on
50uF,5KV capacitance going through my hand instead of the 697 VDC
as later measured on the beehives.
The lesson to depart from this stupid move is to not trust anything
when dealing with the plate supply. Verify everything with a meter
and perhaps even use a shorting stick: Bleeder resistors, even ones
far over-engineered, do indeed fail, and I thank my Creator for this
opportunity to tell the story.
Respectfully,
Hal Mandel
KA1XO
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