[Amps] SAFETY WITH HIGH VOLTAGE

[Dale J.]

I learned at about age 15 on a homemade intercom to never trust 
bleeders.   All shops dealing with Hv should have a chicken stick.

I am happy to see you are still with us.

Dale, K9VUJ


On Aug 20, 2004, at 17:25, Harold B. Mandel wrote:

> 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
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>