Oops typo, I was hit with 3400 VDC
KRS
----- Original Message -----
From: G SEVEN <superiorwavelength@prodigy.net>
To: <W8JI@contesting.com>; <amps@contesting.com>
Sent: Thursday, April 05, 2001 10:45 AM
Subject: Re: [AMPS] Re: close calls
>
> My short HV encounter began when I went to disconnect the HV cable from
the
> RF deck when everything was supposed to be off. What happened is the relay
> that turns the HV on and off was stuck close and the bleeders didn't do
> there job as well, so when I when to disconnect it I was met by 2400 VDC
> that discharged from the capacitor bank into my arm. Wow, enough to get my
> respect. Now I am on the verge of paranoid, I get sweaty hand just working
> around this stuff. Now when ever I build a amp all the switches are non
> conductive and all the shaft for the input tune, tune, load knobs have
> insulated rods instead of aluminum. When its powered up and I have to work
> the controls I dont want anything to be conductive anywhere near my
> fingertips.
>
> KRS
>
> ----- Original Message -----
> From: Tom Rauch <w8ji@contesting.com>
> To: <amps@contesting.com>
> Sent: Thursday, April 05, 2001 6:42 AM
> Subject: [AMPS] Re: close calls
>
>
> >
> > > A good friend and famous multi-multi contest station owner, Phil
> > > Ashcraft, was killed while adjusting the tuned input on his 4X1 amp.
> > > All HV is lethal, but when you get past 5kv, one little mistake will
> > > probably be your last. The HV contacted his watch band, and "welded"
> > > his arm to the B+.
> > >
> > > Things that would never break down at 4kv such a components,
> > > insulation, and even arcs in open air are not unusual. Take all the
> > > precautions you can, especially when the covers are off. Amp builders
> > > are a dying breed...lets hope we will all go SK by natural causes.
> >
> >
> > I was almost killed by using the resonant choke circuit in Bill Orr's
> > handbook.
> >
> > I used the formula he suggested and build a resonant choke filter,
> > not knowing you really must have resonance above the ripple
> > frequency.
> >
> > The supply was a small 5kva pole pig with a bridge, driving a choke
> > input filter..for a pair of 3-400's. I used big oil filled caps that had
> > very high voltage ratings, they were from the utility company.
> >
> > When I powered the thing up, the 3-400Z's would arc from their
> > anodes to the grid support. When I disconnected the anodes of the
> > tubes, the blocking capacitor exploded on power up. When I
> > disconnected it, the bypass capacitor exploded.
> >
> > I placed a 5kV meter IN the ps cabinet, and attached it through a
> > HV insulated test lead (40kv rated) to the HV supply positive rail.
> >
> > I stood back (on a rubber HV blanket), kept one hand behind me,
> > and flipped a panel mounted toggle switch on. There was a flash
> > and the HV lead blew in two. It snaked OUT of the cabinet and
> > landed on my wrist (about two feet from the leads original position)
> > on the hand that was holding the grounded toggle switch. The only
> > thing that shut it off was the main fuses eventually opened.
> >
> > It burned a charred half-dollar sized hole in my wrist, and caused
> > second degree burns up to my elbow. I still have the imprint of the
> > toggle switch between my thumb and index finger!
> >
> > So what crossed my mind? I thought "Shit, how long will my brain
> > work now that my heart is stopped?" So I watched the clock on the
> > wall. When I saw the second hand make two complete sweeps
> > around the dial, I thought "darned, it didn't kill me".
> >
> > If I was not working on a rubber HV mat, and did not have the habit
> > of working with one hand...I'd have been toast.
> >
> > BTW I wrote Bill Orr a nice letter about this, and suggested he
> > might warn people about it in the area where his handbook
> > suggests using resonant filters. I have no idea if he ever changed
> > his book.
> > 73, Tom W8JI
> > W8JI@contesting.com
> >
> > --
> > FAQ on WWW: http://www.contesting.com/FAQ/amps
> > Submissions: amps@contesting.com
> > Administrative requests: amps-REQUEST@contesting.com
> > Problems: owner-amps@contesting.com
> >
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
>
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|