[Milsurplus] [MMRCG] A WARNING: The Death Angel Flies Close.

[Ray Fantini]

Sorry to hear about your accident but don’t be too hard on yourself. Everyone makes mistakes. Some worse than others. The original design of the transmitter only applied high voltage when the transmitter was keyed. I used the original keying relay (K301) and keying system using the old side tone contacts on K301 to control the AC input to the plate and B+ supply thru relays so the only time HV or B+ was applied was when the transmitter was keyed. Also had the control line that ran from the old side tone relay contact on K301 tied to the power level control switch on the power supply deck so when in the TUNE mode it held open the control from the HV supply but still allowed the B+ to be applied to the oscillator, IA and PA screen. This allows you to set the oscillator on frequency and tune the IA stage and get that all set before applying plate to the PA.
It’s a crazy design but somehow the transmitter has no issues having full screen voltage applied to the PA without plate but that was the original design for that transmitter and it don’t appear to do the PA tube any harm.
This kept the interlock switch as an additional safety on the power supply deck but a real problem is that the side screens of the transmitter case are not interlocked. 
I always try to keep high voltage and B+ away from all the tank circuits unless they are transmitting and avoid any scenario where HV is applied to the tank without any drive.
Transmitters as small as an ARC-5 or TCS can have 400 volts or more on the output tank and that’s bad enough and when you get into larger transmitters like the ART-13 or something as big as a BC-610 the high voltages are easily lethal. The TBW and GO transmitters fall into that category.
A lot of good suggestions have come up and we all need to take care but a couple things for those of us running the big iron to remember are first: Never defeat or bypass the interlocks! And second is even when you may be prototyping and not ready to do a finished install still try to keep things like HV removed to all stages until necessary, don’t matter if the tube is biased off or whatever. If you are not transmitting you don’t need the HV applied.

Ray F/KA3EKH

-----Original Message-----
From: MMRCG at groups.io <MMRCG at groups.io> On Behalf Of David Stinson via Groups.Io
Sent: Saturday, November 16, 2019 2:35 PM
To: milsurplus at mailman <milsurplus at mailman.qth.net>; ARC-5 <arc5 at mailman.qth.net>; Boatanchors at mailman <boatanchors at mailman.qth.net>
Subject: [MMRCG] A WARNING: The Death Angel Flies Close.

A WARNING:  Close Encounter with the Death Angel.

Some of you may remember an article I wrote some years ago, "Shockless," 
which was published in an Australian ham publication.  The point was how our focus and attention decline as we age and the great danger of working with High Voltage where a momentary mental lapse or getting out-of-order in our safety procedures can have tragic consequences. The article presented alternatives, like much-lowered B+ voltages, which can bring our old boatanchors alive without excess danger.  Well, I've just had The Death Angel pass so close I could feel his cold, fetid breath and the icy wind from his black wings.  It's only the grace and goodness of The Lord that I am here to write you this warning.

As most of you know, I'm working on a WWII Navy GO-9 transmitter and the project is nearing completion.  The power supply for this transmitter produces 1400V and 540V under load.  When unkeyed, the B+ is near 1800V.   This level of voltage, if contacted across the body, is almost always instantly fatal.   I've been very careful to go slow, remember safety, have a sequence for power-up and power down.  Checks and rechecks before putting a hand in there. And it worked.  Until a moment of inattention and a neglected safety check, when it didn't.

I've had the High Voltage fed from a separate AC primary through a variac while tuning and testing.  When plugged directly into house current, the Low B+ is too hot (800V), so I was working on toning it down.  Got that all sorted out, so power down to make a couple of changes.  Turn off the variac.   Turn off the Filament supply. Wait for the resistors to bleed-away the charge, (**but neglected to check the Hi 
B+ voltage test point**).  The "B+ ON" warning light was facing away
from me.
Just one thing my old, distracted brain forgot:  The Hi B+ wasn't plugged into the variac- my soldering iron was.  The Hi B+ was plugged into the house current, fully live, sitting at 1800 V like a coiled rattle snake.  "Looks like one of the B+ feed wires is a little too close to ground.  I"ll just move..."

WARNING:GRAPHIC PHOTOS
https://photos.app.goo.gl/9NLRVGj93NpSBgdB6
https://photos.app.goo.gl/C4KycfbxKhTYLLre9

Flash and bang.  If my other hand had been on anything conductive, of if I were on a concrete floor instead of a wooden deck, I would not me writing this.  I would have been instantly killed.  Worse, I would have left an deadly rattle snake, coiled to bite the family member who found me.   The burns on my left hand  look superficial, but my hands won't stop shaking.  The pain is pretty intense.  There is likely some nerve and deep-tissue damage; that will be evident over the next few days. The Lord God, in His mercy, decided to let me continue to draw breath, and I prayed my gratitude to Him for sparing me another day.
  But one does not get-away with such stupidity unless one is in Congress, and I ain't.

I am going to finish this project; it's too close now to give up on it. But DIrty Harry's advice echos in my empty head:
   "A man has got to know his limitations."
Have had close calls before, but nothing nearly so deadly as this.  Such Voltages are "a young man's game."  I think I've just had my last warning.  I simply no longer have the mental sharpness essential to deal with such danger.   I will never again take-on any project that requires such voltages.  I dearly love reviving these historic and beautiful rigs, but not enough to die for them.  All my pending projects that require this sort of voltage are going away.  All my iron at this level will be given away.
 From now on, I'm a "little rig" sorta guy.  Got no more room for big rigs anyway.

Be smarter than me (not very hard).  Be safer than me.  Don't do this.
And thank The Almighty for every new day.  You never know when it will suddenly end.

GL OM ES 73 DE Dave AB5S



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