The AM Forum

Lucky to be here to write this today.

Yesterday I got hit with 6kv.  Through my hand, out my leg.  Also a small hole in my opposite pinky finger. 

Hand hurt so bad it was on fire for a couple few hours, until the morphine kicked in.

Bought me an overnight stay in the hospital thus far.  Hand hurts still, burns being attended to.

Never trusted the Millen hv connector.......  This amp was complete, bought from someone else.  Was reaching around to move the wire from the line section to the bird.  Plasma arc reached out and hit me three times.

Merry Christmas everyone.  This one will have a very special time for myself and my family.

Be careful friends, fellow hams and homebrewers.  I got hit, all covers on, safety interconnects installed and working and all the screws in this thing.

--Shane
KD6VXI
(from the hospital bed, 17 hours after the fact)

Edited for pics

Pic

Pic

Have a pic of the exit hole in my leg, but it's too big to post.

Its good to hear that your ok!
Ive never been bit with that much, 4400 was the highest for me.. Changed my mood that day.
I certainly hope that wasnt the power supply that you built from the parts you bought from me.. We both know what currents its capable of!

Take care   73's


Sam

No, not with the xformer I got from you, but this was no joke, either.  2.5A ccs at 4200 vac.  16x1800uF caps.

Someone else built it.  Doesn't excuse anything but it sure feels better to be able to say that!


Worst thing is, this is one of those injuries 'you hear about'.  Amp was completely done, all screws in it, had been tested.  Was just 'moving a wire' into a more accessible area.

I got really lucky, I don't believe I had a direct strike.  I believe my hand was close enough to cause a plasma arc to start.  I //heard// 3 distinct strikes before I was able to throw my self free.

Just as easily could have been someone's pet, a grounded piece of coax, etc. That got too close to the connector / wire area.

Wake up call, and as you said....  A mood changer!

My nurse is a traveling nurse from Colorado.  Her boyfriend is a W1 lander.  She asked me what had happened, I explained it was from a 'ham radio amp', and she seriously turned white (she's Hispanic)...

Her boyfriend had sent her a pic that afternoon.....  He got the station up at their new house in Denver!   She responded with pics of my hands and my call! Lol.  Poor guy.


--Shane
KD6VXI

 :o

Um... Yes, Your defiantly lucky to still be here..  112.5 uf Is one hell of a supply to discharge through you and to still have the 2.5 amp grunt with probably a 5 amp peak behind that... Makes my chest hurt from here.. I know that you know your stuff but we all tend to get a little careless around HV.
I have several times found myself reaching into a "hot" hv supply, the few times Ive been bit, Im sure I will have some long term issues from it. You might want to revisit the doc after you heal.. An EKG might be a good thing to pursue just to make sure you dont have any lingering heart damage.
You have to hang out on this planet for years to come, there aren't enough competent techs that will touch the big boy stuff.. ;D

Happy to hear you came out well Shane, these are no voltages to be careless with. I always worked with voltages up to 12 kV DC up to 150 kW. It made me very careful. My "HV teacher" always told me to learn from an old technician, bad HV technicians don't grow old....
He told me to connect HV always with a coax and in addition a screwed-on ground wire. An isolation issue at the HV coax will always result in a short and the HV can't escape.

Glad you're here to report the incident Shane.  I never liked the Millen HV connector either.  I use HNs and a proprietary HV connector that has a long leakage path and no chance of exposed conductors to reach out and bite.
I'm curious what the doctors' concerns were after a 6 KV hit.  Were they primarily looking at cardiac electrical stuff?  Do you know if they ran a cardiac enzyme blood test?  (That one checks for cardiac muscle decay products in the blood stream.)  Any concern for immediate internal tissue damage at input and output sites?
Or did they just want to watch you grab a cold water pipe to make sure you were fully discharged?
 de Norm W1ITT

Wow, pretty nasty hit, Shane.

Fortunately it looks like mostly surface damage.  I'd say the path was spread out over a wider area, which is a good thing, rather than everything going into one small point and exiting at another, thru your heart, head or wherever.

Back in the sweaty summer of 1972, I got my first and worst belt.   800 VDC went from one hand to the other, right thru my chest. My right hand's flesh got torn open because I could not let go. It caused 3rd degree burns, charred flesh, no blood - cauterized. The skin on my index finger was torn open and hanging.  It took months to heal and kept getting infected. I really should have gone for stitches. I was afraid to go near that rig for 2 days.

So, obviously that 6KV accident you had could have easily been fatal if it took the wrong path.

When I look back at all the MANY, MANY risky, dangerous and stupid things I've done - and near-accidents I've had, I know there is a guardian angel watching out for me. You have one too...  There can be no other answer... :-)  

Hope you heal fast, OM.

BTW, I have NEVER trusted any type of slip-on, screw-on feedthrough HV plugs.  I make it real obvious and strong - I use a 2-3" tall ceramic pillar mounted on the chassis for all to see and avoid in the HV area.  A HV lead connected to a HV circuit on a pillar has never failed me.



T

Glad you walked away from it.  Extremely lucky.

2.5kV for me about 20 years ago.  The path was between the back of my hand and thumb on the same hand. The back of my hand was touching the chassis of a PS and my thumb brushed a hot terminal ever so slightly.  Suffered a similar injury to my thumb. A pin hole where the flame shot out. And a burn mark on the back of my hand. Amazing thing was I did not feel it through the rest of my body.  My heart rate did not change. Talk about luck... until a week later when I needed minor surgery on the thumb for a deep tissue infection from dead tissue.  

Glad you are ok. Well at least you can list a conductor on your resume! It definitely reaffirms the fact that we are not immortal.

Wow, very very very scary stuff.  :o

Wonder if you can say if you were touching the Millen connector itself?

Was the rig OFF?

Is there a bleeder on the HV?

If you were not touching the Millen connector, perhaps the insulation on the wire
broke down...

Not sure what the max voltage rating on the Millen connector is...

And, I never liked the Millen HV connector much, I rather think 6kv is probably at the hairy
edge of what it can handle...

Glad you are around to tell us all about it! Complete recovery!

                              _-_-

Thanks to everyone for the wishes.  It definitely served to WTF up (wake the ....).

I don't believe I got a 'direct' hit....  The 70A breaker in the power supply didn't trip nor did the panel breaker, an adjustable magnetic hydraulic set to 60A.  After I 'walked it off', I went out and shut the main panel to the shop down.  Feels like it will be a minute or two before I head back out.

My big dummy load has an HN connector.  I'll have to look into it for HV.  I've used rf style connectors for kilovolt stuff, but nothing over maybe 1.2kv.

I did get a small burn on my index finger on my rt hand somehow.  Almost like step voltage type burn, looks like a kernel of yellow corn right up against my nail.  I've no idea why, unless it was Corona? Lol.

Conductor....  Hahahaha.  I'll have to tell my boss that, although he told me find a new hobby last night.  As an electrician, he feels I'm around voltage too much already.

I think the worst effect is to my kids.  My oldest is pretty shook up.  Definately time to reassess a few things.


Bear, the rig was on, covers installed, etc.  I had already loaded it up, unkeyed and didn't like how a wire was 'dangling' around the back (from a line section to the bird meter).  I went to brush it out of the way, and 6kv jumped...  I think if I would have had my hand anywhere closer I'd be dead.  It did hit me a total of three times before I was able to throw myself free, so I can say the plasma path wasn't continuous.  I think the exit through my leg was probably the first strike. 

Scary thing was the damage to my rt hand.  It was in my back pocket.....  So I KNOW I had some voltage go thriugh my heart.

I was admitted through 'urgent care'.  My fiancee pretty much insisted I at least get checked out.  The doc upon hearing what happened spoke to hospital admitting (the urgent care was physically connected) and they said to admit me.  They hooked me up to a remote heart monitor for 24 hours, had an iv drop of saline (bag and a half).  They also did a full ekg when I was admitted, and chest x rays.  The nurse at urgent care has a W1 call boyfriend who sent her pics of his station he set up yesterday.  Her response was a pic of my hand and my call lol.

If I missed anyone's questions, feel free to poke me and say hey!  Lol.

Again, thanks everyone.  

--Shane
KD6VXI

Oh, Sam.  As to follow up care.  Yes, they wouldn't let me leave until THEY (hospital) set my follow up appt with my primary care.  Like you said, they also stated:  their is the possibility of something not seen today, or that manifests itself later.  The doc left work up to me.....  He said physically I appear OK but if I have any doubts, pain or anything else...  Don't.


Also.  Electric chair:  cruel and unusual punishment.  🤔🤔🤔. Shyte hurt!

--Shane
KD6VXI

Shane

Good, Definitely need at least one follow up check out, probably one 6 months from then also.

Electric chair.... Well, you forgot to wet the sponge....



73's


Sam

Shane,

Wow. Very scary.

2KV knocked me on right on my azz and I didn't feel quite right until the next day. I was in my 20's back then, wouldn't want to take that hit today.

You must have unfinished work to do in this world.

I can't recommend a good connector, but I think a shielded (and grounded) cable like RG-8 would be safer. See application note attached.

Stay safe,
Don

You said:

"I don't believe I got a 'direct' hit....  The 70A breaker in the power supply didn't trip nor did the panel breaker, an adjustable magnetic hydraulic set to 60A."


Shane,

BTW when applied to the right place on the body, it only takes about 18 mA  at 2KV to kill someone.  That's just 36 watts.  (or much LESS voltage - whatever it takes to draw 18 mA thru the critical body areas.)  Your 70A breaker at 240V = 16,800 watts.   The breaker didn't even know you were there... :-)    Those movies showing electrocutions with the lights dimming and transformers humming are a crock of bull hype...   IE, primary fusing and breakers will not protect anyone, even on a more sensitive, smaller 50 watt Novice tube rig.  Has anyone EVER seen a breaker or fuse blow when getting belted on a tube TV, tube audio amplifier, small ham TX or tube receiver, etc? ? I doubt it...   This is something to remember.

The only thing that usually saves anyone is that they were somehow able to get away and break the circuit.... period.  As the body cooks, the current will increase (and become even more deadly) as the flesh carbonizes and the path resistance goes down.   There is no small-signal fail-safe trip protection from HV to chassis ground, so we are screwed.



So glad you are safe, OM.

T

"  had an iv drop of saline (bag and a half).  "

So, I guess they figured that you were not conductive enough.


klc

Hahahaha!  Yeah, well.

A good friend of mine was a conductor for Union Pacific for years....  Guess we have something in common now?

--Shane
KD6VXI

Dude you rode the lightning What's up with that you trying to visit Golden Arms or Dragon Base. Don't forget the big man on reservation. I won't lecture you know better. That was just a little warning. I am glad you are above ground. I am sure they did an EKG. You know the thing that is scary if you had internal arcing. that happens in your chest. The bad thing is when tissue dies and they don't see it. Did you get that funky metallic taste out of your mouth yet.
47

Congratulations on surviving. Down to eight lives now. Maybe MOSFETs are in your future.

I'm glad you are 'OK' after that. When you feel like it, could you please post (pr0n) pics of the amp and PS, including the area of the Millen connector and Bird line?

My 3CX AM project is kinda stalled right now but I am still trying to be sure that any HV connectors are enclosed within the rack with doors shut, and opening the doors shuts off the HV. Now I can understand that the line section and any cables should not be close to the HV terminal if it could be avoided, I appreciate that. There are always some risky times when trying to get something to work and It might be worth it to hook up a strobe that flashes for me when the HV contactor is energized as well as an extra HV meter in the back of the thing as meters are cheap enough, boxes of them here. That project has the stock Henry RF generator HV connector right now.

The tabletop 3CX amp here is another matter. It has also a Millen HV connection exposed on the back, fed through HV wire surrounded by braid tube from RG8, with a ground lug. There are a couple inches of HV wire and the Millen connector exposed outside the enclosure and about 4500V there. I don't like that kind of hookup. I've never trusted HV connectors to be touched in any way let alone with HV enough to arc.

Someone on this message board once said that there is a big difference for arcing, corona, and problems from 'conductive dirt' when things get above about 3 or 4 KV.

I work by myself and am nervous about low B+ voltage ranges and possibly afraid of real plate voltage. Not sure it is fear but it is some kind of excitement feeling and always on my mind when the HV is being worked with to the point I check/look at the HV meter is at zero 2 or 3 times before grounding the HV with a hook and fiddling about.

Again very happy you only got a nasty shock. Merry Christmas! The gift of life!

Had a very close friend, years ago, WA2LSE. Bill was admitted to the hospital for an apparent heart attack. When he woke up he asked the doctor what happened. The doctor was reluctant at that moment to say how severe it was. Bill looked at the doc and said, I know you used the paddles on me - I know what it feels like to be knocked on my a** by electricity! I can only claim to getting bit by ~800V, inside a power supply for my friends ART-13. IT taught me RESPECT!

Yep, thankfully most of us learned that lesson very young. Perhaps starting with sticking our finger into an AC wall socket.  Though in your case, 800 VDC is no picnic if it hits you right.


Here's the goods:  Take a DC ohm meter and grab it in each hand. What do you read, 200K? Lots of dead skin there.      Now put it across your tongue… 10K? Moist, tender skin.     (That's what I just read measuring myself)

So the initial shock will depend much on what type of skin the current initially hits and if the layers underneath  have a lot of moisture or not. I can picture a 2KV shock blowing a tonque clean off... and you might die from collateral mouth/throat damage.    While a 2KV shock in the hands may give you a chance to escape with some surface damage. In the real world of accidents, it's really a random crap shoot as to what skin and organs underneath are in the path... and how long the current stays on to burn a more conductive, damaging path.

Picture a live 2KV supply - clip lead various 10 watt power resistors across it in succession.  First 1 meg... nothing happens.   Then 100K... starts to smoke after 10 seconds.  10K... explosion in 5 seconds....    1K, immediate firecraker.......   100 ohms... cherry bomb.   It all depends where on the body the current hits you.

I've read that a very large current thru the heart (> 50++ mA) will cause the heart muscles and tendons to react so violently that they literally tear themselves a part from the epileptic movements.  (The heart is designed to receive signals from the brain in the millivolt level.)  There's usually no recovery from that massive overload.  

As I get older and look at the check list to go from one big rig to another, I realize the chance to make mistakes is increasing.  Maybe the class E and SDR stuff does have a clean advantage there... :-)

T

The ubiquitous 7-16 metric coax connector system works very well for HV, is dirt cheap, too.

Good to hear you'll be OK.

73DG

Have to admit, I do not know what that is!

Pix of that connector??

               _-_-

If you do a search on ebay for   7-16 DIN, that will get a few examples of the connector.  It's available for various cables and they have chassis mounts, as mentioned, all good for HV and easy to work with.  The connector is metric, and it's not " seven sixteenths" as some call it erroneously.  Cool people just say " seven sixteen din".  The two numbers refer to the size of the inner and outer parts in millimeters.  It's a good RF connector, used by many of the moonbounce boys on arrays and dishes.   I have used them in UHF TV omni panel arrays.
It's only specified for 3 kv dc and 4 kv rf, but it hipots much higher, and it won't jump out and grab you like that Millen connector.

http://www.spectrum-et.org/new_web2/adapters/pdf/InSeries/Inseries-7-16.pdf

Thank God you're OK, Shane.  We need your wisdom and wit here... I don't think I've ever read one of your posts where I haven't learned something.  And this episode is no exception.

Thanks for sharing your experience. 

Henry used the pin jack setup for HV on some of the early 2K-3 amplifiers... They used a phenolic sleeve @ 3kv.
I rebuilt it (it was broken) using Delrin that I machined.

It fits into a corresponding connector that has the pin surrounded by a tube of phenolic, now delrin... of course
it is NOT as configured a positive locking connector. Could be made to do that, with minor mods...

The stock pin jack ends up down in the threaded delrin rod.

Sorry all I have is the 150x150px image... it's from 20 yrs back.

7-16 DIN info:

https://en.wikipedia.org/wiki/7/16_DIN_connector

Great for RF,  as well,   and as Dennis mentioned,   dirt cheap.

FWIW,   Vic

Lest we forget....

A plate modulated rig like a single 4-400A at 3KV under heavy modulation can have 6-8KV peak voltage or more... [+ dirt arc factor]  on a HV jack/plug going into the RF deck.

Linear amps are more predictable, though 6KV DC (the topic here) is dicey.

I maintain it takes extraordinary measures to safely route HV above 3KV.

T

  A modified PL-259 / SO-239 can be easily made to handle 6KV DC. Plain old RG-8 Coax (non foam insulation) can handle a lot more.

I attach a picture of the concept.

This requires some fabrication and machining, but a doable solution.

A HVDC Power Supply maker, Glassman uses this approach on a variety of products. The company I work for buys a 40KV supply that uses this approach. The RG-8 coax handles 40KV DC (not RMS AC) for years without failure. The 40KV application has the center conductor extended 14" from the connector!

This approach done proper will remove the safety hazard so prevalent with the Millen.

Jim
Wd5JKO

Now dat's wat I is talkin' bout, Jim! That is by far the BEST HV connector solution I have ever seen. It even uses the shield as a saftey feature....  cut the cable and you have an automatic short circuit to pop the breaker. And brickhouse mechanically secure.

When I build a new HV rig, the connector, cable and feeder will look like that.

Thanks for sharing it, OM!


BTW, yes, foam coax is NG for HV. I have arced it over before. Stick with the high quality (RG-213 is a good example)  clear plastic insulation as you suggested.

T

'cept for one little thing... I don't know about yooze guyz, but I do not want ANY HV on an exposed
metal plug! The banana type plug shown on the end of the coax is fine when it is connected, but
waving around a hot end, not for me. So, I'd want a FEMALE looking thing that has no easy and
direct path to the HOT conductor. That looks like the reverse of what I'd like to see.

So, that's fine for a "goezouta" not a "goezinta"!

Opinions?

                                 _-_-

I gotta agree with the Bear on that one.  HV needs to be recessed, at least a bit.  I know we all mean to be careful, but if the breaker on the HV supply is inadvertently left on, and the remote start switch (if you have one) get activated, there's trouble exposed.  At 2 AM local time, dumb stuff sometimes happens.  I'd rather see an HV line go in through a cable clamp and be permanently connected in both the HV enclosure and the RF/modulator deck.  It would be a pain and more time consuming to work on, but it could be very inexpensive, and effective.
I'm trying to think if I ever saw a commercial transmitter that had a removable connector on the HV line.  Nothing comes immediately to mind. 

Even shielded cables aren't fool proof. Try to connect one with the power on and the shield as the only return path and ZAP. Not only does it need a recessed female end, but it should make-ground-before-hot and break-hot-before-ground. Of course, a separate DC return should always be used, but accidents happen. The best bet when using a separate power supply is to put everything in an enclosed rack cabinet. That will keep you, the kids, and your pets, far from high voltages.

But even the best safe guards aren't total protection. Treat every microphone as if it's on. Treat every conductor as if it's hot. Treat every  gun as if it's loaded. Safety is more in your head than in the engineers design.

Don

Isn't it best to use connectors rated twice the expected voltage for safety?
I hate guesswork where stuff can go boom or the grim reaper lives inside.
These may not be for everyone. Not coaxial but the ratings are up there.
The plug is long and goes way into the socket and they have chassis mount.
http://hvstuff.com/high-voltage-connectors-plugs-sockets
There are others I suppose but these give you both sides of the connection.

I think Jim's idea is a good step in the right direction to getting us thinking about better HV safety.  Over the years, I've seen a lot of ham homebrew rigs. Some can be downright dangerous, especially when you look at the exposed backs of some plate modulated rigs with HV wires running from mod iron, chokes, power supplies, etc... and unshielded HV inter-connections between racks out in the open.

But then some rigs are very well done and safe. My test is this: Pretend the HV is on -  try as you may - can you touch any HV?  Can a cat or dog or child find a way to work his way into the HV if he tried?

I agree that a female banana  plug on Jim's example would be a better idea, though if there were 6 KV LIVE on a female banana plug, it would probably rock you badly if you touched it, recess or not.

I like the idea that when assembled, there is no way for Jim's plug assembly to work loose or pull out, be touched accidently, is shielded well and is so far above the required voltage, (40KV) it will (almost) never fail. (And remember to include the extra ground wire.)

Yes, commercial rigs often have permanant connections because they get installed for a long time. But most ham gear, computers and other rigs are meant to be moved from time to time and most will strip bare of cables when moved.

This homebrew plug example may cause many of us to break out of the box of old habits - Maybe we have not  been as safe as we should be.  Even though my shack passes the HV cat/dog test and uses shielded HV cables, I am looking at HV safety in a somewhat different light now.

T

Really ANY HV interconnection should be made of a screwed-on ground wire AND COAX. The BNC HV coax connectors are cheap and plentiful.  They withstand 5 kV
ANY damage of the isolation or cable will result in a HV short and the HV can never be exposed. A minor damage will expose the grounded shield, not the HV
A normal HV cable will be very dangerous when damaged.
An RG58 and the BNC HV connectors will make a low cost and safe HV connection.

When I build a box that is two pieces. I treat it like any other piece of industrial equipment. The high voltage cable is inside conduit which is grounded. I use the flexible stuff no mice kids or customers can get at it. Plus I don't get sued for building a death trap. The connections are inside the cabinet either bolted or soldered.


http://www.afcweb.com/flexible-metal-conduit/


John N8QPC

Yeah, 6 KV above ground  ;D

Good to hear you survived!  8) And watch for delayed tissue injury, as I'm sure your doc has already briefed you. HV burns and high-pressure injection injuries are always worse than they appear initially.


I have a Spellman 60 KV x-ray power supply that also uses this approach. Not designed for long-term continuous use. The jack is recessed all the way inside the "brick" and the SO-239 thread is on the other end. About 8-9" of poly RG-8 leakage path.

These look nice, but they'd be for a cable that was fixed on the RF deck side (or modulator)
and coming FROM the PS chassis. Perfect.

Going the other way, they don't seem to have a cable mounted female/chassis mounted male??

And as you noted they are not coaxial type... but one could use cable with a braid on the outside?

----------------------

DON, were you saying that in the case of HV DC on a coax cable that only has the braid grounded
on one end that it will try to arc over?? Not sure about your earlier comment...

Looks a lot like old school BX??

"gooseneck" material that they use on lamps might be interesting too... but for most applications
with semi-rigid stuff one is going to need a 90deg adapter at the ends, maybe not the best way to do things??

Then there is the flex natural gas line stuff too...

I'd be more apt to use a braid over HV rated wire.
I have 50kv rated silicone wire here. About the same size as RG-8 core, maybe slightly
fatter... I think a wire braid over the top ought to be pretty much safe??

Bear,
If the coax braid were being used as the only return for the DC, then disconnecting it (a PL259), you'd be breaking the ground connection first. If you had one hand on the connector shell and the other on the chassis... bad news.

Don

This is a very important point worth exploring further!  I have brought this up in the past and it could be the most under-rated safety guideline - that many hams do not fear...


We all put lots of care into our hot B+ lead installation.  We all make sure it is isolated both electrically and mechanically - and for good reason.

Now look at the other part of the circuit, the ground wire or B minus.   As Don said what if the ground wire gets broken OR we forget to hook it up? Considering that a lowly, bare ground wire never gets the respect it deserves, isn't it possible to make this error?


I have a question about this:

Let's take a regular linear amp. The HV B+ is basically connected to the plate of a pair of 3-500Zs. In series with the tube's plate is a near-vacuum, essentially 10? megohms or more to ground if the tube is off or unkeyed.

Let's say the chassis is floating, not grounded. (you forgot to connect up the gnd wire B- … and coax connector gnds, etc. )  Now if you put you hands across the chassis and the station ground, your body will be in series with the HV supply, in the negative lead.  X amount of voltage will drop across you depending on the ratio of the tube's vacuum and the resistance thru your arms.  Let's say you are 200K and the tube is 10 Meg+.   This puts about 60 VDC across you, not too bad.

Now, what if the tube gets keyed and drops its internal resistance... You are still 200K and the tube will struggle to drop more voltage across you.  The question is how much of the 3KV stays across the tubes with your body's series resistance of 200K?     At 200K this is 15 ma at 3KV, deadly current if the tube is keyed. Or will the 200K put the tube near cutoff and draw near zero current thru your body?   -  Am I missing something?

My point is, what are the voltages and currents involved when we get in series with the negative lead of a  standard 3KV supply into a typical linear amplifier?  Is this lowly ground wire a deadly concern we should pay more attention to?  

I suppose one way to find out for sure is hook up a 200K resistor in series with the gnd wire and measure the current and voltage across the resistor with the amp both keyed and unkeyed.  

T

And that's the reason that you ALWAYS need a screwed-on ground wire for safety return. And you also have the ground of the coax HV wire, but thats the safety in case of damage to the HV cable.
I used this years in big RF generators and never had an issue.

Admittedly, I get a little lazy about using the 10-32 grounding stud on the back of radios. A wingnut makes it a bit easier, but it's always a darn reach-around knuckle-scrapping operation that I sometimes "forget" to do. Knowing that I'm not 100% compliant with this basic requirement, I have an alternative.

On units I've built, and old boat anchors, I like to install the very common chassis mount "computer" type AC connector, IEC 60320 standard. I did this recently with a DX-100 that I'm modifying. Those connectors have a ground terminal that "makes" before the line and neutral (the ground pin is longer). The cord-set is removable, which is a blessing in itself. When servicing the radio, pulling the cord-set from the back of the rig is a good way to make sure the power source is removed, literally. These chassis mount AC inlets can be had with built-in fuses and/or RFI filters. Some even have a switch.

As an alternative to a nice heavy braid ground-strap these connectors aren't perfect. Probably not very good from an RF grounding standpoint, but pretty good for AC safety grounding. As far as I'm aware, no one has died from having a poor RF ground (not that it's not important).

So, to the point at hand, having a continuous AC ground provides a path for a broken high voltage DC return.

Two-wire non-polarized AC cords need to go.

Don

The question still remains...

Using a remote 3KV supply to power a  3-500Z linear amplifier or class C tube amplifier...  If the B minus DC ground return is broken and a human body is put in its place, (200K)  is this a lethal situation?


My current thinking is  NO....   because the 200K is in the cathode lead of the amplifier tube and acts like a big biasing resistor to cut the tube off, thus no current flow. (just like a big Zener diode normally does in the cathode)  No matter if we key the tube on or drive it with RF, the tube is still cut off with such a big cathode biasing resistance -  and the B+ 3KV drops across the tube safely and not across the "cathode resistor" human body. (with minimal "bias" shock)

Can someone tell me I'm wrong and why?

T

Tom,

I mostly agree. Probably not lethal, but probably a noticeable shock. Either way, I don't want to be a part of that circuit. What if one were operating SSB and got a small, non-lethal shock under the circumstances that you describe, that caused the usual "Ahhhhhh!" to be uttered, which then keyed the VOX. Suddenly it's not a small shock anymore.

This reminds me of a favorite movie scene from No Country for Old Men:
Llewelyn Moss: Just lookin' for what's comin'.
Poolside woman: Yeah, but no one ever sees that.

Don

Hi Don,

Thanks for the reply -

Well, I'm sticking my neck out and saying that with a 200K human body cathode resistor in the B minus, it doesn't matter if the tube is keyed, driven hard or not....  the tube is so hard-biased-off it will not draw any meaningful current to produce a B+ drop across the 200K.  There will be a "bias" voltage generated for a small jolt, if any.

It's like when we key the cathode of a linear tube to ground. When it is unkeyed, there is no soaring voltage on the cathode. This is essentially breaking the B minus.  We may use a 50K clamping resistor there, but it's only a technique to keep relay contact sparks at bay when keying. Notice we can also get away with 1KV .01 caps from cathode to ground.

I'm thinking this is why we don't hear about 50% of ham HV fatalities caused by broken ground returns and 50% caused by accidental contact between B+ and chassis.  They are almost all caused by B+ contact.   The occasional ground break fatality can happen with rock stars on stage getting 240VAC jolts, but the ham amplifier  B-  break is a different situation.

Hey, you can bet I will continue to treat B- like B+ with respect... it's just that I want to understand what is really going on and not unduly fear something that is not really there.

T

The conversation has been hams, their equipment and being safe.  What about prevention of potential "collateral damage"?

Do hams have the safety measures built into their shacks and/or equipment in an effort to eliminate or minimize the possibility of a family member or friend coming to aid the ham and getting killed themselves?  Things like emergency stop switches to de-energize the shack/rigs, built-in contactors to forcibly de-engergize or short out a power supply.  Do friends and family know what to do if that type of event happens?  Do they know how to kill power to the shack and equipment? Probably not to all of the above is my guess. 

In the context of the present discussion.....

https://www.w8ji.com/bias.htm

I believe the measured voltage 'soar' was appx 35 to 50 volts when the cathode is allowed to open with no snubber.

Definable, and would cause a little ouch....  And as stated could cause the vox to go full bore TX.   However, with the resistance of a human, I don't believe you would be subject to much more.

HOWEVER!  What we aren't taking into account is the sb220, etc. style of cut off.....  Appx 80 to 110 volts, depending in the amp...  In the case of the 220, taken from the fils xformer.

Non gg style amps have their own set of issues.  The cathode of my last 4cx style tetrode with handles was c 1300 volts negative as the screen was strapped to the chassis.

This style would be enough to make you push daisies.




Recovery is slow.  Hand hurts like all get out, and it hurts to type.....  But I am able to go to work and actually get things done.  My boss called Wed to check on me...  I said I had all the lights up, and was starting to wire them.... He replied, 'wait...  You're at work???' lol.  Yeah, I HATE sitting.

Have been back in the shop, that took a couple days.  PTSD is a bear!  Took some pics of the connector, etc....  The b+ wire is now pulled out of the connector.  It wasn't like that before the incident.....  But things did get pretty violent back there while I was trying to escape it!

There is now a large black mark on the top of the chassis as well....  It wasn't there before.  I had a thickish long sleeve work shirt (bright orange OSHA compliant THICK cotton) and a pendleton (flannel jacket for us w6 guys) on..  Neither show any marks, but I believe a lot of the energy was directed back at that spot...  There and the leg.  



Someone had mentioned how as the b+ goes up, things get more interesting.  Yes...  For sure!  I'd forgotten having built nothing but sub 7kv supplies the last few years....  The 8.5kv one I built was a whole new ball of wax.

Even the capacitor bank...  Using snap ins, I was forced to mill every non essential piece of copper off the board.  Otherwise, it would arc over. . Don't have that problem at sub 4kv.  Just mill copper pads out for the caps, with a half inch around them and your good. The 8.5 kv supply, nope.  Arc city!

The last 12kv supply was a lot of fun.  Everything mounts on glastic insulators, even the insulated equipment.


Anyway, off to bandage up the hand.  Thanks to everyone for the well wishes..  It does bring a smile to the face.

I'm also glad this has opened up a discussion about the safety of connectors, etc.   VERY glad I'm hear to be a part of said conversation!

--Shane
KD6VXI




Yes, that is my skin on the connector.  The arc grabbed me and pulled me in, just like they taught us in school.

I debated posting the pics, but I'd rather gross someone out and have saved their life by them treating hv with respect than not have posted the pics.  Sorry if it does gross anyone out, but it is truth.

My shop is entirely energized by a single breaker.

This incident brought to light:  Nobody else knew where it was or what to do.

I am installing a contactor (175 amp per pole) and the 'big red button' type disconnect at the door to do just what you describe.


I'd also add, an arc fault breaker in my panel could have been a tissue saver, although for something the size of the breaker feeding the big amps, it's cost prohibitive.

--Shane
KD6VXI

Bob,

OK, on the shack shut down advice.  Yes, I think with most of us - our ham activities are secret to the rest of the household.... :-)

My solution is that all HV supplies get keyed at the transformer primary with a step start.  Release the PTT and no HV in the shack. I never liked the sound of HV buzzing when I'm not talking.



Shane,

Yes, I can see your skin smudges.  Looks like your hand went across the aluminum panel and the point where the HV wire entered the plug. That PW HV connector assembly needs to go for sure.

T

Shane,

I edited your pictures to show Cause and Effect. I named the file "millens revenge". I think that's how the Millen HV Connector should remembered.

Don

After getting belted as mentioned in my earlier post, I've thought long and hard about this but never implemented an emergency stop system in the shack.  I have the stuff to do it but just never got around to doing it.  Probably a good time to revisit.

My wife wouldn't know what to do without education and I have been remiss in doing that. And I know if I did educate her, she'd say get another hobby.

In my previous post, I didn't think about first responders either. Something to keep in mind.

"Risky Business"

Risk perception and risk tolerance are human psychological attributes. Counter-intuitively, installing a safety device doesn't necessarily make something safer. When we perceive something as being safer, we act more casually toward it. Our perception of risk is reduced.

Shane had 'all the covers on' so he perceived the risk of electrical shock as being very low. Still, I bet a little bell went off in his head when he reached behind the equipment to a place where he couldn't see. Had he been working on unguarded equipment where dangerous voltages where clearly present, he'd have perceived the danger of shock as being very high and wouldn't have reached into somewhere that he couldn't see.

In both instances the danger is there - an exposed high voltage conductor. What changed was his perception of the risk. This isn't to say that we shouldn't install safety devices. We should. The answer is in lowering our tolerance for risk. We must learn to listen carefully to that little bell in our head that says: "Risky Business".


Respectfully submitted,

Don
KK4YY

Well said, Don.

The "little bell" in our heads is the key. No matter what we do, we need to use our lifetime of experience that has honed our intuition, pattern recognition and emotions.

"Hey, that car pulling out looks like trouble - it ain't gonna stop."  (pattern recognition warning)    

"The B+ is on and it feels scary  (emotional warning)  - I'd better use a fiberglass rod, not my hand," etc., etc.,

This is what keeps us alive for 95 years.

Frank / WA1GFZ, a man way ahead of his years, told me this story:  Whenever he turns the HV on and finds himself exposed, he sings that old cowboy song to himself... "Come a little bit closer, you're my kind of man so big and so strong.... come a little bit closer I'm all alone and the night is so long."   :-)

I find myself doing the same thing  - when close to live HV.

T

Not sure if anyone else noticed, but the center conductor of the HV wire going to
the Millen HV connector is BARE/exposed!!

and fwiw, Silicone Rubber is an effective HV insulator.

The bare insulation area wasn't like that before, that ended up getting yanked out during the event.....  But, IL bet it wasn't in all the way.

As Don said, the risk was perceived as minimal, and that was almost my death wish, so to speak.

I've been researching connectors.  The 7 16 was promising, but I have people who use that for antenna connectors, so it was a no go.

I did find this one, and it's fairly cheap in ebay.  WAY less than Millen crap. 

https://www.amphenolrf.com/connectors/mhv.html

Still doesn't solve the problem of the center pin flying, but it makes a nice easy and FRIGGIN safe connection, with ground!




And to be clear, I was reaching way behind and to the side of this, to another seating area.....  Moving the wiring away from something else...  This is not being said as an excuse, reason, etc.....  But to underscore what's being stated:  you can't be too careful!


A contactor kill switch and some serious rewiring is under plans.  Already ordered a crimp kit to make the new jumpers, etc. 

Good to see you again, Don!

--Shane
KD6VXI

   In my short time here on AMfone, this has probably been one of the most instructive threads I've followed; not because it imparts cool technical tips on designing and building better gear, but because it imparts tips on staying alive.  There are no cooler tips than that.  I've got a few pieces of older gear that I've picked up at hamfests, that use Millen connectors.  I'm thinking I'll change them out. Matter of fact, I bought a handful of Millens at recent hamfests; not saying I'll toss them, but I'll certainly apply them with greater discretion now. I'm looking into those 7/16 jobs - never heard of those before reading this thread.
   I think the takeaway here is that you can do - like the OP did - every thing right and according to the book, and still get nailed.  There's a cobra in the box, its bite is lethal, and sometimes it's not contained quite as well as we assume.
    Oddly enough, the very worst hit I ever took wasn't from HV, but only the humble 115 right from the power strip.  I was a technician at an aerospace company at the time - lots of rack mounted equipment - and I was reaching around behind a rack to pull out a power cord from a strip.  Left hand firmly planted on a bare aluminum enclosure for balance, right hand reaching for the plug.  Finger contacted the hot blade - WHOMP - up the right arm and out through the left, without pausing to enjoy the scenery as it passed through the heart.  Didn't wind up hospitalized or anything, but it shook the holy mucus out of me - had to sit down and breath slow for a few minutes - and both arms were sore for a while from the involuntary muscle contraction.  6KV or 115, it's like drowning in ten feet of water, or a hundred: dead is dead, either way.
   

I've got a couple of the old K2RIW/Arcos amps, and they use those same MHV connectors.  I like them.

I just bought these.  Take rg-6 cable, rated to 5kv and for 5 pairs at 30 bucks, I just halved my cost for cabling amps!

Finding the wire capable of withstanding that voltage level was a bit hard when searching for RG6...  Then I remembered I have some already.

It's neon sign wire.  Get the stuff rated for 'no conduit necessary' and it will come with an outer shield.  We remove it when converting from neon to led.....  🤔😁😎👌

I couldn't figure out how to share the url, so I'll include 2 screen grabs so people can see what to search for.

They make this style up to 20kv.  They have a rating for both close circuit and open circuit.   Not that I'll ever want to test the open circuit voltage rating, but it is nice to know if you accidentally have it laying in the ground, the 20kv connector wouldn't arc to anything external (like your hand, grabbing the wrong kne) until after 10kv, I believe.  Even the SHV which I bought, rated at 5kv, tested to mated 12kv and open circuit 10kv.  5 bucks a set, half the cost of Millen!

Anyway, time to go christmas shopping for the kiddos.  

Ya know, I'm usually Mr Frugal at Christmas.....  But for some reason, this year.....  The kids are gonna do well!

--Shane
KD6VXI

Shane,

You beat me to it! I was about to post this:
https://en.wikipedia.org/wiki/SHV_connector (https://en.wikipedia.org/wiki/SHV_connector)
But my wife wanted us to go out for pizza. ::)
I think you got the real deal there.

Don

Now if they could only figure out how to make a reversed gender connector like that...

I missed the shielded neon sign wire. I use GTO-15, rated 15KV, but it has no shield. I would love it to have a shield!

I have 10 and 15kv rated wire.  The 10 kv got brittle and started cracking....  The 15kv was more like spark plug wire externally....  No problems with cracking, etc.

I'll snap a couple pics when I'm out there next time.


--Shane
KD6VXI

I've got some 50kv rated wire, it's about the size of RG-8 diameter-wise and made from silicone rubber...
never heard of sheilded neon sign wire, any links to that stuff?
Does it have a "nomenclature" to search for?

I have a hunk of HV wire from an X-Ray machine....#14 stranded conductor and 1 inch outer insulation diameter...I have no idea what connector to use with it....No voltage markings.....

Seems a little overdone. X-Ray machines work upto 100 keV or more, so the wire may be rated upto 100 kV

Finally got out to the shop and grabbed a hank of the neon GTO wire I have.

It is definately coaxial, and is shielded and does not require a conduit.

It's made of two completely seperate insulators. Both are similar in feel:  The internal is like a teflon-ish material, the black one more like silicon.  Then the copper shield and then another layer of insulation.

15 kv rated.

I've not been able to find anymore online.....  Grr.

--Shane
KD6VXI

Last two pics of the labeling.

I tried kne large pic, but it made a pretty big file.

--Shane
KD6VXI

Not the same stuff, but found.

https://www.blackburnmarine.com/product/472/ancor-gto-white-high-voltage-coax-cable

Even has a pic of the braided end.

--Shane
KD6VXI

See this has been all very informative and has made me wonder if there are insulated gloves that are thick enough to provide protection, yet pliable enough to allow work on the larger elements.
Specifically I have a pair of long thick rubber gloves for use with paint stripper. Would they be helpful, or provide a sense of false security?
Shahhe, glad you are on the mend
Carl

Carl,

At work we have suits that cover you to IIRC 50 kv.

A local electrician was subjected to an arc flash from 100kv the other day!  Wow!

I have 'linesmans' gloves.  Two piece, inner is about eighth inch thick rubber gloves and the outer gloves are more 'work glove' material.

Used or left to sit, they have an expiration date.  This is to prevent injuries due to cracking.

I don't remember the rating of mine, but I think they are rated to 1 or 1.5 kv.  I won't use them on anything over 480.  Anything higher, deenergize the cabinet.  Those guys that wear the Michelin man arc suits definitely earn their money!

Heres a link to what we use at work....

https://www.thinknsa.com/admin/document/document_download.aspx?UID=7eca635e-1b76-4e38-8dc2-fcad5c02d77f

And if anyone would like to get a pair, https://www.thinknsa.com/product-category/arc-flash-ppe/arc-flash-suits-kits/rubber-voltage-glove-kits

--Shane
KD6VXI

and.. Euro stuff..
http://www.blf.it/neon-har-en50143
http://www.ceteletric.com/catalogue/speciali/ic-hv.htm

Italian, and from Venice. EN-50143 is a spec there now for HV and neon cables.

the links in other posts, Anco wire - looks about $37 for 100FT. more costly that gool ole GTO-15 but our lives are worth it, eh?

Please explain why you don't want to use normal coax? With the shield connected to ground, it is just as safe as the 37$ cable.
I used RG58 at 4 kV 1,5 Amp for many years together with the HV BNC connectors. And if you need more, there are many other types of coax like RG8, RG213 etc.

Search for "GTO neon wire" and you will see a lot of sources, including epay.

One fellow on epay says that the "other guy's" wire hardens and cracks, his is Silicone
by Technolux... fyi.  I'm searching now myself.

PA0NVD, this stuff is rated to 15kv. Also is supposed to be very flexible, a plus in some situations.

The elephant in the shack...

Now that we're paying attention to our high voltage DC wiring, how about that un-shielded, un-insulated, 600 ohm, open wire transmission line coming out of the back of the Johnson Kilowatt Matchbox? High voltage RF is as dangerous as DC - probably hurts even more!

Let's make sure we route O.W.L. where no one will be able to come in contact with it, every foot of the way from the tuner to the antenna.

Personally, I use coax.

Don

I've built power supplies to 12 kv before.  Necessitates a little better than rg58 or so.

There is quite a bit of different GTO style wire out there.  Some shielded, some not.

Turns out the shielded stuff is for marine vertical antennas.  Whodathunk that you'd need hv rated wire on a vertical?

I have aome of the stuff here that cracks.  Pulled it out of a building that had caught fire...  I wonder.



I've been but by my vertical before (on the car, ten meters) and as such always kept away from the owl.  But you bring up a good point.  Especially where it feeds through the walls.  Excellent spot for a arc, fire, etc.

--Shane
KD6VXI

It's not that big a deal but it is an improvement when volts are high and it should allow a better enclosed cable and connector.
I also like voltage ratings to be 2X what is expected for safety and for avoiding surprise repairs.
The power supply can make 6KV so whatever wire is used should be for >12KV.
Coax might be fine within its limitations. For example a few sites give 5000V RMS for RG-213. To me that's 7KV, and it is short of my 'personal' safety margin.
GTO is usually #14, more Amp rating than I need, but TV CRT lead wire is rated higher like 20-40KV, sometimes can be found NOS for cheap. I suppose a question about coax would be, what cheap coax is rated for what voltage? If it says 'request quote' then time to click X.

PE is DC rated at 20 kV/mm, PTFE at 60kV/mm. That means that RG58 has a breakdown at 36 kV. If you take a safety margin of a factor 5, which is ok for us, it will be safe at 7 kV. The current rating is max 4 Amp. including safety margin and an ambient temp of 40 degr. C. A higher current will result in degradation of safety due to heating.
There are few hams that like to transport 15 kV DC. I think is is NOT a good engineering practice to transport those voltage levels, than you need to combine all in one cabinet with there safety measures.

Farnell states the data of the manufacturer as 15 kV DC for RG 58

http://www.farnell.com/datasheets/84294.pdf

Ok, maybe I'm amazed!  ;)

Here's the app note from Spellman HV company, a big US name in HV power supplies.
Looks like lowly RG-58 is quite good @<15kvDC!!

Who knew!

Yeah, I was looking at the specs for lmr240.

BIG difference.  Lmr rated to 1.5kv!

I also read that there is a HUGE diff between dielectric used in the coass.  So that is something to be aware of as well.

I have hipot that will run up to 15kv (iirc).  Whenever I get the stones back up to go turn the hv breakers back on, maybe I'll hi pot an old piece.



As to safety ratings.  I'll have to agree with opcom.  When in towing, everything was rated at half.  They would find the breaking limit of a chain / wire rope / snatch block / whatever based upon testing.  Then half that value and that was our WLL....  Working Load Limit.  And most would take higher than that.

In looking at the HV rated stuff, the mfg are even more cautious.  The connectors I bought are tested over 10kv, but rated to 5.

--Shane
KD6VXI

Thanks, I had not found that. Since it is stated in the data I have no argument.

Where can it be had in the USA for reasonable prices?

That is too often the issue, that there is the spec, but all of them either do not show a price, or insist one buy a 500FT spool.

...any PE center insulated RG-58U should meet the spec. Belden for example.

I agree with Bear, any USA or European RG58 is ok, perhaps except the poor quality Chinese products

Week 3 pics.  Healing up.   Blisters and burned skin have almost all been flaked / sluffed / cleaned off.  The areas that are now not 'open' type wounds don't hurt anymore....  They are tender, but that's to be expected.

Have chest issues, dunno if they are related.  Going to pulmonologist, cardiologist and dermatologist as soon as my insurance approves.  Doc wants them on board in case anything pops up in the future.

Pain is about the same, 4 to 5 on the open wounds.  Since my motorcycle wreck that's pretty much life though.  I chose to go pain pill free in 2012.

In talking with my boys and yl, they seem to indicate a difference in mood / demeanor / whatever.  I seem to have gotten 'nicer'....  Not a bad thing by any means, I'll be the first to admit.

SHV connectors are almost here!  Going through soldering withdrawals!

--Shane
KD6VXI

Wow, that first picture with the yellow pus tells it all.... much more graphic than the original injury pics.

Remember my story about getting belted with 800VDC that tore open flesh on my hand, 3rd degree burns and wounds that didn't heal for months?  Yours looks like mine after 3 weeks....pus pockets that don't go away.  It's dead flesh that needs to be regrown. Keep it clean and be very patient.   Mine took over a year until people didn't notice the scars in shock.

Congrats on going pain-pill-free since 2012.   Most take the easy way out.

All the best for speedy regrowth, OM.


T

Shane,

Your experience just turned from being educational to being inspirational. Thank you for sharing it with us.

Don

One more week gone by.

My hand is really starting to come around.  Wounds have healed up and now they ITCH!  lol.

Still have to keep the burn cream / antibacterial on it.

My leg is still open.  Not a big opening....  But still raw.


--Shane
KD6VXI

Second set.

All the pics in this and my prior post where taken last night, similar time to the previous ones.....  Just didn't have time to upload last night.

Got the SHV connectors in.  Hard to not head out to the shop!

--Shane
KD6VXI

[Wounds have healed up and now they ITCH!]

That is the nerves regrowing!


Glad you are well on the mend.  All the best, Bill.

Interestingly enough (I never updated this after the fact)

This happened in Dec.  In November the following year I started having heart issues.  By December had been hospitalized once.

Started heart tests, stress tests, etc. in January.

Spent my birthday, February, in the hospital having emergency heart surgery.

One time I was on an EKG machine and had a pulse over 180.  BP was 189/110.

So you where right, Sam.  Lingering effects did happen. 

--Shane
WP2ASS / ex KD6VXI

S,

If it's any consolation, I'll never use the Millen connectors.......  I think I'll just try to crimp/bolt my HV.

klc

Mine is crimped, soldered with a shrink tube, then bolted to the cap on the RF deck. I use 30kv red flexible wire. I fed it up in a pvc channel in the rack from the PS at the bottom to the RF deck. It then connects to the plate choke/bypass cap union with a 5mm bolt into the ruskie cap. Very firm connection and not anywhere near the back of the unit. Worked out well for my needs. I had bought some of those HV BNC like connectors and decided to not use them in this situation.

For HV interface connections, I always mount  strapping standoff insulators on the chassis, usually out of reach from the back, inside the cabinet.

Shown below is my pair of 813s modulated by a pair.  The modulated B+ and modulator plate connections go through these standoffs.

Look at the right side of pic #2 to see these insulators.

T

OK.
Gotta ask.
Why the kitty pic?

klc

I purchased some of those SHV connectors as Shane recommended. However, I question the current capability of the center conducting pin. BTW I took all those connectors to work and ran them through the Megger @5KV without issues.

Hi Shane,

Wow!  Sorry to hear the delayed effects are so serious.

Exactly what damage was done?  Do you have a-fib resulting from poor heart signals from the brain or was there some actual tissue damage to the heart or surrounding areas? At this point in time, do the doctors think the open heart surgery (and other treatments) have a chance of correcting the problems?  


KLC:  Bingo - you spotted it!  The kitty picture is just one of many strange surprises hidden in my rigs ... :-).


T

Putting a harmless and even nice surprise inside gear is a time honored thing. Used to do PCBs layout on a team, and one guy always created a cartoon character in some corner.

One thing and I mentioned this on the other reflector that Shane and I both frequent is that RF Parts have these Millen  connectors listed 7KV DC @ 2A!!!!! I think they will be ok to 2~2.5KVDC but I would not push it much farther than that! Especially since his experience!

I ha e t had an ussie with current handling.  I've pushed them to well over 6kv and used in an amp that had the capability to hit 5A peaks.

18 kw out...

And I agree Mike, they should be severely derated IMHO.

This isn't the 40s anymore.  We have better methods of HV transfer.

--Shane
WP2ASS / ex KD6VXI