A not so gentle reminder - HV is unforgiving

[Gerry VanLoh]

Whew Dave, glad you're ok!  All warnings here are to be taken
seriously.  Another thing I learned is to never provide that path
THROUGH yourself either.  As a broadcast engineer for years, I developed
the 6th sense to NEVER touch another part of the chassis with your other
hand or whatever, while digging, even in equipment that is OFF. That bit
of current through your chest cavity can do you in even worse so
beware.  On larger equipment it's so easy to lean against it with your
knee or shoulder and the rest could be bad news if you contact something
live.  Always treat it as if it's not discharged, use your grounded
discharge lines, etc when digging inside.  I just opened up an SB-200
here for the first time also, but it got a shorting bar (ok,
screwdriver) across things before I started digging.. and this thing has
been off for months.  Just can't bring myself to digging inside without
knowing it's discharged.

As for being bit, yeah, a broadcast tx did that once.. all with
grounding rods in place and after I went over things with shorting bar!
I think a screen circuit on a driver tube kept a charge and when I
touched it (no path to ground from other body parts) it kicked me out
and against the wall and left me pretty upset!  Broadcast people always
do this in the middle of the night, under stress and ALONE.  Stupid!

Well, I work with computer networks these days.  Other stress.  ;-)

Just take care around the tubes guys!  I've heard the stories of people
expiring from accidents around the simplest of circuits so watch it.

73
Gerry

Steve Harrison wrote:
>
> At 12:47 AM 11/27/98 -0500, David Humbertson wrote:
>
> >...Spent most of the day putting the finishing touches on a very
> >nice SB-200 I just picked up - had put the top shield on and
> >just had it on the bench "burning in" this evening as my family
> >and I had our Thanksgiving dinner etc. I went downstairs to my
> >BA bench to give it a look and for some reason I put my right hand
> >on the right side, feeling for heat from the bleeder resistors safely
> >inside. My little finger must have curled under a bit and what
> >happened next is just a blur as it came in contact with the 2400
> >volt runner on the outside edge of the PS board -
>
> .... apparently, you left it running, UNATTENDED, on the bench, WITHOUT THE
> COVER??!!
>
> I don't know how many there are in your family; their ages (small, curious
> ones, perhaps?), or whether you have any pets; but the only time I would
> think it permissible to leave a HV PS running in the open like that while
> completely unattended is...
>
> NEVER!!! Under ANY circumstances! PARTICULARLY with no safety shields in
> place!
>
> What if something happened to you at the dinner table: the knife slipped,
> or you collapsed, and you wound up incapacitated; how would any family
> member or emergency squad personnel know what to do about whatever you may
> have left running? How would ANY of them even know that amplifier was
> super-dangerous to the unknowing? In their rush to turn it off, they might
> lean over it to pull the plug from the wall, even after hitting the ON/OFF
> switch. Feeling the heat radiating from it, they might even try to handle
> it to see whether there was danger of a fire somewhere. BEFORE the HV bled
> down, not knowing anything about slow discharge of HV power supplies. With
> BOTH hands.
>
> What if something had begun arcing, spitting little balls of molten metal
> all over the workbench while you were gone, starting a fire... on
> Thanksgiving Day, yet.
>
> No, I just can't conceive of a circumstance that would warrant the terrible
> risk of leaving something like that running, especially with others in the
> house who might have no idea whatsoever how to handle the equipment.
>
> We're all glad that you related this story to us, Dave... we know it was
> painful (in more ways than one). Hopefully, the rest of us will now begin
> to think a bit deeper, and a bit further ahead, about what we're doing when
> we're working on our BAs. No doubt about it: these BAs can represent a
> life-threatening danger to many of today's generation who are unaccustomed
> to tube equipment with their necessary high voltage power supplies, not
> just to folks like ourselves who love and work on it with such familiarity
> and abandon.
>
> By choosing to "play" with BAs, I think we have all unwittingly taken on a
> new responsibility that, because of the equipment age and thus unfamiliar
> technology to today's generation, we may have never considered before: this
> equipment can present unfamiliar dangers to many others, whether within or
> outside our own families, whether emergency personnel or the curious. We
> should try to keep that in mind at all times; and by doing so, we will only
> make our own actions safer to ourselves, too.
>
> 73, Steve Ko0U/1
>
> P.S. Yes, I've had my own jolt: I was thrown clear across my bedroom some
> 30 years ago while I was playing INSIDE my 4-1000 amplifier. Hasn't
> happened since so I guess I'm due for another "reminder"...
>
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WAØJCV

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