The worst amplifier-building injury that ever I suffered was when I was
building my first 813 amp at age 16. I was drilling a piece of copper
for a strap in the tank circuit, holding it in my hand (!) and using a
handheld drill. The drill of course caught in the copper, the strap
swung around and nearly took off a finger.
I remember thinking, "I have to be careful because the drill always
catches in copper" right before I did it. Duh.
I had a near miss with the 4Cx1000A amp I built a few years ago. Late at
night I wanted to see how it would work with slightly lower plate
voltage, so I restrapped the primary of the plate transformer.
Unfortunately, I connected the 240V to the 220 and 240 taps instead of
the 0 and 240 ones! When I turned it on, it popped the breaker in the
power supply, my shack breaker, AND the one in the service entrance, as
well as blowing the fuses in the PS.
After resetting all the breakers, replacing the fuses and fixing my
error, I plugged it back in. Although it was turned off, the plate
voltage meter swung up to 3600V! Turns out the primary relay was welded
shut.
73,
Vic, 4X6GP
Rehovot, Israel
Formerly K2VCO
http://www.qsl.net/k2vco/
On 8 Jan 2017 08:33, Roger (K8RI) wrote:
I mentioned my first project was a pair of 6L6s, that probably had
between 500 and 600 volts on the plates. By the time I was building the
6C21 into a pair of 813s, I was working on RF generators, some of which
developed over 200 KW. As I was in maintenance they just assumed I knew
what I was doing. Back then all the training and safety procedures
weren't required.
I would have been as safe building QRO at 15 as I was at 50.
On the farm, I was operating machinery that could snuff you out in a
really messy fashion. Equipment that you wouldn't dare let a youngster
operate nowdays or the law would pay you a visit. That was normal for
farm kids in those days.
So I had learned a healthy respect for anything that hurt including Weed
Chopper electric fences. I knew what HV could do, before ever getting
near it.
73, Roger (K8RI)
On 1/7/2017 11:14 AM, Ward Silver wrote:
> Excellent advice, Jim.
Hear, hear!
And another good piece of advice is to make sure you have an ac safety
ground connection on every metal enclosure. With 12 Vdc being the
normal power supply voltage these days, we can get away with practices
that would really be hazardous for tube-based gear.
> A 50 uF capacitor charged to 4000 V holds a potentially deadly 400
Joules of energy
In the defibrillator business of a few years ago, this was known as
the "rescue shock" of last resort. This amount of energy can lift a
200-pound person 1.5 feet. When leveraged by muscle-and-bone, much
damage can be done.
73, Ward N0AX
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|