Speaking of dangerous stupidity, here's what I did today. I was testing
my amplifier with different plate voltages, so I was changing taps on
the primary and secondary of the plate transformer. At one point I
manged to connect the 240v line between the 220 and 240 volt terminals
instead of 0 and one of the others!
When the time delay expired there was a loud CLUNK as the 20A breaker on
the power supply, the 25A one on the wall of my shack, and the 30A one
in the service entrance all popped. I unplugged the PS and went around
resetting the breakers. Then I corrected the wiring and plugged it in again.
Some of you may know what's coming. I think I heard a faint hum (it's a
quiet Dahl transformer) but the meaning didn't register -- until I saw
the HV meter on the amp indicating 3.4 kV, with the power supply
supposedly off!
The surge had welded the contacts of the HV relay (rated 30A). Not
surprising, considering the amount of current that probably flowed
through the #10 wires connecting my shack to the service entrance.
Although I spotted the problem before it killed me, this wasn't cool. It
also proves that I need a more serious contactor for a HV relay!
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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