It appears that a number of ZS-types have acquainted themselves with the
HT of PAs and survived, despite being blown across the room. This seems
to be the ultimate safety interlock.
Reliance on interlocks and switches changes the mindset to "cowboy" and
that is dangerous.
A friend working on the high power klystron (EHT 10-16 kV?) of a Marconi
troposcatter network in Libya believed that the door interlocks were
activated until he touched the EHT. They weren't, his mate has
overridden them with jams.
He survived, despite a CPU reset and holes in the soles of his shoes.
Of course, there are times when one HAS to work on a PA that is powered,
but there are special rules to follow and the risks are high even for
qualified persons....
Component ID is priority: example; that HT post in the input tuning
compartment of the SB 220 would keep undertakers smiling.
Ian ZS6BTE
Edward Ewell wrote:
>
> Ed Ewell wrote:
>
> I agree very much, the hazard is not the design of the equipment, but the
> weakness is in the procedures?
>
> Most amplifiers on stand by, the tubes or transistors do not draw
> current, they
> are biased off. (I say most) however going from stand by to operate the bias
> voltage
>
> goes to operating bias level, drive is applied to the amplifier and things
> work.
>
> However all of the time the circuit is alive, just different voltage
> levels....
>
> When you take the cover off an amplifier, you are looking at death
> straight
> on. Life is fairly long, death is instant. (If interlocks are activated the
> amplifier
> will possibly be dead? don't count on it?)
>
> Do not place your hand in an amplifier with the power plug in the wall?
> You are
> asking for it.
>
> If you are experienced, you will place one hand in your pocket when
> reading
> voltages, best
> is to power down, attach meter leads (with plug removed from wall socket),
> then power
> up.
>
> Amplifiers are very powerful, but most dangerous, have some one help that
> is
> experienced,
> or ask.
>
> Commenting on a stand by switch, is not wrong, but only asking for an
> explanation. This
> thread of experienced and helpful communication people is the best place for
> information.
>
> Ed K7DXV Oregon...
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