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High voltage, even when unplugged
When you turn on an amp, the capacitors are designed to
take on a charge and hold it . That stored voltage is enough
to injure you seriously, or even kill you .
These components aren’t a threat until the first time you plug
the amp in . The stored electricity can be safely discharged to
ground with a snuffer stick . See how to use it below .
Once your amp has been turned on, don’t touch the wiring
with your bare hands—even after turning it off . If you need
to press on a contact, use a chopstick or Sharpie marker,
which are both non-conductive . Don’t use a pencil, because
graphite is conductive .
It’s important that you understand the dangers so you’re
working safely . Here’s how to do it right .
Wear rubber-soled shoes
Rubber soles increase the insulation
between yourself and the ground .
Take off your ring
A metal ring on your finger can
bridge a hot connection to ground .
Wear safety glasses
Rosin-core solder sometimes bubbles up, and it can spew
molten specks into the air . You don’t want molten solder in
your eyes .
It’s better not to work alone
Electrical shocks can incapacitate you, and having someone
available to call 911 can be a lifesaver .
How to use a snuffer stick
To discharge a capacitor, clip the snuffer stick lead
to ground—preferably a mounting bolt on the
power transformer . Hold the tip of the stick to the
cap’s positive lead and use your multimeter to
watch the voltage drain to less than 18V .
Take breaks and stop when you’re tired
Fatigue leads to mistakes, and no one can afford mistakes
when working with electricity .
Stay suspicious
Whether it’s the first time you’ve been inside a live ampli-
fier or the 100th time, don’t become complacent . If you
discharge the caps and walk away for a few minutes, check
again for residual voltage when you return . Capacitors can
self-charge through a phenomenon known as dielectric
memory .
Check before powering on
It’s easy to forget that you a left a stray tool or wire in the
chassis . It’s also easy to forget to re-attach the speaker wire,
and that can fry an output transformer in seconds . Constant
vigilance is your friend when working on amps .
Always unplug it
Unplug the amp whenever you don’t specifically need it
plugged in . Some points are always hot when the amp’s
plugged in, even if the power switch is off . These points
include the lugs on the fuse socket, power switch, and
standby switch .
Amp voltages are
seriously dangerous!
Professionals
who work on
amps take these
safety habits
very
seriously
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