Disclaimer and Safety Warnings
Disclaimer
Some of the procedures described in this document
require access to dangerous voltages, hazardous laser radiation,
moving mechanical parts, and other potential risks to personal safety
and damage to equipment and property. The authors and contributors
to this document will not be held responsible for any direct or
collateral damage which might result from following the suggestions
or recommendations contained herein including but not limited to:
shock, burns, electrocution, vaporization, meltdowns, torn flesh,
destruction of the equipment, and local or planetary wide power
disruptions or implosions.
Safety
While printers are not generally considered dangerous
pieces of equipment (compared to TV, monitors, and microwave ovens,
at least), some types - laser printers in particular - present a
variety of hazards that should not be underestimated. In addition,
photocopiers - particularly larger high speed machines - need to
be treated with great respect while servicing.
There are minimal dangers in servicing most printers.
However, there may be exposed line voltage near the line cord and
long hair or neck-ties may be sucked in along with paper! Laser
printers have their lasers but these are generally located such
that accidental exposure to the beam is minimized. The toner in
copiers, plain paper faxes, and laser printers may be harmful if
inhaled and is a potential fire/explosion risk if carelessly vacuumed.
Each of these possible safety issues is discussed below with additional
specific information in the chapters for the equipment to which
it applies. All in all, working on printers is relatively low risk.
The first set of items applies to all line operated
printers:
- The input power is 110 VAC (or 220 to 240 VAC depending on where
you live). If it is necessary to work inside with the power on,
identify the location of any exposed terminals and cover them
with plastic electrical tape or block accidental access in some
other way. This is much more dangerous than the high voltage present
in laser printers and photocopiers (see below).
- Some equipment of this type uses switchmode power supplies.
Their internal voltages may exceed 300 VDC, include large capacitors,
and the entire front-end is likely line-connected. Aside from
staying away, if power problems are suspected, one must take extreme
care in troubleshooting these types of power supplies both for
personal safety and because it is extremely easy to destroy them
(and possibly the powered equipment) due to a misplaced probe.
If there is NO large power transformer near the power input but
one or more smaller transformers (possibly with HV warning labels)
amid-ships on the power board, you probably have a switcher!
- Moving parts can grab dangling neckties (yes, I know, you haven't
worn one of these in 17 years!) and jewelry - remove any you may
be wearing.
- There will be all sorts of sharp sheet metal and other parts
to gouge flesh. Avoid sudden uncontrolled movement.
- Dot matrix and thermal print heads may be HOT - stay clear.
- The inks, while probably not toxic, are certainly indelible,
so don't wear anything you care much about!
The following apply to laser printers and photocopiers:
- In addition to the AC line input, the fuser lamp is usually
powered from the line. Thus, dangerous voltage may appear (come
and go as the fuser cycles) at contacts deep inside the machine
- possibly hidden from view but not touch. The main motor drive
may also use line voltage.
- The main drive motors and gear trains in this equipment are
quite powerful, especially in large photocopiers. There is no
telling what can get sucked in due to carelessness.
- The fuser is very HOT (heat-wise) and can cause a nasty burn.
It remains hot for a long time after power is removed.
- There are several high voltages used to charge the various corona
wires. For most modern equipment, the maximum current available
from these is extremely small (less than 1 mA) so actual danger
is minimal. However, some older copiers may have more dangerous
high voltage power supplies. Don't assume all are the same! Interlocks
are *supposed* to prevent operation except when printing but they
can be defeated.
- Powdered toner is not something you want to inhale (in addition
to getting all over EVERYTHING). Also see the additional toner
warnings at the start of the chapters on laser printers and photocopiers.
- The photosensitive coating on the imaging drum may also be toxic
if it should flake off or become powdered. Avoid direct contact.
And finally, for laser printers and laser photocopiers:
- The laser in all but very old (or high performance phototypesetters
and other specialized imaging systems which this document does
not address) are IR - invisible. So, you cannot detect it by eye
- an IR tester circuit, IR detector card, some camcorders, or
other means will be needed to determine if the laser is actually
working. The beam will also be well collimated and thus especially
hazardous to vision since it will be focused to a fine point on
the retina.
Fortunately, under normal conditions, the laser beam will not
be turned on unless all interlocks are closed and a page is actually
being printed and/or will be in constant motion as a result of
the scanning mirror (which reduces the risk considerably). (It
is virtually impossible to get to the laser beam before the scanning
mirror without total disassembly.) However, certain failure modes
could result in a stationary beam which ignores the interlocks
so take care whenever working on a laser printer with the covers
removed.
- If your printer does use another type of laser (like helium-neon),
there may also be a high voltage power supply for that which can
really bite.
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