Also see the document: Safety Guidelines for High
Voltage and/or Line Powered Equipment.
|Printer and Photocopier Troubleshooting and Repair Collection : SAFETY
1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.
I may be contacted via the Sci.Electronics.Repair FAQ (www.repairfaq.org) Email Links Page.
<< DISCLAIMER |
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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! See the document:
Notes on the Troubleshooting and Repair of Small
Switchmode Power Supplies for more information.
- 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
- 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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