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Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools

Contents:


  6.23) Repair of broken heating elements


In appliances like waffle irons and toaster ovens, these are usually welded.
This is necessary to withstand the high temperatures and it is cheap and
reliable as well.  Welding is not normally an option for the doit yourselfer.  
However, if you are somewhat suicidal, see the section: "Improvised welding repair of heating elements" for a more drastic approach.

I have used nuts and bolts, say 6-32, bolt, wire, washer, wire, washer,
lockwasher, nut.  Depending on how close to the actual really hot element
it is, this may work.  If you are connecting to the coiled element, leave
a straight section near the joint - it won't get as hot.

The use of high temperature solder or brazing might also work.

The best approach is probably to use high temperature crimp connectors:

(The following from: sad@garcia.efn.org (Stephen Dunbar))

You can connect heating element wires with high-temperature solderless
connectors that are crimped onto the wires. Be sure to get the special
high-temp connectors; the ordinary kind will rapidly oxidize and fall apart at
high temperatures. If you want to join two wires to each other, you'll need
either a butt splice connector (joins the wires end-to-end) or a parallel
splice connector (the wires go into the connector side-by-side). To fasten
a wire to a screw terminal you can use a ring or spade connector (though
as noted above, a screw, nut, and washer(s) should work fine --- sam). If your
waffle iron has quick disconnect terminals you'll need the opposite gender
disconnect (AKA Faston). These come in both .187" and .250" widths. 

Your best bet for getting these connectors in small quantity is probably a
local appliance parts outlet that caters to do-it-yourselfers. If you can't
find what you need there, try Newark Electronics (branches all over the
place). I have an old copy of their catalog which lists SPC Technology
Voltrex Brand High Temperature Barrel Terminals in several styles: ring,
spade, disconnect, and butt splice. The prices were around $10 to $12 per
100 (this catalog is a couple of years old) for wires in the 22-18 or
16-14AWG size ranges, almost twice that for the heftier wire gauges. (Be
sure to determine the wire gauge of your heating elements so you can get the
right size terminal.) 

You can spend a *lot* of money on crimp tools, but for occasional light use
you can probably get by with one of those $10 gadgets that crimp, strip &
cut wires, and cut bolts--the sort of thing you'd find in your local home
center or Radio Shack.

(From: Nigel Cook (diverse@tcp.co.uk)).

The thin stainless steel strip found spot welded to multicell NiCd batteries
make good crimps for joining breaks in heater resistance wire.  Form a small
length of this strip around a needle or something similar to make a tight
spiral with enough clearance to go over doubled-up heater wire.  Abraid or
file the cut ends of the broken wire.  Crimp into place with a double lever
action crimper.  If there is an area of brittle heating element around the
break then cut out and splice in a replacement section with two such crimps.
Such a repair to my hot-air paint stripper (indispensable tool in my
electronics tool-kit) has survived at least 50 hours.

(From: Dan Sternberg (steberg@erols.com)).

Another old trick for nichrome repair is to make a paste of Borax, twist the
two broken end together, and energize the circuit.  A form of bond welding
takes place.  I've have used this on electric clothes dryer heater elements
with good luck.


  6.24) Solenoids - small and large


Solenoids are actuators operated by electromagnets that are used to operate
valves, slide or engage various parts, eject or prevent opening of a door,
and other functions.  While shapes and sizes may vary, all electrically
operated solenoids use an electromagnet - AC or DC - to pull on a movable
piece called an armature which generally moves back and forth but rotary
motion is also possible.

Solenoids are usually two position devices - they are not used to provide
intermediate amounts of force or travel like motors.

Sizes ranges from small 1/2" long units providing a fraction of an ounce of
force and 1/8" travel to large 3" long units providing many pounds of force
with travels of 2" or more.

Testing: Inspect for free movement.  Use an ohmmeter to confirm that the
coil is intact.  There could be other problems like shorted turns in the
coil but these would be less common than lack of lubrication or an open
coil.  Check voltage on operating solenoid to determine whether drive power
is present.


  6.25) Small electronic components - resistors, capacitors, diodes


A variety of small electronic components may be found in appliances though
unlike true electronic equipment, these do not usually run the show.

Resistors - may be used in various ways to adjust the current flowing in
part of a circuit.  Many different types of resistors are possible - tiny
carbon or metal film types looking like small cylindrical objects often
with colored bands which indicate the value.

Power resistors - larger cylindrical or rectangular often ceramic coated.
These may get quite hot during operation.  Their resistance value and power
rating are usually printed on the resistor.

Capacitors - a variety of shapes and sizes.  Some may look like disks,
jelly beans, cylinders, boxes, etc.  Their value is often marked in uF or pF.

Diodes or rectifiers - solid state devices that permit electric current
to only flow in one direction (positive current in the direction of the
arrow when marked this way).  These are most often used in appliances to
change AC to DC or to cut the power to a motor or heater (by allowing only
half of the AC current to pass).

For more information on these types of components, see any good introductory
electronics text.


  6.26) Motors - universal, induction, DC, timing


A large part of the functionality of modern appliances is based on the
use of motors of one form or another.  We devote an entire chapter to
motors.  The following is just an introduction.

Motors come in all shapes and sizes but most found in small appliances
can be classified into 5 groups:

        1. Universal motors.
        2. Single phase induction motors
        3. Shaded pole induction motors.
        4. Small permanent magnet DC motors.
        5. DC brushless motors.
        6. Synchronous timing motors.

See the chapter: "Motors 101" for more detailed information on the common
types of motors found in small appliances.


  6.27) Fans and Blowers - bladed or centrifugal


The entire purpose of a particular appliance may be to move air or this
may simply be needed for cooling.  Obviously, portable and window fans
are an example of the former.  However, many appliances have built in fans
you may not even be aware of as part of the motor(s) or other rotating
components.

There are two primary types of configurations:

1. Bladed fans - we are all familiar with the common desk or window fan.
   This uses a set of rotating blades - typically 3-5 to gather and direct
   air.  In the specific case of an oscillating desk fan, a gear drive
   linked to the motor also permits the general direction of air movement
   to be controlled in a back-and-forth motion.  I recently saw one where
   in addition to moving back and forth, the front grille can be set to
   rotate at an adjustable rate providing more variation in air flow.

   The direction of the air movement with respect to blade rotation is
   determined by the pitch - the tilt - of the blades.  Although reversing
   air direction is possible by reversing the motor, one direction is usually
   more effective than the other due to the curve of the blades.

2. Centrifugal blowers.  These use a structure that looks similar to a
   squirrel cage to suck air from the center and direct it out a plenum
   formed around the blower.  While these may be found in all sizes, the
   most common household application is in the vacuum cleaner.  Large
   versions of these blowers are used in central heating and airconditioning
   systems, window airconditioners, and oil burners.

   Direction of rotation of the blower motor does not change the direction
   of airflow.  However, one direction will be more effective than the
   other (where the blower is rotating in the same direction as the way exit
   port on the air plenum points.  Because of this, it is not possible for a
   vacuum cleaner to blow out the suction hose due to a reversed motor (which
   in itself is for all intents and purposes, impossible as well).  This is
   usually caused by back flow due to a blockage.


  6.28) Bearings and bushings


The shafts of rotating parts normally are mounted in such a way that friction
is minimized - to the extent needed for the application.  A bearing is any such
joint with more specific terms used to describe the typical types found in
small appliances - or lawnmower, automobile engines, or 100 MW turbines.

Plain bearings - these consist of an outer sleeve called a bushing in which
a polished shaft rotates.  The bushing may be made of a metal like brass or
bronze or a plastic material like Teflon(tm).  The shaft is usually made of
steel though other materials may be found depending on the particular needs.
Where a metal bushing is used, there must be means provided for lubrication.
This may take the form of oiling grooves or holes and an oil reservoir (usually
a saturated wad of felt) or the bushing itself may be sintered.   Metal
particles are compressed at high temperature and pressure resulting in a
very porous but strong material which retains the lubricating oil.

Under normal conditions, a plain bearing wears only during start and stop
cycles.  While the shaft is rotating at any reasonable speed, there is no
metal to metal contact and thus no wear.  With a properly designed and
maintained bearing of this type, a very thin oil film entirely supports
the shaft - thus the importance of clean oil.  Your automobile engine's
crankshaft is entirely supported by these types of bearings.

Eventually, even 'lubricated for life' bearings of this type may need to be
disassembled, cleaned, and lubricated.  The plain bearings in small appliances
must be lubricated using a proper light oil like electric motor or machine
oil - not automotive engine oil and NEVER NEVER WD40.

NEVER, ever, use WD40 as a lubricant (unless specifically recommended by the
manufacturer of the equipment, that is)!  WD40 is not a good lubricant despite
the claims on the label.  Legend has it that the WD actually is an abbreviation
for Water Displacer - which is one of the functions of WD40 when used to coat
tools.  WD40 is much too thin to do any good as a general lubricant and will
quickly collect dirt and dry up.  It is also quite flammable and a pretty good
solvent - there is no telling what will be affected by this.

WD40 has its uses but lubrication unless specifically recommended by the
manufacturer (of the equipment, that is) is not one of them.  Results initially
may be good with that instant gratification that comes from something returning
to life.  However, the lighter fractions of WD40 evaporate in a few days 

For very small metal-in-plastic types, the following might be useful:

(From: Frank MacLachlan (fpm@bach.n2.net)).

"I've had good luck with a spray lubricant called SuperLube.  It contains a
 solvent which evaporates and leaves a Teflon film which doesn't migrate
 or retain dust.  I spray some into a spray paint cap and then apply the
 solution with a toothpick, allowing the lubricant to wick into the bearing
 areas.  Worked great for some balky Logitech mice I purchased at a local
 swap meet."

Frictionless bearings are usually of the ball or roller variety.  An inner
ring called a race rotates supported by a series of balls or rollers inside
an outer race.  There is virtually no friction even at stand-still with these
bearings.  However, rolling metal to metal contact is maintained at all speeds
so they are not quite as wear free as a properly maintained and constantly
rotating plain bearing.  However, for all practical purposes in small
appliances, these will last a long time and are rarely a problem.

Sometimes, reworking an appliance to use a ball bearing instead of a plain
bearing is a worthwhile effort - I have done this with electric drills and
shop vacs.  They run smoother and quieter with ball bearings.  Not
surprisingly, higher-end models of these devices (which use ball bearings)
share parts with the cheaper versions and finding standard ball bearings
that would fit was not difficult.


  6.29) Mechanical controllers - timing motors and cam switches


While these are not that common on small appliances, they may be present
in washing machines, dryers, dishwashers. and refrigerator defrost timers.
They in themselves may be considered small appliances - and often can be
repaired or replaced easily.

Most of these are just small timing motors (synchronous motors running
off of the AC line) which rotate one or more cams (disks with bumps) which
activated one or more switches at appropriate times during the rotation
cycle.  Typical cycle times range from a minute or less to several hours
(refrigerator defrost timer).  Most like washing machine timers are in
the 1 hour range.  Sometimes, the motor is stopped during certain portions
of the cycle awaiting completion of some other operation (i.e., fill).

These controllers therefore consist of several parts:

* Timing motor.  A very small synchronous AC line operated motor with
  an integral gear train is most common.  Sometimes, the rotor and
  geartrain are in a sealed, easily replaceable unit - a little metal
  case that clamps within the pole pieces of the AC field magnet.  In
  other cases, it is a separate motor assembly or an integral part of
  the overall timer mechanism.

* Escapement (not present on all types).  This is a device which converts
  the continuous rotation of the timing motor to a rapid movement for each
  incremental cam position.  A common type is a movement every 45 seconds
  to the next position.  This assures that the make or break action of the
  switches is rapid minimizing arcing.

* Cam(s).  One or more cams made of fiber composite, plastic, or metal,
  are rotated on a common shaft.  There will be one set of switch contacts
  for each circuit that needs to be controlled.

* Switches.  These will either be exposed sets of contacts or enclosed
  'microswitches' which are operated by the cams.

Testing: If the controller is not working at all, check for power to the
motor. Listen for the sound of the motor parts rotating.  Check for gummed
up lubrication or broken parts.

If some of the circuits do not work, check the switches for dirty or worn
contacts or broken parts.


  6.30) Electronic controllers - simple delay or microprocessor based


These can range from a simple R-C (resistance-capacitance) circuit to
provide the time delay in a toaster to sophisticated microprocessor based
systems for programming of a coffee maker or microwave oven.

While generally quite reliable, bad solder connections are always a
possibility as well as failed parts due to operation in an environment
prone to temperature extremes.

Testing: Check for bad solder connections and connectors that need to
be cleaned and reseated.  Inspect for obviously broken or burned parts.
Test components for proper value.

For digital clock/programmers or  microprocessor based controllers, not
much else can be done without a schematic - which not likely to be easily
available.


  6.31) Batteries - Alkaline, Lithium, Nickel-Cadmium, Lead-acid


More and more small appliances and power tools are cutting their
cords and going to battery power.  Although there are a large number
of battery types, the most common for power applications (as opposed
to hearing aids, for example) are:

* Alkaline - primary (non-rechargeable, for the most part), long shelf life,
  high energy density.

* Lithium - primary and secondary (rechargeable) available though most
  appliance applications (which are just beginning to develop) are not
  rechargeable.  Long shelf life, very high energy density.  Still quite
  expensive.

* Nickel Cadmium - most common rechargeable technology in cordless appliances
  and power tools.  However, relatively fast self discharge and on about
  half the capacity of a similar sized Alkaline.

* Lead-Acid - secondary type similar to the battery in your automobile
  but packaged in a totally sealed container which is virtually indestructible
  and leakproof.  Medium self discharge rate but will deteriorate if left
  discharged for an extended period of time.

See the chapter: "Batteries" for more information.


  6.32) AC adapters and chargers - wall 'warts' with AC or DC outputs


These wall adapters are used to power many small electronic devices and
appliances directly and/or to recharge their batteries.  They usually
plug directly into the wall socket and convert the 115 VAC (U.S.) to a
lower voltage - 3 V to 24 V AC or DC typical.  More sophisticated units
may actually be a switching power supply with smart electronic control of
battery charging and power management.   The following are typical types:

* AC output - 3 to 24 VAC (or more) at 50 mA to 3 A.  The only internal
  component is a power transformer which may include a thermal or ordinary
  fuse for protection.

* DC output - 3 to 24 VDC (or more, under load) at 50 mA to 1.5 A.  In
  addition to the power transformer, there is a rectifier, filter capacitor,
  and possibly a three terminal IC regulator (not that common).  Some type
  of protection will probably be built in as well.

* Universal/switching power supply - typically 6 to 18 VDC at .5 to 3 A.
  These will usually operate off of any voltage input from 90 to 240 VAC
  (or DC) and provide a well regulator output.  There will generally be 
  an internal fuse as well as overvoltage and overcurrent protection.

In some cases, a single adapter will put out multiple voltages.  See the
chapter: "AC Adapters and Transformers" for more information.


Chapter 7) AC Line and Battery Powered Household Appliances



  7.1) Table lamps


This is the most popular type of lighting for reading or general illumination.
The type described in this section takes normal 115 VAC light bulbs.

The common table lamp is just a light duty cordset, switch, and sockets
for one or more incandescent light bulbs.  In many cases, the switch and
socket are combined into one assembly.  In other designs, particularly
where more than one bulb can be lit independently (for example, a large
bulb up top and a night light in the base), a separate switch (rotary or
push-push) selects the light bulb(s) to be turned on.

For the most common combined switch and socket, there are several varieties
and these are all generally interchangeable.  Therefore, if you want to take
advantage of the added convenience of a 3-way bulb allowing low, medium, and
high illumination, it is a simple matter to replace the simple on-off
switch in your lamp with a 3-way switch (not to be confused with the 3-way
switches used in house wiring to control a single light fixture from 2 places).

Push-push, pull chain, and rotary switches are common for simple on-off
control.  The 3-way switches are usually of the rotary variety with
off-low-medium-high selected as the knob is rotated.  The 3-way bulb has
two filaments which can be switched on individually or in combination to
provide the 3 levels of illumination.

Dimmer sockets can often be substituted for the normal kind as long as
conventional incandescent bulbs (and not compact fluorescents) are to
be used.

Touch and even sound activated switch-sockets are also available though
my personal recommendation is to stay away from them.

Most common problems: burned out bulb, worn switch, bad plug or cord.
Where the light flickers, particularly if jiggling or tapping on the
switch has an effect, a bad switch is almost always the problem.  Switch
failure is more common when using high wattage bulbs but can occur just
due to normal wear and tear.

Replacements for most common switches and sockets are readily available at
large hardware stores, home centers, and electrical supply houses.  It is
best to take along the old switch so that an exact match (if desired) can
be obtained.  While the thread sizes for the screw on socket shells are
quite standard, some older lamps may have an unusual size.  For more
complicated switches with multiple sockets, label or otherwise record the
wiring.  If color coded, cut the wires so that the colors are retained
at both the lamp and switch ends.


  7.2) Rebuilding a basic table lamp


As noted in the Introduction, virtually any table lamp can be restored
to like-new electrical condition for a few dollars at most.  The following
is the detailed procedure for the majority of common table lamps found
in the U.S.

This is assumed to be the type of lamp which has a combination socket and
switch with a metal (brass-colored usually) outer shell.  It is your decision 
as to whether a simple on-off switch or a 3-way type is to be used - they are
usually interchangeable and a normal light bulb can be put into a 3-way socket
(two clicks of the knob will be needed to switch a normal light bulb on or off,
however).  You can also put a 3-way bulb into a normal socket but you will, of
course, only get one level of illumination (medium).  For lamps with lighted
bases, also see the section: "Lamps with night-light bulbs in their base".

You will need: (1) a new socket/switch of the appropriate type and (2) a
new cordset (if you want to replace this as well).  A polarized type plug
is desirable to minimize the possibility of shock when changing bulbs.  A
medium size straight blade screwdriver and wire strippers are the only
required tools.

First, remove and set aside any shade, frosted chimney, and other cosmetic
attachments.

Unplug the lamp!!!

Examining the metal shell, you will note that it is in two pieces.  If you
look carefully, there will probably be indications of where firmly pressing
the top portion will allow it to be separated from the bottom part mounted
on the lamp.  These are usually near where the knob, button, or chain, enters
the switch.  Sometimes, a fine screwdriver blade will be useful to gently
pry the two halves apart.

With the top part removed, unscrew and disconnect two wires and remove
the switch.  If desired, loosen the set screw (if any) and unscrew the
bottom portion of the shell.  If you are simply replacing the switch, at
this point you would just attach the new one and reassemble in reverse
order.  Screw on the bottom of the new switch enough so that it is either
tight or until the threads are fully engaged but not pressing on or protruding
above the cardboard insulating disk in the bottom half of the shell.  If
the entire assembly is still loose, it should be possible to tighten hardware
on the bottom of the lamp to secure it against rotation.  Note: it is
important to do this to avoid eventual damage to the wires should the switch
move around significantly during normal use.

To replace the cordset, you may need to partially remove any felt pad
that may be glued to the base of the lamp.  Sometimes, it is possible to
cut off the old plug, attach the new cord to the end of these wires, and
pull it through.  However, in most cases, there will be a knot or other
strain relief in the original cord which will make this impossible (and
you will want to replicate this in the replacement as well).  Therefore,
if needed, carefully peel back the felt pad only enough to gain access to
the interior.  In some cases, just cutting a small X in the center will
allow sufficient access and this can be easily patched with a piece of
cloth tape.

Install the new cord in exactly the same way as the original with a knot
for a strain relief if needed.  If there was no strain relief to begin
with, adding a knot is a good idea if there is space for one in the base.
Snake the cord through to the top of the lamp.

Strip the ends of the wires to a length of about 1/2 inch and twist the
strands tightly together in a clockwise direction.  If you are using a
cordset with a polarized plug, identify the wire attached to the wide
prong (with a continuity checker or ohmmeter if it is not clearly marked
by a stripe on the insulation) and connect it to the silver colored screw.
Connect the wire attached to the narrow prong to the brass colored screw.
Always wrap in a clockwise direction.  See the section: "Attaching wires to screw terminals".

Confirm that there are no loose wire strands and that the insulation is
nearly flush with the screw to avoid possible shorts.  Pop the shell top
with its insulating cardboard sleeve over the switch and press firmly onto
the base.  There should be a very distinct click as it locks in place.

If needed, adjust the strain relief at the base of the lamp so that pulling
on the cord does not apply any tension to the wires attached to the switch.
Tighten the nut in the base of the lamp holding the entire assembly in place
if the socket is still loose and rotates easily.  Don't overdo it - the
supporting structure is often just a glass jar or something similar.  Put
a drop of Loctite, nail polish, Duco cement, or something similar - or a
second nut - on the threads to prevent the nut from loosening.  Use some
household cement to reattach the felt pad you peeled back earlier.


  7.3) Lamps with night-light bulbs in their base


These are the types of lamps where either the normal bulb on top or a smaller
one in the base (or both) can be turned on using a turn-key or pull-chain.

This is a standard, if somewhat unusual socket.  It is basically the same
as a 3-way type but with the extra connection going to the bulb in the base
of the lamp.  In the old days when sockets were assembled with screws instead
of rivets, it might have been possible to modify a new 3-way socket to provide
the extra connection.

An electrical supply parts distributor or lamp store should have what you need
or be able to order it for you.

Take note of the connections as you remove the old socket to avoid mistakes.
When routing the wires to the bulb in the base, avoid allowing the hot bulb
from contacting the insulation - the plastic stuff might melt (for a 7 W or
less wattage bulb and high temperature insulation is probably not an issue,
however).


  7.4) High intensity lamps


These include several types but they all use a transformer to reduce the
115 VAC to something lower like 12-24 V.

Tensor(tm) (and their clones) high intensity lamps have been around for
over 30 years and are essentially unchanged today.  They use a low voltage
transformer producing 12-24 VAC along with a special high output light bulb
that looks similar to an automotive tail light.  However, it uses substantially
more current for the same voltage and puts out a much more intense, whiter
light.  These are not halogen lamps though their spectral characteristics are
similar since the filaments run hotter than normal incandescents - and have
shorter lives.

Some will have multiple levels of illumination based on selecting taps on
the transformer.  Normal dimmers may not work (and should not be used) with
these due to their transformer design - damage to the dimmer or lamp may
result and this may be a fire hazard.

Problems with Tensor lamps tend to center around the socket and switch.
These may fail due to overheating as a result of the high temperature and
high current operation.  Replacements are available but they may take some
effort to locate.  A replacement lamp may be cheaper.  (I often find complete
Tensor lamps in perfect operating condition at garage sales for around $2.


  7.5) Halogen lamps and fixtures


Halogen lamps share many of the design characteristics of high intensity
lamps in that they are designed for local high intensity lighting and use a
transformer usually (though some may use solid state voltage conversion
instead).  While some halogen lamps come with dimmers, some of the advantages
of the halogen cycle are lost if the bulbs are not run at full power.  The
worst case is where they are operated just below full power - too cool for
the halogen cycle to take place but hot enough for substantial filament
evaporation to occur.

Should the dimmer portion of such a fixture fail or become unreliable, it may
a blessing in disguise since the lamp will either run at full intensity or can
be easily rewired to do so by bypassing the electronics and just using the
on/off switch!

WARNING: halogen bulbs run extremely hot and are a serious fire hazard and
burn hazard if not properly enclosed.  When changing a halogen bulb, wait
ample time for the old one to cool or use an insulated non-flammable glove
or pad to remove it.  When installing the new bulb, make sure power is off,
and do not touch it with your fingers - use a clean cloth or fresh paper
towel.  If you do accidentally touch it, clean with alcohol.  Otherwise,
finger oils may etch the quartz and result in early - possibly explosive
failure - due to weakening of the quartz envelope.


  7.6) Safety guidelines for use of halogen lamps


These guidelines were prompted by a number of fires including some fatalities
that have been linked to improper use of halogen lamps - in particular the
high power torchiere variety of floor lamps.  However, the guidelines apply
to many other types of halogen lamps including work-lights, desk lamps, slide
and overhead projectors, and other lamps or fixtures where the bulb is not
entirely enclosed and thermally insulated from the exterior.

(Source: The Associate Press except as noted).

Safety groups recommend the following precautions for owners of halogen
torchere lamps with tubular bulbs:

* Place the lamps where they cannot be tipped over by children, pets, or
  strong drafts (away from open windows, for example).

* Never use halogen lamps in children's bedrooms or playrooms where combustible
  objects like stuffed toys may be accidentally placed on top of or next to
  them.

* Never use a replacement bulb of a higher wattage or of a different type
  than specified by the manufacturer.  Avoid bulbs larger than 300 W.

* Never attempt to replace or discard a bulb that is too hot to touch.

  Do not touch the new bulb with your fingers as the oils and acids may make
  them more prone to exploding.  Clean the bulb thoroughly with isopropyl
  alcohol after any accidental contact (--- sam).

* Never drape cloth over the lamp.

* Operate the lamps at less than maximum wattage on a dimmer whenever possible.

  Note that this may not result in maximum life but will be safer due to the
  lower temperature of the bulb (--- sam).

* Keep lamps away from elevated beds like bunk beds where the bedding may get
  too close to the bulb.

* Never use unprotected halogen lamps in locations like bathrooms where water
  may splash resulting in the bulb exploding (--- sam).

* Never operate lamps with their thermal or UV shields removed (--- sam).


  7.7) What causes a lamp to flicker?


Many things can cause the light bulb in a table lamp to flicker:

* Loose bulb(s) :-).

* Bad switch.  These do wear out particularly if multiple high wattage bulbs
  are being used.  If gently jiggling the switch results in flickering this
  is the most likely cause.

* Bad connections.  These could be anywhere but the most likely locations
  (where only a single lamp is involved) would be either at the screw
  terminals on the switch or from a plug that isn't making secure contact in
  the outlet - check it.

* Voltage fluctuations.  Occasional flickering when high wattage appliances
  kick in is not unusual especially if they are on the same branch circuit but
  could also be a symptom of other electrical problems like a loose Neutral
  connection - see the section: "Bad Neutral connections and flickering lights or worse".

  If a dimmer control is present, keep in mind that these are somewhat more
  sensitive to slight voltage fluctuations especially when set at low levels.
  You may simply not have noticed any flickering with a normal on/off switch.

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