New Bulb Goes Blooey

Why are your new-technology bulbs failing to work right?

You just spent a lot of money on new-technology lightbulbs. But everything seems to be going wrong. Here is a guide of what to do when you have troubles:

SYMPTOM POSSIBLE CAUSE WHAT TO DO
Electrical shock Defective wiring. Test and repair wiring.

Use of a wrongly manufactured light bulb.

  ELECTRICAL SHOCK HAZARD!  

Use of these imported candelabra-base LED bulbs with enlarged metal ferrules (indicated in diagram) that are connected to the screw shell. An unsuspecting person touching or changing this bulb can contact this live metal part and receive an electrical shock.

Somehow these bulbs have never been tested for safety. They do not meet US government safety standards.

dangerous bulb An unpolarized plug on a Christmas light string or an open neutral wire in a light fixture can leave the ferrule connected to the live side of the power line.

DO NOT USE THIS KIND OF BULB in Christmas light strings or in any other socket where the ferrule is exposed. Touching it can cause an electrical shock.

Lamp will not light No current. Check to see if power is available at outlet.
Lamp at normal end of life. Replace with correct type.
Switch or dimmer not compatible with lamp. Replace switch, dimmer, or lamp with correct type.
Keep one incandescent lamp in fixture or add passive load. *
Lamp can't be used with a dimmer. Remove dimmer and replace with ordinary switch.
Replace lamp with correct type for dimmer.
Special control needs incandescent lamp to work. † Replace with correct type of lamp.
Keep two incandescent lamps in fixture or add passive load. *
Wrong type of lamp used for fixture. Replace lamp with correct type.
Short lamp life Repeated switching uses up compact fluorescents (CFL) life. Don't use CFLs with motion detectors.
Some 100 volt lamps for Japan mistakenly sold in the US. Return to store for exchange with correct replacement.
Attempt to use lamp with incompatible switch, dimmer, or
special control. †
Replace switch or dimmer with the correct type.
Replace lamp with correct type for switch or dimmer.
Some lamps overheat when the screw base is up. Replace with lamp intended for use with the base up.
Many lamps overheat in enclosed fixtures. Replace with lamp intended for use in enclosed fixture.
Lamp life rating based only on LED life. The power supply in the bulb base burns out first.
Lamp rapidly flashes when on Lamp at normal end of life. Replace lamp.
Switch, dimmer, or special control not compatible
with lamp. †
Replace switch, dimmer, or special control with correct type. †
Replace lamp with correct type for existing equipment.
Keep two incandescent lamps in fixture or add passive load. *
Lamp briefly blinks once every
few seconds when off
Leakage current from dimmer RF filter. Replace switch or dimmer with the correct type.
Keep one incandescent lamp in fixture or add passive load. *
Leakage current from neon-lighted switch or switch plate. Replace switch with unlighted switch.
Keep one incandescent lamp in fixture or add passive load. *
Leakage current from special control. † Replace special control with one for new bulbs. †
Keep one incandescent lamp in fixture or add passive load. *
Capacitive leakage from 3-way switch traveler wires. Keep one incandescent lamp in fixture or add passive load. *
SYMPTOM POSSIBLE CAUSE WHAT TO DO
Radio frequency interference
(RFI) when lamp is on
Cheap CFL or LED bulb has no RFI protection. Replace lamp with different brand that emits less RFI.
Add radio-frequency filtering to fixture. ‡
If only owner's receivers affected, move them or their antennas.
Large number of lamps, each emitting legal RFI levels. Replace with bulbs that emit less RFI.
Add RFI shielding or filtering to fixtures. ‡
If only owner's receivers affected, move them or their antennas.
Radio frequency interference
(RFI) when lamp is off
Leakage current activates switching power supply in lamp. Replace lamp with different brand.
Add radio-frequency filtering to fixture. ‡
Keep one incandescent lamp in fixture or add passive load. *
See "Lamp blinks briefly every few seconds when off" above.
Carrier current interference
when lamp is on
Lamp sends interference onto power lines. Try replacing lamp with different brand.
Add choke-input radio-frequency filtering to fixture. ‡
Lamp RFI filter loads down carrier current signal. Add choke-input radio-frequency filtering to fixture. ‡
Reduced light from lamp Difference between old lamp and new. Try replacing lamp with same brand and model.
Lamp near end of life. Replace lamp.
Lamp affected by temperature extremes. Replace lamp with outdoor type.
Lamp damaged by long-term direct sunlight. Protect lamp from sunlight.
Lamp light changes color Difference between old lamp and new. Try replacing lamp with same brand and model.
Lamp at end of life. Replace lamp.
Lamp damaged by long-term direct sunlight. Protect lamp from sunlight.
Lamp emits awful stink Fusible resistor in switching supply burned out. Replace lamp (has ended its life to prevent a fire).
Short lamp life outdoors Lamp not rated for outdoor use. Replace lamp with correct type.
Insects building nests in cooling fins or slots. Choose a lamp with no cooling fins or slots.
Protect lamp with screening or enclosure.
SYMPTOM POSSIBLE CAUSE WHAT TO DO
Lamps cause low power
factor
Lamps not rated for industrial/business use. Replace lamp with power-factor correcting type.
Use isolation transformer for lamps, correcting on load side.
RFI filter changes power factor. Redesign RFI filter to prevent phase shift.
Lamps emit power-line
harmonics
Lamps not rated for industrial/business use. Replace lamp with low-harmonic type.
Use tuned isolation transformer to power lamps.
Ends of CFL tube turn black Lamp near normal end of life. Replace lamp when it fails.
Small black spots on CFL tube Mercury condensation on inside of tube. This is normal. It won't affect performance.
CFL dim when first turned on This is part of the design of some lamps to increase life. This won't otherwise affect performance.
Colors wrong in photographs
Taken under CFL lamps
Bright lines in spectrum change some colors. Use a different light source.
Gaps between the bright lines leave out certain colors. Use a different light source.
Color balance does not match bulb color temperature. Use a different color temperature bulb.
Invisible ultraviolet emissions record as blue in image. Use a different light source.
Ultraviolet emissions cause some colors to fluoresce. Use a different light source.
Colors wrong in photographs
Taken under LED lamps
Gaps in the spectrum leave out some colors. Use a different light source.
Slopes in the response curves shift recorded colors. Use a different light source.
Color balance does not match bulb color temperature. Use a different color temperature bulb.
Invisible ultraviolet emissions record as blue in image. Use a different light source.
Ultraviolet emissions cause some colors to fluoresce. Use a different light source.
The light of a clear bulb
is a garish orange
The color temperature is too low. Choose a bulb with a higher color temperature.
Manufacturers are wrongly favoring this "soft white" color. Write to manufacturers to complain.
The bulb does not work
in a device requiring
an incandescent bulb
The lamp does not give off the required heat. Use a real incandescent or halogen bulb.
The lamp does not have the resistance curve needed by
the equipment.
Experiment to find a lamp with the required curve. #
Write to manufacturers to complain.
The lamp is not the resistive load the device needs. Experiment to find a lamp with a resistive load. #
Write to manufacturers to complain.
SYMPTOM POSSIBLE CAUSE WHAT TO DO
The Special Control Device
sticks in the ON Position
The lamp shifts the current phase, welding relay contacts
(tapping on motion sensor head unsticks contacts).
Use a real incandescent or halogen bulb.
Keep two incandescent lamps in fixture or add passive load. *
Phase shift in the lamp power supply locks the phase
control device on
(removing power from Special Control Device turns it off).
Use a real incandescent or halogen bulb.
Try a different brand of lamp.
Keep two incandescent lamps in fixture or add passive load. *
The Special Control Device
forgets its programming
The lamp power supply causes a surge that erases
the programming.
Try a different brand of bulb.
Add radio-frequency filter to device output. ‡
Use a real incandescent or halogen bulb.
Keep two incandescent lamps in fixture or add passive load. *
Power line surge erases the programming. Add choke-input radio-frequency filter to device input. ‡
Keep two incandescent lamps in fixture or add passive load. *
Power line surge or sag causes the bulb to emit a surge
that erases the programming.
Try a different brand of bulb.
Add radio-frequency filters to both input and output. ‡
Use a real incandescent or halogen bulb.
Keep two incandescent lamps in fixture or add passive load. *
SYMPTOM POSSIBLE CAUSE WHAT TO DO


LED passive load * Adding a Passive Load:

Adding a passive resistive load can make a switching or dimming device work if it otherwise malfunctions when used with new-technology lamps. There are several ways to make a passive load.

In the diagram at right, the passive load should use the TYPE A circuit. The TYPE B circuit is for light strings or fixtures with multiple half-wave series (not covered here).

A much smaller load can be added if the only problem is a lamp blinking when it is turned off. Usually 10 watts or less is sufficient.

† About Special Control Devices:

What is different about Special Control Devices:

Special Control Devices alter the AC power fed to the lamp in various ways. Incandescent and halogen lamps respond to this by changing brightness. But the new-technology lamps can malfunction when fed power from Special Control Devices.

Various Special Control Devices make the following changes to AC power:

A tool to test special device outputs and LED lights for load and polarity:

This testing circuit from my Christmas light tester page can do this.

Note that, for this purpose, a bulb is said to be malfunctioning if it blinks on and off, flickers, is dim, gets hot, keeps changing brightness, or goes out after a short time. This can damage the bulb, so shut it off quickly if this happens.

LED string tester This tester can test all of the following:

Features of the Tester:

Information about the tester circuit:

Other problems with Special Control Devices:

‡ Radio Frequency Interference Filter

power line filters
Method
Used
Components Cutoff
Freq
60 Hz Impedance
SeriesShuntSeriesShunt
20 Ft 16 ga Cord0.16 Ω0.5 μF 2.0 MHz0.16 Ω5.3 KΩ
20 Ft 16 ga Cord0.16 Ω1.0 μF 1.0 MHz0.16 Ω2.7 KΩ
Ferrite Filter1 μH0.5 μF 225 KHz0.000377 Ω5.3 KΩ
Ferrite Filter1 μH1.0 μF 159 KHz0.000377 Ω2.7 KΩ
RFC **0.1 mH0.5 μF 22.5 KHz0.0754 Ω ♥5.3 KΩ
RFC **0.1 mH1.0 μF 15.9 KHz0.0754 Ω ♥2.7 KΩ
Choke ***1 mH0.5 μF 7.1 KHz0.754 Ω ♥5.3 KΩ
Choke ***1 mH1.0 μF 5.0 KHz0.754 Ω ♥2.7 KΩ

** RFC = Radio Frequency Choke.
*** Choke is on same schematic location as RFC.
♥ This is double the calculated impedance, because there are two chokes.
The wire gage in the chokes must be able to carry the current of the lamps.

If a new-technology lamp creates radio frequency interference (RFI), the interference must be removed. Here are several cases of RF emission and ways to cure them:

  1. RF radiated into the air from the bulb:
  2. RF radiated into the air from the power lines feeding the bulb:
  3. RF from the bulb entering the power lines and interfering with carrier current signals:
  4. The bulb when off is interfering with X-10 or carrier current signals:

The designs with the chokes are better filters. But the others use parts that are more readily available.

Test these circuits with the intended load before installing it. Some of the new-technology bulbs might have trouble with these circuits too.

More Rules For Making A Filter:

# Finding the Resistive Curve of an Incandescent or Halogen Lamp

Incandescent lamps increase their resistance when the filaments become hot. This is how to find how an individual lamp type behaves.

lamp curve finder The simplest procedure to find the curve is:

  1. Get at least 2 identical bulbs of the lamp type to be tested.
  2. Find the cold resistance by measuring the resistance with an ohmmeter.
  3. Use the circuit at right to find the hot characteristics of the lamp.
  4. Install two of the identical bulbs in sockets 1 and 2.
  5. Turn switches A and B on to read hot values at full voltage (120 V).
  6. Turn switch B off to read the hot values at half voltage (60 V).
    Note that a wattmeter reads the combined power of both bulbs, so divide this one wattmeter reading by 2 before entering it. Do not change an ammeter reading.
  7. Enter the values in a table like the one below. Excel can be used.
  8. Calculate the remaining columns using the formulas below:
  9. Plot the results on a chart (example below right).

lamp curve chart Lamp Resistance Curve Formulas:

Lamp Resistance Curve Chart:

Values# of
Lamps
Voltage
/ Lamp
Power
/ Lamp
Current
/ Lamp
Resistance
/ Lamp
Total
Power
Case# VoltsWattsAmpsOhmsWatts
Cold 000140
Eighth 81540.275632
Quarter 430100.339040
Half 260290.4712458
Full 11201000.83144100

If desired, more points on the curve can be obtained by connecting even more identical lamps in series. If this is done, remember to divide any wattmeter readings by the number of bulbs in series.

Use the resistance curve charts to compare possible replacement lamps with the original lamp.

Factors affecting the actual life of a new technology bulb

  1. Starts/DayLife DaysLife Years
    1650017.8
    232508.9
    321675.9
    416254.4
    513003.6
    106501.8
    20 ♠3250.89
    50 ♠1300.36
    20/year ♥118706325
    A fluorescent tube has a limited number of starts, but no limit on run time.

    A CFL has a life of about 6500 starts.

    Here is a table of expected lifetimes. This is limited to the tube itself, not the electronics.

    ♠ CFL used in a motion detector

    ♥ CFL never turned off except during a power failure

  2. The power supply of a CFL or LED lamp has a finite lifetime

    If the lamp is not used frequently, the electrolytic capacitors fail.

    If the lamp is left on, the electronics heat up and fail earlier.

  3. The power supply of a CFL or LED lamp can fail without cooling air

    If the lamp is not rated for enclosed use, enclosing it shortens its life.

    Bugs building nests in cooling slots shortens the life of the lamp.

  4. The power supply of a CFL or LED lamp can fail in the wrong orientation

    If the lamp is not rated for base up use, using it with the screw shell pointing up shortens its life.

    If the cooling slots are pointing down, heat can't escape from the power supply.



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