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Luminous tube trouble shooting

 
PROBLEM: TUBE FLICKER, "BLINKING"

THE ELECTRIC SIGN AS A SYSTEM OF COMPONENTS

SYSTEM COMPONENT:
POSSIBLE CAUSE :
TEST :
POSSIBLE SOLUTION :
Supply Voltage
Low line voltage can result in low transformer output voltage.
Measure input voltage at transformer with a multimeter.
1) Reduce the load on the line voltage supply transformer.
2) Install buck-boost transformer.

SYSTEM COMPONENT:
POSSIBLE CAUSE :
TEST :
POSSIBLE SOLUTION :
Supply Wiring and Connections
Loose connections.
Visual inspection, manual check at connection points.
Secure connections.

SYSTEM COMPONENT:
POSSIBLE CAUSE :
TEST :

POSSIBLE SOLUTION :
Transformer
Breakdown of secondary winding. (Usually induced by another fault condition.)
Disconnect GTO (Gas Tube Only) wire at transformer. Measure output voltage at transformer with multimeter using a hi-voltage probe and/or replace transformer.
Replace transformer and continue inspection for root cause of failure.

SYSTEM COMPONENT:
POSSIBLE CAUSE :



TEST :




POSSIBLE SOLUTION :
Secondary Wiring & Connections
a) Poor wiring connection or poor connection between luminous tubes.
b) Secondary wiring breakdown
c) Capacitive coupling of secondary wiring to ground. (Caused by
excessive lengths of GTO wire in close proximity to grounded metal.)
a) Visual inspection, manual check at connections.
b) No great test. Disconnect GTO wire at tubing start/finish and
insulate: measure output current from transformer to GTO (no tube load):
output current indicates and insulation breakdown or capacitive coupling
leakage.
a) Secure connections.
b) Replace GTO wiring.
c) Reduce the length of HV GTO run by rewiring for mid-point ground
connection, replace GTO conduit with non-metallic conduit; add insulation sleeving to GTO wire.

SYSTEM COMPONENT:
POSSIBLE CAUSE :

TEST :


POSSIBLE SOLUTION :
Luminous Tube
a) Defective tube section.
b) Excessive tube footage.
a) Verify tube integrity with glow coil tester.
b) Reduce tubing load by one section. Test circuit loading (%I.S.C -
percent short circuit load test)
a) Replace defective tube section.
b) Replace transformer with next higher OCV rating.

SYSTEM COMPONENT:
POSSIBLE CAUSE :


TEST :



POSSIBLE SOLUTION :
Installation & Environment
a) Water.
b) HV (High Voltage) spacing to ground.
c) Cold ambient temperature.
a) Perform visual inspection for evidence of previous presence of water
build-up near the transformer and around GTO wire runs. Check for
signs of arcing.
b) Visual inspection for signs of arcing.
a) Improve physical installation as required to eliminate water intrusion.
b) Insulate any bare connections. Correct any reduced spacing
problems.
CAUTION: Servicing of electric signs should only be performed by qualified personnel. Disconnect power before servicing. Observe OSHA guidelines for safe electrical practices.
 
PROBLEM: SIGN OUTAGE

THE ELECTRIC SIGN AS A SYSTEM OF COMPONENTS

SYSTEM COMPONENT:
POSSIBLE CAUSE :

TEST :
POSSIBLE SOLUTION :
Supply Voltage
Low line voltage. Severe undervoltage can result in transformer OCV
below tube arc volt requirement.
Measure input voltage at transformer with a multimeter.
1) Reduce the load on the line voltage supply transformer.
2) Install buck-boost transformer.

SYSTEM COMPONENT:
POSSIBLE CAUSE :

TEST :


POSSIBLE SOLUTION :
Supply Wiring & Connections
a) Broken wire/connection.
b) Shorted wire.
a) Measure input voltage at transformer with multimeter.
b) Typically causes immediate trip of circuit breaker. May be verifiable
with ohmmeter.
a) Secure connections. Repair any supply line breaks.
b) Repair wiring short.

SYSTEM COMPONENT:
POSSIBLE CAUSE :

TEST :


POSSIBLE SOLUTION :
Transformer
a) Breakdown of secondary winding. (Usually induced by another fault condition.)
b) Primary winding short-circuit.
a) Disconnect GTO at transformer. Measure output voltage at transformer with multimeter using a hi-voltage probe and/or replace transformer.
b) Typically causes immediate trip of circuit breaker.
a) Replace transformer and continue inspection for the root cause of failure.
b) Replace transformer. Continue inspection for the foot cause of the failure. Verify the transformer rating agrees with voltage supplied.

SYSTEM COMPONENT:
POSSIBLE CAUSE :



TEST :



POSSIBLE SOLUTION :
Secondary Wiring & Connections
a) Poor wiring connection or poor connection between luminous tubes.
b) Secondary wiring breakdown.
c) Capacitive coupling of secondary wiring to ground. (Caused by excessive lengths of GTO wire in close proximity to grounded metal.)
a) Visual inspection, manual check at connections.
b) No great test. Disconnect GTO wire at tubing start/finish and insulate: measure output current from transformer to GTO (no tube load): output current indicates and insulation breakdown or capacitive coupling leakage.
a) Secure connections.
b) Replace GTO wiring.
c) Reduce the length of HV GTO run by rewiring for mid-point ground connection, replace GTO conduit with non-metallic conduit; add insulation sleeving to GTO wire.

SYSTEM COMPONENT:
POSSIBLE CAUSE :

TEST :


POSSIBLE SOLUTION :
Luminous Tube
a) Defective tube section.
b) Excessive tube footage.
a) Verify tube integrity with glow coil tester.
b) Reduce tubing load by one section. Test circuit loading. (%I.S.C -percent short circuit load test)
a) Replace defective tube section.
b) Replace transformer with next higher OCV rating.

SYSTEM COMPONENT:
POSSIBLE CAUSE :



TEST :




POSSIBLE SOLUTION :
Installation & Environment
a) Water.
b) HV (High Voltage) spacing to ground.
c) Cold ambient temperature.
d) Overheating.
a) Perform visual inspection for evidence of previous presence of water build-up near the transformer and around GTO wire runs. Check for signs of arcing.
b) Visual inspection for signs of arcing.
c) Can occur in ambients below 40ºF.
d) Visual inspection.
a) Improve physical installation as required to eliminate water intrusion.
b) Insulate any bare connections. Correct any reduced spacing problems.
c) Reduce footage per transformer when using Hg filled tubing.
d) Insure transformer has opportunity for heat transfer to minimize heat build-up.
CAUTION: Servicing of electric signs should only be performed by qualified personnel. Disconnect power before servicing. Observe OSHA guidelines for safe electrical practices.

ADDITIONAL NOTES ON LUMINOUS TUBE TRANSFORMERS
• Use tubing chart to select proper transformer, then fine tune application with six step (%I.S.C.) loading procedure.
• The most typical tubing size used is between 12- and 15-milliameters. 25-milliameter tube is typically used in cold cathode lighting.
• When evaluating tube resistance, each pair of electrodes represent about one additional foot of tubing.
• Beer signs typically use 20- or 30-mA transformers and 12- to 15-mm tubing.
• Tubing is sometimes referred to as "stick."
• Gasses used are neon and argon with mercury (referred to as mercury).
• Pure neon burns red in clear tubing. It will turn orange if air gets in the tube.
• In mercury tubing you can get dark spots due to mercury migration, especially when using electronic transformers which have a dc offset bias at the transformer output.
• Overloaded electrodes cause the common problem of cracked tubing.
• Bad bends (smaller diameter at the bend) will cause higher resistance that lead to overloading and hard starting.
• To measure tube current you must use an analog mA meter. The high voltage will destroy a digital meter. The meter should be purchased from a luminous transformer distributor. A qualified Sign & Neon Technician should perform the tests.
• A "HOT" transformer is typically overheated by excessive capacitive leakage current between the GTO cable and the conduit used on long runs.
• If the transformer has a "ground lug" it must be a MPG transformer.
• Open Core & Coil transformers can only be used INDOORS. Condensation outdoors will quickly cause them to short out due to the high voltage.
• UL 48 for signs require that luminous tube transformers must have an enclosure if they are Core & Coil. Most signs are not UL Listed.
• GTO stands for "Gas Tube Only." It has insulation designed to withstand the high open circuit voltages present with luminous tube transformers.
• GTO wire comes as GTO-10 and GTO-15. GTO-10 is for 10,000-volt and below applications. GTO-15 is used for 10,000- to 15,000-volt applications.
• If GTO wire has been nicked or cut and has arced in the conduit you will see a white powder residue when it is pulled out.
• The term "tubulation" is a slang term used to indicate luminous tube that has already been bent for an application.
• Luminous tube transformers with secondary fault protection do no operate well when dimmed of flashed.
• Universal Lighting TriFormers™ and Isolated Secondary design luminous tube transformers may be dimmed or flashed.


ADDITIONAL QUESTIONS ON NEON

Where do the different colors in luminous tubing come from?
The initial color source for luminous tubing is an inert gas, which emits a characteristic color when electricity is applied. The two most common gases are neon and argon/mercury. Pure neon emits a fiery red color, while the argon/mercury emits a subdued blue color. A variety of fluorescent powders (phosphors) may be painted or baked to the inside walls of the tubing to produce different colors and shadings such as pink, turquoise and green in cool to warm shades.

Luminous tubing is also available in colored glass such as deep clear reds, blues and greens. The lavishly saturated colors produced in this type of tubing are sometimes referred to as "exotic" or "Euro" glass. The quality and color of the light may be altered with the addition of fluorescent phosphors to the colored glass.

How does a luminous tube produce light?
Electric current bombards the inert gas atoms with electrons knocking other electrons out of orbit. The electrons collide with other free electrons sending them back toward the atoms. As free electrons are absorbed back into the atoms, energy is released in the form of light.

How do you bend luminous glass tubing?
Generally when bending luminous tubing four gas burners are used. The burners use a gas and air mixture to raise the flame temperature. The glass tubing is rotated and rocked in the burner flames to affect the bends. Crossfire and fishtail burners are used to produce most angled bends and splices. Ribbon burners are used to produce curves and sweeps. Hand held torches are usually used for splices or tapering or tipping off electrodes.

How is the gas put into the tube?
Luminous tubes are capped off by two glass electrodes which have wire passing from outside to inside. The tubing is sealed to the pumping system or manifold. The manifold has glass stopcocks or valves that allow sections to be selectively opened or closed.

A very high vacuum pump draws the air out of the tube while a high voltage-high amperage transformer bombards and heats the remaining air to produce temperatures in excess of 500º F. This allows the tube to achieve a higher degree of purity. When a very high vacuum is reached and the tube begins to cool, a small amount of inert gas is introduced from a flask or tank. The tubing is then heated and as it is pulled it the glass tube is drawn in and creates an airtight seal.

Are the gasses in luminous tubing dangerous?
Neon and argon are inert gasses and pose no personal or environmental threat by themselves. Argon/Mercury filled tubing contains a small amount of mercury, which poses no danger as long as the tubing is in tact. EPA approved disposal methods must be followed for disposal of argon/mercury filled tubing. Check with your local Environmental Protection Agency offices for instructions on proper disposal of tubing containing mercury.

Is luminous tubing bent freehand or with a pattern?
Both. In artistic work the tube may be bent freehand or with a pattern. In commercial applications such as signs, channel letters, etc., the glass is usually bent over a fire resistant pattern.

Can luminous tubing be repaired?
Yes, luminous tubing can be repaired and/or recharged.

How long will a luminous tube sign last?
Many factors play into the life span of luminous tube including the environment in which it is placed, the quality of the power feeding the transformer, quality of installation, and acts of God (lightning, storms, etc.). Luminous tube may last decades in the perfect environment, but in sensible terms most luminous tube signage should last from eight- to fifteen-years.
 

                    

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