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Technical Service FAQs 


This page provides answers to basic questions pertaining to maintenance and repair of UV systems and equipment manufactured by Heraeus Noblelight America LLC.  Just click on any of the topics listed below for quick information. 


This list is continually updated.  If you don’t see the question/answer you are looking for, please contact us 

Cooling Air: Blower Sizing and Ducting 

Heat Management
Service Contracts 

Lamp Unit Maintenance 

Electrodeless bulb and reflector cleaning
Bulb Identification / Replacement Bulbs

Telling if a bulb is good or bad
Calibrating Variable Power Supplies

Testing and Troubleshooting Power Supplies
RF Faults
RF Mounting 

Cable Care
Maintenance Log 

Changing Electrical Operating Frequency  



Cooling Air: Blower Sizing and Ducting 


Q. Why do UV curing systems need cooling air? Can I simply follow common HVAC blower and ducting design practices?
All UV curing lamp systems require some type of cooling to ensure proper operation. A Heraeus Noblelight irradiator requires a certain amount of air to maintain the magnetron and bulb surface temperatures at optimal performance. While the blowers and ductwork may look like typical heating and air conditioning blowers and ducting, the requirements are very different because the volumes and velocities are much higher in a UV system. As a result, it is very important when installing a new system, or making any significant changes such as moving blowers or changing the number of lamp units operating, to alert whoever is specifying or installing the blowers and ductwork that the design requirements are very different than what they are probably used to.


Heraeus Noblelight typically recommends blower sizes based on the number and type of UV systems installed and an assumption about blower location and length of duct run. Sometimes problems are encountered because the blower is placed much further away, or the duct size or routing is very different than that assumed originally. These problems can easily be avoided by paying attention to what was originally assumed, and to the air requirement specifications for the lamp systems. If a blower must be placed farther away than originally planned, then it may need to be a larger size. Heraeus Noblelight America’s technical service and applications engineers can provide guidance. If you are installing a system or just plan to make changes, contact us first to make sure blower sizes and duct runs look adequate. 

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Heat Management 


Q. How can I reduce the heat from the UV lamp? It is damaging my substrate.
A. A UV lamp system not only produces UV light, it also produces infrared radiation (IR). In some applications, excess heat can damage sensitive parts, cause wrinkling on printed films, adhesion failures, etc. In other applications, heat can be beneficial by improving the 'flow' of the UV curable ink, coating or adhesive onto the substrate surface and in others by improving the cross-linking of chemistries.


The main source of IR is the quartz bulb. As the bulb gets hot, it emits IR energy. The amount of IR emitted from a bulb is primarily a factor of its surface area. A larger bulb diameter means a larger surface area – and therefore higher IR emissions. Conversely, a smaller diameter bulb has less surface area, therefore lower IR emissions. 


This is one key advantage Heraeus Noblelight’s small diameter bulbs have over typical electrode type bulbs. Below are some suggested ways to reduce heat which may be damaging your substrate. 


Cooling: We recommend that you remove 30% more air than is supplied to the lamp units so that a negative air pressure exists under the lamps. Light shielding louvers are also recommended to allow for a free flow of makeup air. As the makeup air is pulled through the light shield, it removes ozone and chemistry odors as well as heat from the substrate. 


Speed: The amount of heat that the substrate sees is also a function of how long it is being exposed. In some cases, it is possible to increase the speed on the production line and still maintain a good cure, while reducing the amount of heat at the substrate. 


Reflectors: The standard aluminum reflector not only does an excellent job of reflecting and focusing UV, but also the IR. Another option to consider is a dichroic reflector. Dichroic reflectors have 50 or more layers of a dielectric coating applied to their surface. This coating allows UV light to be reflected, but absorbs much of the longer IR wavelengths. The heat is then dissipated from the reflector surface by air-cooling. 



Dichroic Reflector 
A dichroic reflector is shown on the left next to a standard reflector on the right. 


Reflector Chart
If one of these methods alone does not yield the desired results, a combination can be very effective!


More detailed papers are available: 


Heat Management: From Source to Substrate   


Dichroic Reflectors Applied to High Peak Irradiance Microwave Powered UV Lamps  


Temperature Measurements Under UV Lamps 


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Service Contracts 


Q. What happens if a system goes down shortly after the contract service has been completed?
Heraeus Noblelight America will handle this just as we would a normal service call follow up. We first determine the problem and the solution by working with the customer over the telephone, as this may be the fastest method of getting the system back up and running. If we cannot resolve the issue quickly, or if the customer prefers, we will send a technician to the customer site at no charge (or for "Return to Base" contracts we have the systems sent to Heraeus Noblelight America at no charge). If we find that the cause was something we should have found during our inspection/service, we will add another cycle to the service contract at no charge to the customer. If customer negligence is the cause, then fees will need to be charged for these services. 


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Q. How quickly does Fusion UV respond to failures after service?
We guarantee response within 48 hours.


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Q. Is there a warranty that comes with the service contract?
The Gold level contract carries a complete system warranty – same as new – for as long as the equipment is under contract. The Bronze and Silver levels are primarily inspection contracts; therefore, the warranty will be limited to the contract specifics.  However, if we missed something during service, we will make it right!


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Lamp Unit Maintenance 


Q. How do I verify proper air pressure in the lamp unit?
A. An important part of any maintenance plan should include periodic verification of the air pressure in the lamp unit to ensure maximum life from bulbs and magnetrons. To test the pressure in the lamp unit, remove a screw from the face of the lamp (fig.1), insert the probe from a differential pressure gauge (fig.2) and measure the internal air pressure. Compare this reading to the minimum specification for your specific model lamp system.

Model I601 Shown
Lamp Unit Maintenance
Fig. 1

Lamp Unit Maintenance - air pressure
Fig. 2 

Filtered cooling air from a blower is fed into the lamp unit, passes through the magnetrons, and over the bulb through two microwave slots and a series of small cooling holes in the reflector. The air then passes out of the lamp cavity through the RF screen and is exhausted. In addition to cooling the magnetrons and bulb, this flow of air helps keep the bulb and reflector clean, which extends the time needed between maintenance cycles. 



For more detailed specifications and instructions, please consult the Installation, Operation and Maintenance Manual for your Heraeus Noblelight, or contact our Technical Service Department. 


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Electrodeless Bulb and Reflector Cleaning 


Q. How should I clean my electrodeless bulb and reflector?
Bulbs and reflectors should be inspected for external contamination every 500 hours of operation (the photo shows an obviously very contaminated surface). If you consistently find deposits on the bulb and reflector during inspection, consider changing the air filters more frequently. If the bulb or reflector surfaces show signs of dullness, dirt, oil or other contaminants, they should be removed and cleaned as soon as possible to prevent any permanent damage.


Contaminated Bulbs  

To clean the bulb and reflector, use a lint-free cloth and a cleaner that uses no waxes, silicones, dyes or perfumes such as Windex® or Simple Green®. Isopropyl alcohol or methanol can be used where solvents are allowed. In extreme cases of bulb contamination, a cleaner with mild abrasives such as Soft Scrub® can be used, but it is extremely important to thoroughly rinse the residue from the bulb before re-installing it in your lamp system. Cleaners with abrasives should not be used on reflectors. 




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Q. How can I determine what type of UV bulb I have?  How do I know what replacement bulb to order?
A. When installing a replacement bulb it is imperative to make sure you have the correct part. Check the part number of the bulb being removed and verify that the replacement bulb has the same part number.

The figure below shows how to identify your Heraeus Noblelight bulb. Note especially the six-digit part number followed by a letter designation. When ordering replacements, only the part number is required. The most common Heraeus Noblelight America bulb types are H, H+, D and V. Each of these bulb types has a different spectral output that is matched to your chemistry and application. The bulb shows here is an H bulb. 


Identify buld 



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Q. After removing the reflector for inspection and/or cleaning and I'm ready to reinstall the reflector, what should I do with the RF gaskets?
Anytime you install a reflector, whether it's a new one or the old one, we recommend you install new RF gaskets. Never install the reflector without the RF gaskets - they are very important for proper operation and reliability of the lamp unit.


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Q. Why and how do I replace the RF gaskets when I remove or replace the reflector?
The RF gaskets maintain proper electrical contact for the reflector, which actually forms the RF cavity for the microwaves energizing the UV bulb. Without proper RF gasket installation, component life and reliability of the lamp will be reduced.



Replace RF Gasket
 Fig. 1 

Before installing new RF gaskets, lay them flat on a hard work surface and lightly tap them with the end of a screwdriver (Fig. 1). This will make the RF gaskets easier to install into the waveguide slots.




When installing end reflectors or new RF gaskets, it is important to position the end reflector into the waveguide first, then install the RF gasket between the end reflector and the waveguide slot.

Installing end reflector 
Fig. 2 

The reflector will expand and contract with the constant heating and cooling of the lamp unit, which can cause the reflector screws to loosen slightly over time. To minimize this, we recommend that you run the lamp unit for at least 20 minutes; shut it off; let it cool down; remove the RF screen, and then retighten the reflector screws through the holes provided in the RF screen frame. You may only get another turn, but this small step can greatly increase the component life and reliability of your lamp unit. 


In many applications, a small investment in better air filtration will pay off well in reduced maintenance costs and less time spent cleaning bulbs and reflectors. 

For more information please consult your Installation, Operation and Maintenance Manual or contact your local Heraeus Noblelight Technical Service Office. 



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Telling if a Bulb is Good or Bad 

Q. How do I know if a UV bulb is good or bad?
There are a few simple and inexpensive methods to determine whether a bulb is good or bad.

Method 1: Some Heraeus Noblelight power supplies are equipped with "Photocell Test Points" that make checking the bulb very easy. Simply put your voltage meter on these test points while the system is in "Standby"; if the voltage reading drops when the system is turned "On", then the bulb is most likely good. Refer to your Installation, Operation and Maintenance Manual for more information on photocell test points. 


Photocell Test Points
Method 2: On systems that do not have test points, you can observe the system using view ports for safe observation to see if the bulb lights up when the system is turned "On". If it does, a general rule of thumb is that the bulb is "good". 


Test bulbs
Method 3: To test bulbs that have been removed from a lamp unit, use a high-frequency generator. Place the bulb on a bench-top and touch the generator probe to the bulb. If the bulb lights up as shown in the picture below, it is a good bulb. This method ionizes the gases at a very low level and generates an insignificant amount of UV.  Nevertheless, we recommend wearing UV-rated safety glasses. 


High Frequency Generator
For more information on high frequency generators or bulb testing in general, please contact us at 301-527-2660 x8500 or 



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Calibrating Variable Power Supplies


Q. Is it necessary to calibrate Variable Power Supplies (VPS)?
A. Variable Power Supplies (VPS) do not require routine calibration. Every VPS manufactured and shipped from Fusion UV is calibrated as part of our normal testing procedure. However, you should recalibrate if you have replaced the high voltage board, a high voltage diode, control transformer, or have swapped or replaced one of the magnetron boards. If the unit is in need of calibration, it will display a "No Calibration" message. This recalibration is important for two reasons. First, it ensures maximum useful life of the magnetrons and secondly, it assures the operator that the power level selected will be accurate to within 2%. In other words, 100% is 100%!



For more detailed information or to obtain a step-by-step guide on how to calibrate your VPS, please contact us at 


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Testing and Troubleshooting Power Supplies


Q. What tools are necessary to test and troubleshoot power supplies?
A. To accurately test and troubleshoot a Heraeus Noblelight power supply, you need a volt-ohm meter. Since there are three different types of volt-ohm meters, be sure to select the proper type for accurate measurements. Below is a brief discussion of each and their proper use.

  • "Standard" Digital Volt-Ohm Meter (DVM) – this is the most common digital meter. It provides accurate measurements of resistance, DC voltages and currents, and sinusoidal AC voltages and currents. 
  • "True RMS" Digital Volt-Ohm Meter – a True RMS (Root Mean Square) meter also provides accurate measurements of resistance and DC voltages. It differs from the "standard" DVM in its ability to provide true RMS measurements of non-sinusoidal AC voltages and currents. 
  • Analog Volt-Ohm Meter (VOM) – This instrument uses an indicating needle which swings across a calibrated scale. It measures resistance, DC voltages and currents, and AC voltages and currents. It is usually powered by a 6.0V (minimum) battery. 



Any of these meters can be used to measure the three-phase, single-phase AC input power or DC voltages such as the photocell test points or control card diagnostics on your Fusion UV power supplies.  However, only a True RMS meter should be used to measure the filament voltage because the waveform is not sinusoidal. A standard DVM will only produce a misleading voltage reading when trying to measure anything other than a DC signal or a sine wave. The filament voltage reading can differ by as much as 20 volts. A properly set filament voltage will ensure maximum lifetime out of your magnetrons, so it is important to measure and set it accurately. 



To measure magnetron currents a digital meter is required for accuracy. 



To diagnose capacitors and diodes, an analog meter should be used. In both cases, a meter with a minimum 6.0V battery is required to ensure accurate readings. 



For more detailed information consult your Installation, Operation and Maintenance Manual or contact us at 


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Q. What routine/preventive maintenance does Heraeus Noblelight recommend for power supplies?
A. Though power supplies are often overlooked when it comes to preventive maintenance, there are a few steps that should be taken to make sure your power supply continues to operate trouble free and at maximum efficiency.



The frequency of maintenance will depend on your operating environment. Start by inspecting your power supply every three months. If you find that the power supply always appears to be clean and in good condition or is excessively dirty, then change your schedule accordingly and perform the following preventive maintenance tasks: 


(Before opening and servicing any power supply, first turn off and disconnect all power!) 


  • Clean excessive dust and debris from the interior of the power supply, the fan grills and the rear exhaust screen using clean compressed air. Excessive dust and debris can limit cooling efficiency and encourage arcing across high voltage components. 

Clean excessive dust and debris 

  • Check the connectors on the high voltage transformers, high voltage capacitors, control transformer and high voltage diode modules. The connections must be secure to provide good electrical contact. Loose connections can be repaired by gently squeezing with pliers. Damaged connectors should be replaced immediately. 

Mounting hardware 


  • Check the mounting hardware securing the transformers, diode modules, contactors and control cards. Connections should be firm to ensure the best electrical contact. Loose connections can encourage arcing and erratic operation. 



  • For multiple systems, and where applicable, ensure that all power supplies have the same version software. In some cases, there may be conflicts if different versions of software are being used. 


  • Once the power supply is ready to put back into operation and power has been reconnected, verify that the cooling fans are rotating and working properly, and that there is sufficient clearance at the rear of the power supply for exhaust air to escape. 

For more detailed information, consult your Installation, Operation and Maintenance Manual or contact us at 


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RF Faults


Q. Why is the power supply showing an RF fault, and how do I fix it?
A. Every Heraeus Noblelight lamp system includes an RF detector that shuts the system down if excessive amounts of RF energy are present. Heraeus Noblelight equipment is interlocked to shut down if microwave leakage in excess of 5mW/cm is detected. Our model RF-1 detector automatically tests the components of its circuitry at start-up. For a manual check, hold down the test button on the detector case for approximately 5 seconds.


At start-up, the power supply fault detection circuitry searches the system for a functioning RF detector. A multi-unit UV curing installation must have at least one RF detector per row connected to the master power supply. Additional detectors can be connected to slave units if necessary or if desired. 


The most common causes of an RF fault are: 

  • Torn or damaged RF screen 
  • Failed UV bulb 
  • Defective RF-1 detector 
  • Defective RF Cable 
  • Defective control card 

If you are faced with an RF fault from Standby to Lamp On, there are a few simple things you can do to quickly isolate the cause of the problem: 


1. Check the RF screen for damage, and replace if necessary.  The RF screen helps contain RF energy in the lamp cavity. A damaged RF screen may allow more RF to pass through than is normal. As a result, the RF detector senses the leak and shuts the system down. 


2. With the system turned off, remove the RF detector from its mounting bracket while still leaving it connected to the RF cable and the power supply. Move it at least 10 feet away from the lamp unit and switch the system to ‘On.’ If the unit no longer shuts down with an RF fault, but is now failing with a Lamp Out fault, then the UV bulb has failed to ignite and should be replaced. 


From several feet away, the RF detector cannot detect a true RF leak. So if the system continues to shut down with an RF fault, the problem is not going to be found in the lamp unit. 


The RF fault is the fastest reacting fault circuitry in the system. If a bulb fails to ignite and therefore fails to absorb the RF energy, there will be excessive amounts of RF passing through the screen, which the detector senses and shuts the system down. Once you remove the RF detector, the lamp photocell circuit senses that the light has not come up to power and shuts the system down with a Lamp Out fault. 


3. Once you have ruled out anything in the lamp unit, it is time to look at the RF detector itself, or the RF cable that attaches it to the power supply. If you have a spare RF detector or RF cable, swap them out one at a time to see if either resolves the problem.  If you do not have these spare parts, but have other systems in your plant, then you can use parts from them as test units to determine which part is defective. 


4. If the RF detector and cable appear to be working properly, then the next likely cause is the control card in the power supply.  If you do not have a spare control card but have other systems, you can use a known good control card from another power supply to determine if this is the problem. 

For more information or assistance, please contact us at 


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RF Mounting


Q. What is the purpose of the RF detector, and where should it be mounted?
All Heraeus Noblelight America UV lamp systems include a RF detector to shut the lamp system down if microwave energy in excess of permissible levels is detected. This is usually caused by damage to the lamp unit such as a torn RF screen. During the start-up sequence, the system is designed to search for a functional RF detector and to automatically perform a functional test.


For the RF detector to work properly, it must be installed correctly on the light shield near the lamp units. 


Tips for mounting an RF detector: 

  • Each individual light shield must have at least one RF detector installed. 
  • An RF detector should be mounted no farther than 40 inches from any lamp unit. We recommend at least one RF detector for every five lamp units. 
  •  The RF detector should be placed outside of the light shield to protect it from heat and UV. 
  •  The RF detector should look into the light shield through an opening that is a minimum of 2 inches in diameter. 
  •  To protect the RF detector from UV, a piece of 1/8"-thick silicone rubber should be placed over the opening. An RF port plate is used secure the silicone rubber in place. 
  •  The RF detector should be installed with the antenna (or "nose") 1 inch away from the silicone rubber. Since the presence of metal surfaces near the detector can sometimes cause false readings, you can move the RF detector farther back in half-foot increments to find the optimum position. For this reason, an adjustable mounting bracket is recommended.  

RF Mounting 




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Cable Care 


Q. What are all the cables with the UV system?  Do they need any special care?
Every Fusion UV lamp system includes a high voltage and an RF cable assembly. Some have a third cable that supplies power to a modular blower.


Cable Care 

These cables are connected to the rear of the power supply on one end and the lamp unit, and an RF detector on the other. The high voltage cable assembly utilizes quick-connect fittings and provides electrical inputs to the lamp unit. These insulated cables carry power at approximately 4,000 volts from the power supply. 


Cable Care assembly
Cables manufactured by Heraeus Noblelight America are a high-quality cable rated at a minimum of 10,000 volts. The cable fittings are labeled and keyed so they cannot be inadvertently interchanged. The RF cable provides power and control signals to the detector. 




Regarding any special care of these cables, we recommend the following preventive maintenance:
CAUTION: Never touch any cable assembly while the system is On or in Standby. Disconnect all external power prior to troubleshooting or inspection.

  • For safety reasons and to minimize the opportunity for damage, it is important to locate and protect these cables properly. Wherever possible, cables should be routed through cable trays. At a minimum, care should be taken to ensure they are kept out of high-traffic areas where they can be easily damaged. 
  • Periodically check the cables for damage. If damage such as cuts or abrasions are observed, the cable should be replaced as soon as possible to ensure the safety of personnel, as well as for system stability. 
  • Periodically disconnect the cables and check the pins and connectors for damage. The pins should be inspected for damage and evidence of electrical arcing, and the connector collars should be inspected for any damage that would prevent a secure connection. 



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Maintenance Log


Q. What specific service or maintenance information I should be logging or tracking for my UV curing systems?
Heraeus Noblelight recommends you keep track of each individual lamp module by using the Lamp System Maintenance Log which is found in the back of your System Manual. Using this log, you can note the model and serial numbers, bulb serial number and type, along with the lamp system location, position, and any repairs or preventive maintenance performed. This logged information can be especially handy when there are warranty questions or maintenance personnel changes.


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Changing Electrical Operating Frequency


Q. Is it possible to operate Fusion UV curing systems at different electrical frequencies, or what is required to change the system to operate on a different electrical frequency (50Hz to 60Hz or vice versa)?
Since electrical power sources can differ from country to country, it is important to make certain your UV system is set up for the correct voltage and frequency. Failure to do so can result in loss of efficiency and damage to core components over time.


All Heraeus Noblelight lamp systems can be operated at either 50Hz or 60Hz, however some models require modification in order to operate properly. 


Heraeus Noblelight models Light Hammer 10®, Light Hammer 6®, VPS/I600 and VPS/I250 require no component or wiring changes. The power supplies in these systems recognize the frequency at the initial start up and are self-adjusting. 


The current production models F300S and F300SQ require a minor wiring change of the high voltage capacitors when switching frequencies. Some older versions of the F300S and F300SQ may require changing the high voltage capacitors. 


The F450T and F600S require a change of high voltage capacitors and transformers to operate at a different frequency. 


Irradiator modules are not frequency dependent with the exception of the model I250B (the irradiator in the F450T and VPS/I250 systems), which requires a different belt and pulley kit for the integral blower depending on the frequency. 


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