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MR16 LED Spots flickering and flashing?

Customer Question

I wonder if you can help. A few of my Energy Saving LED bulbs (5W MR16, mixture of natural and warm white) start flashing or flickering after they’ve been on for a while – perhaps 20 or 30 minutes.

I’ve tried replacing the electronic transformer on one of the fixtures with an LED driver rated for up to 12W, but this made the flashing even worse.

In an attempt to figure out whether it’s caused by the bulb or the fixture I swapped a bulb that flashes and one that doesn’t. The same bulb starts flashing even when it’s in a different fixture.

Could it be that these few bulbs are faulty? The others are perfect so if it were possible to replace them with working ones that would be great.


Technical Tim

This is most unusual and we are perplexed. Whilst it could be the transformer or transformer/LED combination we doubt it as you have carried out some excellent diagnostic work and the issue appears to be time related due to the delay before the units misbehave. If you have has some photographs of the transformers used (need to read the writing on the units) it would be appreciated.

Generally transformers intended for use with halogen lamps don’t work correctly with LED lamps due to the very low power requirement of the LED lamps. However this usually shows up immediately and not after a delay period. Again there are differences in LED transformers and we doubt the transformer is the cause of the issue, a photo would be a lot of help.

Sorry for the inconvenience.



That’s excellent, thank you.

You’re correct ref your other email:

5w Spot – MR16, Natural White x 5
5w Spot – MR16, Warm White x 8

I’ve attached a few photos showing the transformers. There are two slightly different types of fixture so I’ve included photos of both, although the problem doesn’t seem to be isolated to a specific type of fixture / transformer.

I’ve also included a shot of the DC LED driver I tried swapping in, in case that’s useful.

Hope this helps.


Technical Tim

Many thanks for the time, effort and input from your end regarding this issue. The photos have been most helpful and have probably revealed the source of the problem, let me explain further.

Referring to the photographs of your two transformers you will notice that the specification for the transformers is 20 – 60w. This would tend to indicate that the transformers are/were intended for tungsten halogen lamps and would cater for 20w, 35w and 50w versions. The minimum load that the transformer would work with effectively is around 20w and relies on the metal filament of the lamp to smooth out inconsistencies in the generated voltage; won’t go into technical details here.

The LED units require only 5w which is far below the minimum 20w the transformer is happy supplying, any less than 20w and the transformer generally doesn’t work correctly, assuming the lamp has failed. Usually operating a transformer of this type with a low load as provided by a 5w LED with no metal filament causes the transformer to “complain”, the usual symptoms we’ve come across are constant flashing on and off or just one major flash at switch on; there are others. However as there are more different transformers out there than there are seeds in a pomegranate all is not so usual and we’ll look into this further once we have the LED units back.

We suspect that the combination of transformers and lamps has worked for some strange reason but outside normal operating conditions and that some damage may possibly have occurred of an unknown nature, most probably to the LED lamps which I understand are being totally replaced. I would most strongly suggest that the transformers are replaced with LED compatible types to prevent further failure and inconvenience to yourself.

However before you do this I hear you say “ What about the one specific, special LED transformer? There is no difference in effect”. Could I ask you to confirm that the LED transformer you have works correctly all the time with a ”good” LED lamp and confirm what it does with a “suspect” LED lamp? Does the suspect lamp flash immediately or after a period of 20 – 30mins? This latter case would tend to confirm that the lamp(s) are damaged somehow.

Look forward to your comments on this matter.

If you require any further information or assistance please do not hesitate to contact me.



Thanks for your comments and for taking the time to investigate so thoroughly. That all makes perfect sense.

I’ve just tried reinstalling the LED driver in one of the fixtures as requested. All four of the “good” lamps I tried (i.e. I’ve never seen them flash before) started flashing rapidly as soon as they were switched on, exactly the same as the known “bad” lamp. Perhaps this indicates that they’re all damaged to some extent, or maybe the LED driver itself is faulty – perhaps caused by being connected to the original “bad” lamp?

I don’t have another LED driver to hand, but could order one. However I do have plenty of regulated 12V DC bench power supplies – would you like me to try some experiments with “good” and “bad” lamps using one of those? Fully understand if you’d rather I don’t.


Technical Tim

Thanks for the info, seems things aren’t going in the right direction, let me elaborate.

1. The 20-60w transformers you have should NOT work with the low power LEDs. They should either flash on or off or just flash once at power on. They should not continuously illuminate the LED due to the minimum power requirement. We live and learn though.
2. The LED specific transformer you have should work correctly and not flash at all.

Seems that life isn’t performing as it should though.

We’re erring on the side of caution with regards the LEDs being “damaged” by the transformers intended for halogen lamps, we’ve never had it occur previously but we should factor the possibility that it might have caused issues, hence the replacement. My concern is that there is something more amiss and the replacements will perform just as the units you already have.

Could I as you try a little experiment “Blue Peter” style as shown in the attached, you won’t need the radio. You’ll need a PP3 battery and connect the LED(s) as shown, do they flash or illuminate normally? I know it is only 9v not the 12 volts that the LED needs but you will find that the lamps do work as shown.

Sorry you are having this problem with what should be relatively straight forward.

Let me know the outcome if you would.



Thanks for this. I’ve tried connecting one of the bulbs that’s known to flash on the LED transformer to a 9v battery – it worked fine with no flashing.

It took ages to find the right model of Sony radio and an Audrey Hepburn poster 🙂

Would it be useful for me to send you the LED transformer along with the bulbs so you can take a closer look? Of course it’s possible that it’s simply faulty as I’ve never seen it work correctly.


Technical Tim

Thanks for your feedback, doesn’t actually prove 100% but certainly heading in the right direction.

Here is an update with some additional tests we have run with more electronic transformers received today; our original tests were based on transformers from a few years back.

We’ve run a series of tests with different LEDs and transformers, some electronic transformers work with 5/6w LEDs even though the minimum load is stated as 20w; we’ll run them for extended periods to determine the long term effect. A slight flicker from the LED may be noticeable with some transformers due to the “incompatibility”. Please note we refer to flashing as an on/off situation where as flicker is a slight rhythmical change in the level of brightness.

Some transformers won’t work correctly at all with LED lamps.

We suspect that the transformers you have, two different types I believe, will perform differently. The flashing (or is it flickering?) will most likely be some imbalance/incompatibility between the LED and the transformer load showing up once either/or or possibly both the transformer and the LED have warmed up. We haven’t come across this before but again theoretically the 20-60w transformers shouldn’t work at all although we suspect if they do they are not working correctly hence the issues arising.

The LED specific transformer you have which flashes is most unusual and we suspect something is amiss with it. You certainly can send it over to us if you would and we can let you know our findings but effectively the 12v dc LED transformer should work exactly in the same fashion as the 9v battery test. It may be the transformer is defective but that should be easy to confirm.

We can certainly recommend http://www.myswitchshop.com/index.php?main_page=index&cPath=44_50 transformers. The 50w version should power up to 4 LEDs although this would obviously require additional low voltage wiring run from the transformer to the lamps. Mention us if you propose purchase.

Needless to say please ensure that the circuits you are working on are electrically isolated and don’t rely on the switch to isolate the circuit, it may be wired in the Neutral return rather the Line Feed.

If you need further assistance or information please don’t hesitate to contact me.

LED’s have wiped out my DAB radio signal

Customer Question 

I have a question/problem for you, i have purchased your 8 of your led mr16 spots and have put them in my kitchen as a straight swop for MR16 halogens, where as they work
well they completely wipe out my dab radio signal! is there any thing you can suggest? i assume its down to the 12v drivers that are still on the existing fittings but i’m not sure if changing them will cure the problem, could it be the bulbs themselves?


Technical Tim

Thanks for the information and sorry to hear you are having an issue with the recent purchase. Let’s try an elimination test with your assistance if we can to try and localize the issue.

Could I ask the following

Could you try the little test as shown in the attached Battery Test document and let me know the outcome please. Pay attention to your signal strength before and after. The Video shows a live test performed with a couple of lamps.
What type of fitting are the lamps installed in? Are they individual ceiling recessed types, track lights or clusters?



i tried the battery test and there was no signal loss, the lights are fitted to 12v transformers with mr16 fittings they are individual ceiling recessed types. i couldn’t get the video to work on my mac by the way.


Technical Tim

Thanks for the feedback, you may be in with a chance then, but let’s not count our chickens before they are hatched.

All electrical products generate electrical signals, some wanted some unwanted, The unwanted ones must not rise above a certain threshold in order that the products perform correctly and may be certified as meeting the required standard, of which there are many even for a single product.

Similarly an electrical product should also be immune to electrical signals impacting on it that do not exceed agreed levels and that product still performs correctly.

Yes, we are aware that there are is lot of talk amongst various parties and user groups on the Internet about issues relating to LEDs and interference, some helpful, some less so.

With the little test you have performed the LED seems to have minimal impact on your radio, this would tend to indicate that both the LED, radio and reception signal level are acceptable. A low received signal strength may well cause issues, as would a poorly designed LED or radio receiver. Could I ask if the radio you have is battery operated or has a separate power adaptor which plugs into the power socket?

The issue is likely to be caused by a combination of more than one component in the complete set up of received signal strength, radio (with power supply), LED, existing power supplies for previous lamps and interconnecting wiring.

In order to try and resolve or at least minimise the issues you are experiencing would it be possible for you to read through the attached note and fit filters as indicated which we would supply? Please note that the filters must be fitted as shown with the turn of cable around the outside in order to function effectively.

The filters will minimise any interaction between the LEDs and the relevant power supply reducing and, minimising any electrical “interference”  that may be radiated by or conducted along the power cabling.

I have attached a file for the more discerning Apple enthusiasts, apologies for the oversight, you will need sound. The LEDs shown in the clip are not the ones you have but from one of our previous ranges, the LEDs you have have slightly better performance than those shown.

If you require any further information or assistance please do not hesitate to contact me.

Slight delay when turning on the LED Spots, is this normal?

Customer Question

One of the 5W well lit didn’t come on immediately in the kitchen tonight when I turned on – I thought it had gone but then it came on about 1min-2mins later…. have you seen that behaviour before? I will monitor but just wondered.


Technical Tim

It could be faulty but have never had any LEDs in my experience do this.

It could be the fitting/LED electrical contact. If especially the fitting has been used for halogen units the fitting and metal contacts will have been hot for some time causing discolouration and tarnishing of the spring metal contacts. Kitchens, smoking etc will all contribute to surface contamination of the sprung metal contacts.

The halogen lamp will draw approximately 0.2 amps and far more at switch on, the LED will draw 0.05 amps, far less and possibly not sufficient to break through any tarnishing/corrosion on the surface of the spring metal contacts in the holder; eventually contact has been made and the LED appears to work satisfactorily.

Try removing the suspect LED lamp and insert it in a different position and then insert/remove a different LED lamp a few times to scrape any possible tarnishing and monitor operation.  Any further flickering, delay in powering up on the fitting would indicate a contact issue, if the suspect lamp plays up in a different location it would tend to confirm a LED fault and the unit should be replaced.

Do this with the power turned OFF

My GU10 LED Spots do not work with my Varilight dimmer

Customer Question

Hi, I just received my 8x 7w Dimmable LED Spot.
Unfortunately they don’t work with my Varilight Dimmer which is suitable for dimmer LEDs. Any recommendations?


Technical Tim

Sorry to hear that you are having some issues with the recently delivered 8 x 7w LED spots and your dimmer unit.

Could you give me the specific Varilight model number you are using please so I can give you more specific advice; essentially they should all work but that is no help to you though at the moment.

Are all the lamps running off the one dimmer unit?

It could be either all the spots or some of them causing issues with the dimmer unit, it could be the dimmer unit itself or some strange combination. The Varilight trailing edge dimmers do work with the LED units so let’s try by process of elimination with a little test.

If you have any halogen spots left, remove all the LED units and put one or two halogen units in place and try the dimmer again, it should dim the halogens correctly.

If you could let me know the model and the results of your test it would be appreciated.

LED Bulbs installed on a circuit with a timer are flickering

Customer Question


I have bought some 9W e27 led bulbs from you for indoor and indoor use.

Indoors they are fine, as well as some outdoor fixtures (ip rated).  However, when applied to some of the fixtures outdoors, they flicker continuously when not turned on.  Do you know how I can solve this problem?  They are used in some traditional outdoor lantern lamps.



Technical Tim

Thanks for the communication and sorry to hear you are having a spot of bother; a most unusual issue and one we have not come across.

If you could supply a little more detail we’ll do our best to assist to resolve the issue.

a) How many exterior lamps do you have?

b) Are they all the same type?

c) Is there just one switch to turn the lamps on/off or can the lamps be turned off from more than one position?

d) What is the distance (approximate) between the lamps?

e) Is it the farthest or nearest lamps that have the issue or is it random?

f) Does the issue stay with the lamp or the lamp socket? Change the lamp and see if it makes a difference. If the flickering stays in the same location it is possibly the socket/wiring issue, if it goes away it is possibly the lamp. Note we say possibly, there are complications.

g) If you put a standard filament lamp in one position does the issue go away?

h) The flickering, can you describe it a little further please? Flickering is the lamp(s) continuously illuminated whether at full or reduced level with a fast or slow variation in perceived brightness. Flashing is the lamp fully off, with a period of illumination (brief?) followed by an  off period, t e process repeats. If it is flashing do the lamps flash at the same time?

Thanks for your help and look forward to receiving your response.



Here are my answers to your questions:
a) 12

b) yes, but some are on timers set from an internal on/off switch with a timer built into the switch
c) on and off from only one switch

d) width of our front door (standard size)
e) it seems to only happen on the lights with the timer on the switch

f) if I change the bulb to a normal filament bulb, the lights do not flash
– if I change one of the pair of lamps (controlled by one switch) to LED, and the other to a filament bulb, the lights do not flash
– if I change both bulbs to LED, then the lights flash
g) yes

h) I mean flashing (the issue only occurs when the lights are off). When the lights are on, there is no flashing
– flashing occurs very briefly, less than 0.5seconds, but there is no pattern, the flashing seems to be irregular
– the flashing occurs at the same time

One more question, what is a LED GLS bulb? I’ve seen them elsewhere on the internet. What does the GLS bit mean?


Technical Tim

Thanks for the comprehensive information.

GLS is General Lighting Service a term that refers to the “pear shaped” lamps we are all familiar with and originally was used for the glass/tungsten filament versions that generally had a lifespan of around 1000hrs, now in the process of being totally phased out be EU edict.

In response to your information and if I have read an understood correctly the issue is only with the lamp(s) that are on a timer circuit and not those that are switched on/off via a traditional switch.

I suspect that the timer switch is not of the older electromechanical switching relay type, they haven’t been around for a fair few years and you can usually hear a mechanical noise as they  operate, but will be one that uses the more modern type of electronic switch, possibly a triac. You will probably find that the design of the switching circuits in the timer is intended for resistive loads such as the tungsten filament of the GLS type only and not intended for inductive loads such as CFLs or LEDs, there may have been a note with the timer saying not for CFL loads.
In particular with LEDs and the main reason for using them, their very low power consumption, the electronic switch in the timer unit will allow a small amount of leakage current to flow even in the time off position. This leakage current will be sufficient over a period of time to charge up fully the electronic power supply in the LED lamp and cause it to flash the LED on. The flash will exhaust the stored energy in the LED lamp power supply and the process will repeat itself ad infinitum; the timing is dependent on a number of factors.

Isolating the power to the timer will prove the point. With power removed say via an isolator switch to the timer the lamp will cease to flash.

The reason the timer unit circuit functions correctly with a tungsten GLS unit in circuit is that the tungsten filament represents a virtual short circuit for the “leakage” current. The current is insufficient to power the GLS lamp either on its own or in the pair I think you have and similarly even with one tungsten GLS and one LED in circuit, the filament of the GLS unit removes the power source so that the LED unit is deprived of energy.

This effect will apply to practically all LED lamps that have a safety isolating switched mode power supply in them as ours have.

If this is the case as I suspect, then the best solution I’m sorry to say is to replace the timer unit with one suitable for inductive loads and particularly low power ones.

I trust this assists you and I hope I have understood your particular installation and your explanation, however if you require any further information or assistance please do not hesitate to contact me.

Regards and thanks

Can you have dimmable & non-dimmable LED Spots on the same circuit?

Customer Question 

How likely is it that if you have 10 spotlight fittings in your kitchen and you fit 8 dimmable Spots and then 2 non dimmable spots that this would stop the dimmable products from working properly?

It seems to be the case in my kitchen that all my lighting fittings must be dimmable or not dimmable for the LED’s for them to work properly.


Technical Tim

In answer to your question “How likely”? The answer is quite likely.

Trying to get dimmable LEDs (electrically reactive components) to work with dimmer units designed for incandescent (resistive component) is a job on its own and doesn’t always work due to the design of the dimmer and the design of the LED unit; the electrical power supply designer of the LED may have a totally different concept of what electrical design of dimmer he intends the LED to work with.

Throw another different type of LED into the situation with a different power supply and method of operation and don’t be too surprised that there are issues. Bear in mind that even a lamp from the same manufacturer may cause issues due to different circuit design changes/different designer between the units.

Bear in mind that as well as a danger of dimmable LEDs (or CFLs) damaging the dimmer or themselves there is a strong possibility that the system will not work as the user imagines it will, complicated even further by the fact that the system may well work with 8 lamps but fail to function with 9.

Is there a way to check the minimum load requirements of our existing transformers?

Customer Question 

I have MR16 fitting LED Spots. If each fitment has a transformer of it’s own, is there a way to check the minimum load requirement before we sort replacements?


Technical Tim

The honest answer is that it is impossible to check and be 100% certain purely because there are so many different transformers out there. Most, but not all electronic transformers require a minimum load to operate, it depends on the design/construction but for simplicities sake let’s assume that we are talking about the single transformer for each lamp scenario.

Some transformers are marked 20-50w and it is fairly safe to assume with those that there is a minimum load of approximately 20w required for them to function. In all honesty they will probably work with 15w but probably not 10w and certainly not 5/6w. The results will either be no light at all, maybe a quick flash at switch on or continued flashing every few seconds; certainly this is what I’ve experienced, it all depends on the circuitry. Other transformer types have no markings as such and it is a wild stab in the dark as to whether they will work or not.

Can you provide us with some images of the current transformers that you have installed?

Please note NO work should be carried out on live electrical circuits, ensure power is turned off correctly at the main electrical distribution board. DO NOT assume that the light switch effectively isolates the lighting circuit you are about to touch.

LED’s bought from another retailer have failed with blackened area between the two terminals, help!

Customer Questions 

I bought some LED Spots from another online retailer and had some issues with them and their laughable ‘technical support’, so I hope you don’t mind me contacting you as I’m worried by something. One LED failed quickly another a few more after 10 months. All the failure had a greatly blackened area around and between the two terminals – see attached photo.  It had also blackened the light fitting in the same area also. The photo may give you some idea about the reason for failure.  I’ve no idea who made that failed bulb as the box contained no name and on the barrel of the bulb it says 6W 230V AC DIM and underneath that it says GU10 CE ROHS.  Presumably the DIM indicates that it’s dimmable.


Technical Tim


We need you to immediately stop using the bathroom lights.

Turn off the power at the fuse box by either removing the fuse or the breaker or if not sure turn ALL the household power off.

Having made sure that the power is isolated, examine ALL the lamps and fittings in the bathroom and look for similar blackening.

If there is any blackening on the fittings use WD40 and an old toothbrush and remove the blackening. If it is not possible to remove it then I would advise that the base is replaced. Any lamps that show blackening should be replaced and not cleaned.

If unsure of procedure utilize the services of a qualified electrician.

The blackening is caused by electrical discharge between the two metal parts of the lamp causing carbonization of the surface and if permitted to build up will provide a more conductive circuit path which will permit more current to flow leading to an increase in current, heat and the potential of fire due to the flow of power.

I have no idea why this has happened from the photograph provided but it is an immediate source for concern especially considering the units are in the bathroom and there is a void, or should be above them. If the carbonization continues, the lamp holder will become hot, the carbon will smoulder and will continue to smoulder even if the power is removed.

IF the blackening cannot be removed electricity will continue to leak across the blackening leading to a breakdown and potential fire and the part MUST be replaced. Take no chances.


Further thoughts on the subject.

It is likely that the issue has possibly been caused by poor contact between the pins on the lams and the spring contacts on the holder although this is not apparent from the small photograph. It is possible that the lamp has not been fully twisted to locate the lamp correctly in the holder causing poof contact and electrical arcing resulting in the deposits observed.

It is essential that the holder is examined for any signs of deterioration of the metal contacts such as pitting/burning/corrosion; if in doubt the holder should be replaced, the cost is minimal and the possible consequences are frightening to consider.


I do appreciate your consideration and help.  You could be right about the lamp not being fully engaged as the bulb holders have only about a millimetre or two of clearance from the width of the bulb and as they are fully recessed it makes it difficult to use the fingers to apply enough turning force.  The same applies of course with removal, which is one of the attractions of long life!  The old Halogen ones had a smooth glass  front that enabled use of a suction pad, but the LED ones won’t accept that method of assistance.

I am making urgent contact with a competent electrician to get things checked through.

I have had a “rated people” electrician carry out a full examination of my bathroom lighting system with the conclusion that all’s well and no work needed . He said that the cowlings were good fireproof ceramics and very safe. He also checked in the loft under the insulation to make sure evidence of excessive heat wasn’t present.

One strange thing though – the lamp that failed and was supplied  by my local electrician was difficult to remove from the fitting as instead of disengaging the pins when applying anti-clockwise motion the glass element of the lamp revolved, unscrewing and leaving the ceramic base plugged in.  I had to press upwards hard and then revolve to achieve disengagement.  That was another bad mark against the failed bulb!


That’s good to hear you have it sorted, you can never be too careful with electrics.

I bought some dimmable LED’s from you but they don’t appear to be working correctly, is it my dimmer?

Customer Question 

I bought some dimmable LED’s from you but they don’t appear to be working correctly, is it my dimmer?


Technical Tim
One thing I should stress as we discussed is that non-dimmable LEDs must NEVER be used in a dimmer circuit even if the “dimmer function” is not used and the dimmer control is turned to full; it is not the same as having a simple on/off switch. Not only will the LEDs not dim as expected they will not perform correctly with the modified electrical supply from the dimmer even at full output. The simple result will be failure of the LEDs, dimmer unit or both. As you commented you have heard a noise from the dimmer, this is indicative of imminent trouble.

The most probable reason the current dimmers that you have work erratically with the dimmable LED devices I understand you have is due to the minimum loading requirement of the existing dimmer units which are intended for incandescent/halogen lamps.

The dimmer units will have a MINIMUM load requirement of around 30w although this will vary from individual unit to individual unit. If the load on the dimmer is less than the minimum requirement than it is more than likely the dimmer will not perform as required and as expected, typically the LED unit will flicker, will not dim at all or will only have a limited range of dimming. As you have a number of dimmers I would not expect them all to perform identically due to tolerances between individual dimmers and the total load presented by the LED lamps which will also vary due to individual differences.

Now if I understand correctly from our conversation, you have a particular unusual arrangement with regards the loading you have on your dimmers in so much as you only have 2 LEDs per dimmer circuit which presents a theoretical load of 14w which is far below the minimum load of a traditional incandescent dimmer unit. The results of using a low load with a dimmer will be variable to say the least.

We have actually set up a special test circuit to confirm our previous findings and we can confirm that a specified dimmer will work correctly and dim from full off to full on with a low load as you require for the 2 LED units; even LED dimmers have a minimum load requirement and your requirement of 2 LEDs per dimmer is close to this value especially taking product tolerances into account.

For the dimmable LED lamps you have you will require dimmers from the V-Pro Professional Universal Series which have a Prefix code J.

You mentioned that you have 4 dimmers on the one white (twin) panel so a 4 way dimmer unit in white would be JQDP254 on page 6.

If you require the panel so that there are no screws visible you would require JDQDP254S on page 16.

Your requirement also for a 4 way panel with 2 simple on/off switches and 2 dimmer units probably poses a problem at the moment though and it may be better to go for the simple option of duplicating the 4 dimmer panel above and using dimmable LEDs; non-dimmable LED’s will not work.

These dimmer units have a programmable feature, explained in the fitting instructions which permits them to be set for varying lamp numbers in order to achieve the full and correct dimming range from full off to full on.

I hope the information is of some use to you. If you require any further information or assistance please do not hesitate to contact me.

Can i use LED’s with an air vented heat dissipation system in enclosed fittings?

Customer Question

Hi, I’m looking to buy some LED Spotlights and the ones I’ve been looking at using an air vented heat dissipation system. All my fittings in my property and enclosed and I’m guessing that this will present a problem with air flow? How big a problem is this and are there any solutions ?


Technical Tim

The problem is in the assumption that heat rises, which of course it does, however the rising warm air has to be replaced by cooler air in order for the cycle to run efficiently. Removing the glass of the fitting isn’t much of an issue however the fitting cover has a lip so that the small gap between the body of the lamp fitting and the body of the LED lamp is obscured. The lamp fins therefore have to try and cope with warm air rising and cool air descending at the same time, which generally doesn’t work too well. The air flow becomes chaotic and the amount of heat removed from the fins of the lamp decreases severely; the LED lamp heats up.

I’ve made a modification to the lamp fitting and am running some tests to see how it performs and will let you know in due course, but as it stands even with the glass removed the LED runs abnormally hot.


Technical Tim

I made some Modifications to the unit in order to provide some venting effect and airflow over some of the fins at least; the smoke test indicates the effectiveness of the venting.

Require a minimum of 6 off 7mm holes drilled into the rear of the lamp as per photograph, remove the 2 screws which secure the GU10 lamp holder first and hold ceramic base and connecting wires out of the way before drilling. Holes are equidistant and positioned around 2 existing tapped holes which secure ceramic base.

No need to paint the inside of the unit matt black to aid heat dispersion at the body of the lamp holder remains cool in comparison with halogen lamp and method of heat loss is totally different.

Some housekeeping will be required at least annually to ensure that there is no build up of dust on the lamps, fins in particular, as this will reduce the effectiveness of the cooling.

This is purely a suggestion based on what I believe was the brief you supplied – using fully enclosed fittings which without modification are certainly non-starters as far as the lamps are concerned; a disaster in the making, even with halogens the limit is 35w.

I highly recommend not using the fittings as they are and in all reality, no modification is going to make the lamps work as they should and will probably void any warranty.

Remove the glass and whist it does improve matters the effect is minimal.

The vent holes in the fittings are a SUGGESTION to improve matters in order to prolong the life of the lamp, it is not a firm guaranteed solution to improve the reliability and performance of the product in enclosed fittings and we do not recommend it.

My new LED Lights interfere with my DAB radio

Customer Question

A problem has ‘cropped up’.  The new lights interfere with my DAB radio.  Can only get BBC stations with any certainty.  Signal not brilliant here generally but now is very definitely linked to on/off of lights. Hopeful that by waltzing around the kitchen which is reasonably large I will find an ok spot.


Technical Tim


I’ll need a few questions answered before I can advise further.

How many lamps do you have?

Are they in the kitchen?

What type of DAB radio?

Is the radio mains powered or battery powered?

Does it have a telescopic aerial or it the aerial external to the house like a TV aerial?

What is the nature of the interference, what does it sound like?

Does it stop the radio receiving stations, some or all?

A quick initial check from , BBC postcode checker for DAB availability indicates that your area at the moment does not have DAB coverage, i.e. it might have but it is not of acceptable quality. I believe the nearest transmitter is to the north west of Exeter.
I’ll carry out some initial tests and factor in the additional information. Generally though, all electrical products will generate electromagnetic disturbances but they must NOT exceed certain limits for the particular product classification; the lamps do meet the statutory requirement.

Conversely, products must also be manufactured to be immune to electromagnetic disturbances as long as they do not exceed a specified level.

Different manufacturers use different methods of converting the mains voltage to the low voltage required by the LED units themselves.



Found a spot in the kitchen for my radio that works ok – so my problem solved.  Although I prefered the radio where it used to be.


Technical Tim

Glad that you have found a sweet spot in your kitchen where the radio works, however if you let me know how many lamps you have I’ll arrange to have some ferrites shipped off to you as per the attached PDF.

These should have some effect on the reception you have (or haven’t) there.

We have carried out substantial tests with our products regarding “interference”, all electrical products generate electromagnetic signals when functioning and in order to be put them on to the market they must meet certain criteria for their specified class of product so as NOT to exceed the maximum level of electromagnetic disturbances stipulated in the regulations. Our products do meet these product approvals and furthermore have been tested by us in real world situations with various radio receivers operating on various wavebands, DAB, FM and MW.

Under normal circumstances providing the radio receiver in question is receiving a reasonable signal strength there should be no interference whatsoever.



8 x V7 7w LED (warm white).  Thanks for the suggestion, it would be nice to have the radio where it was before..


Technical Tim

We’re sending some units off to you though don’t know when you will get them though I’m afraid due to the time of year and elves busy.

Please let me know how you get on with them if you would and any relevant comments.



OK, have given up on the ferrites as trying to fit them to light units will require them to be in the ceiling and the whole lot unscrewed.  Life is too short and I’m too lacking in skills electrical.  Thank you very much for thinking of them though..

Apart from the radio bit all lights are still are working fine and long may that last.  Never had all these problems with the old fashioned ones, I feel quite the pioneer.

Finally, I want to leave some stupendously good feed back for you but there is no obvious place to leave it, or is it me?  Please advise me where it needs to be left.  Thanks.   Happy New Year proper by the way..


Technical Tim

Sorry you are having issues with the ferrites there, I thought it would be fairly simple, obviously not. You must have different fittings in the ceiling from the ones I was led to believe you had, similar to the ones in the attached photos, could you let me have a photo if possible please?

We have thoroughly tested the units in real word situations with FM and DAB radios in various locations and whilst theoretically it is possible for any LED unit to cause interference in certain circumstances it is most unlikely; no consolation for you though.

I actually have a DAB radio and 6 lamps operating without issue and suspect the problem is a combination of various factors, a photo of your LED installation would be much appreciated if at all possible.

My colleagues will contact you regarding the non-technical bits, thanks for your support and feedback.



Google Endon 654 sc as this will find a picture of one of my light fittings. The other fitting is identical other than having 5 bulbs rather than 4.

Did you see the video clip sent to chris stimson (name from memory, may be slightly different!) as to lights on/radio off and vice versa?  For your info.


Technical Tim

Thanks for the information and I see your problem with the track lights you have. It is obviously not possible to fit the ferrites to each light as intended, the only option is to fit one to the common incoming power cable which is under the circular cover/in the ceiling; something for someone with electrical knowledge I am afraid.

Yes I have seen the video, many thanks for that.

You may wish to try and fit one of the ferrites to the power cable feeding the DAB radio as an experiment though. Fit the ferrite unit to the white power cable as close as possible to the rear of the radio where the cable enters the radio itself, see photograph attached. You should be able to wrap/loop the white cable through the ferrite approximately 4 times, just feed it through and then round the outside and back through the centre again.

I’d be interested to hear the results from you but to be honest to stand a better chance of reducing any possible interaction it will be necessary to fit a ferrite as suggested to the power cable as suggested above or fit an external DAB aerial to ensure you receive the required signal level that the radio requires; go for the ferrites first!

I am a retired techie and have some questions before buying LED’s for our kitchen extension

Customer Question 
I am a retired `techie’ (B Sc, Eng) and we have used CFL lights over the years .also I dabble with a soldering iron and have built valve and transistor amplifiers, zero crossing Triac controllers, etc over the years.
We are having our kitchen extended, and looking at lighting options.
1) I’m not sure that the GU10 lamp style was ever really intended to accommodate the rectifier and capacitor components to convert 240 volt ac (rms) to LED type DC voltages. This is even more relevant if the components are `potted’, which impedes heat dissipation …..
2) The other option is  `integrated’ LED lamps, perhaps with an electronic driver circuit external to the LED assembly; however, these seem costly, and I would not want to be stuck with non standard holes in the plasterboard in the years to come, if/when a particular brand/type becomes obsolete ?
3) How long do you test your bulbs for? ie MTBF data ?
Any further comment on where to go for a new installation would be appreciated !


Technical Tim

1) Think you may be pleasantly surprised in the developments of miniature switched mode power supply units used in the “proper” LED units from recognized manufacturers. With and efficiency of 80 -85% and total input current in the order of 50mA, we’ll let you do the maths. We deal with tens of thousands of lamps per year and the relative failure of lamps, and yes there are bound to be failures for any number of reasons discounting misuse and abuse, such as infant mortality heavily biased to LED failure and not power supply issues.
2) You have not considered the third way. Use the 12v low voltage of the lamps, generally referred to as MR16. Very little electronics if you are concerned about heat. One switched mode power supply supplies 11.5 volts via suitably rated cable to the lamps, or if you prefer a traditional iron copper transformer suitably rated.
3) We have a number of ongoing real world tests in progress stretching back several years. A typical test we can give you firm figures for, not manufacturers extrapolated figures is just over 148,000hrs MTBF with a 2:1 on off ratio of operation.

Are there any changes to my setup that would improve the performance of your 7w LED Bulb?

Customer Question

Hello Well Lit

I ordered three of your 7w Dimmable LED Bulb (#5048) Colour: Warm White (2700k), Fitting: B22 – Bayonet Cap.  The model delivered was the 270º LED Omni A60 dimmable bulb.

I am not as impressed as I was expecting to be with the quality of light and dimming performance.  I have hand them installed in three MK ceiling pendants in a new kitchen, wired on their own circuit to a Varilight V-Pro dimmer switch.  With the dimmer fully turned up the output actually lowers and flickers (the lights seem to be brightest with the dimmer at around 70%), whilst with the dimmer down to minimum they are brighter than I would like, and they flash once at full brightness when being turned off.

The rest of the lighting scheme is made up of LED downlights from led-lighthouse which have a normal dimming curve from zero to full using the same type of dimmer switch.  I was hoping for the same dimming behaviour from the pendant lights.

Are there any changes to my setup that would improve performance, or would another bulb type work better in this environment?



Technical Tim

Sorry to hear you are having a few problems there with your new LEDS, a couple of questions if you don’t mind and I’ll keep it brief and to the point.

1.       Are all 3 lamps on the same dimmer unit?
2.       Are any other lamps fitted on the circuit?
3.       What lamps were there before you replaced them with our LED units, were they incandescent or LED?
4.       If they were incandescent you may find the intelligent control circuitry in the dimmer unit has been “too clever” and is in the wrong mode and has locked on to the previous lamps fitted and is not updating. Do a factory reset, if you don’t have the instructions they are on the Varilight website, just entails clicking the dimmer on  and off in a certain order. This will reset the dimmer unit to factory values. Once set to factory default which is trailing edge dimming and correct for most LED units, certainly our units, the minimum illumination level you require may be set as desired following the instructions if the factory value is incorrect for your usage.

Look forward to your response.



Hi Tim,

Yes, resetting did the trick, they are now performing fine. The dimmer must have been stuck with the previous bulbs’ setting.

Do you do the same bulb in a 4000k cool white?

Thanks for the help, have a great Xmas


Technical Tim

Glad to hear it is all working now.

Our sales team will contact you regarding your enquiry and stock situation on Monday.

Compliments of the season to you all.

One of the LED Bulbs i purchased from you has blown

Customer Question 

Dear Sirs

I regret to advise you that one of the bulbs which I purchased under the above order has “blown”.  This is most disappointing considering the length of time promised with your product.  Fortunately the failure of the bulb did not affect the fuse in the plug.

I should be interested to have your comments.


Technical Tim

Sorry to hear you have had an issue with one of our lamps, our sales department will be contacting you separately regarding replacing the unit and requesting return of the failed unit for examination and report.

Could you perhaps give me a little information on the lamp/dimmer unit it was used with please?

Was this a standard table type lamp holder with a separate dimmer unit that permits total control over the dimming range?

Was this a combined lamp/dimmer unit which has 2 or 3 pre-set levels that are control by touch?

Was the lamp in a ceiling type fitting with a wall type dimmer?

If the latter case was there 1 of more lamps in the circuit?

Look forward to your response and any other relevant information you can supply.





Thanks for your response.

The bulb was used in a standard table lamp with no dimmer involved.  No problem has so far been experienced in a second bulb similarly use.


Technical Tim


Thanks for the information provided and I am sorry to hear that you have had a failure, this is most unusual and whilst it is obviously inconvenient to yourself it should not be a cause for concern. A post mortem on the failed unit will identify the cause of the issue.





Having received a replacement bulb I have today posted back the faulty one.

I would be interested to learn in due course the reason for the failure.


Technical Tim

Thank you for returning the failed unit which has now been inspected.

It would appear on initial examination that the issue is due to an incorrectly functioning power unit and not with the LED pack which is responsible for illumination.

This is to my knowledge the first unit of this type that has experienced failure and we will be running some further tests in the not too distant future.

Accept our apologies for the inconvenience which as we have indicated is out of the ordinary and thanks once again for you assistance.


Using a dimmable LED in a touch dimmer lamp

Customer Question 


I’d like to use a dimmable LED in a touch dimmer lamp (because when filament bulbs blow they often break the touch dimmer).

I’ve put in one of your E14 candle bulbs and in position 1 there is no light, position 2 is very dim, and position 3 is medium dim.  I tested with a filament bulb and the 3 3 positions give low, medium, high light.

I’m not sure if changing the LED wattage would help.

Do you have an LED which solves the problem of too low light in a touch dimmer?  Is there a golfball LED which you know works?



Technical Tim
Sorry to hear you are having an issue, it might change how the “dimmer” operates by changing the wattage of the lamp, however the “dimmer” itself is probably the stumbling block.

The touch dimmer circuit generally is a specialized version of the traditional rotary dimmer unit that is continuously variable from fully off to fully on. However the circuitry does rely on a certain amount of electrical current flowing through the circuit to the load to function correctly as intended. You will probably find in the instruction accompanying the table lamp that there is a specification that the unit is intended for use with incandescent lamps only and stating the permitted wattage.

The problem is that the dimmer circuit is designed for specific loads presented by the wire filament of the traditional lamp, the low power requirement of the LED lamp upsets the intended operation/operating levels of the dimmer as you have found. Depending on the design of the dimmer circuitry from units we have investigated the response is variable ranging from the results you have encountered to the lamp operating at almost full brightness at all settings with very minimal dimming.

We are investigating the matter further and whilst there is a partial solution with regards LED lamps, these are intended for visual background lighting effect only and not suitable for reading and the usual activities associated with table lamps. For our reference is the dimmer unit part of the lamp itself or is it a separate unit mounted on the supply cable to the lamp?

We are quite surprised that you note that when the lamps you have been using “blow”, we assume filament ones, that the dimmer unit is damaged. This tends to indicates a defect in the dimmer unit, lamps do fail and a well designed dimmer should adequately cope with lamp failure which is normal in the course of operation.

If we have a more positive solution we’ll advise you accordingly, however should you require any further assistance or information please do not hesitate to contact us.

Is your LED Bulb affected by flickering and buzzing like other LED Bulbs i have tried?

Customer Question 
I have been looking at the “High CRI” LED 7w dimmable bulb at this web page:

Many LED (and CFL) low energy bulbs have flickering and buzzing noises when dimmed; can I ask how much this bulb is affected by that, and also compared to other LED bulb brands?

Thanks in advance for any answers you can give
Technical Tim
Thanks for the interest and the technical question.

Buzzing/whistling in particular is indicative of issues of incompatibility between dimmer and load (lamp) and under normal circumstances should not occur if units are compatible. Note that overloading a dimmer unit with a load that exceeds permissible ratings can also give rise to noise, most if not all in both cases coming from the dimmer unit.

Generally if there is noise, primarily from the dimmer pack and possibly occasionally from the lamp(s) it is advisable not to operate the units together without seeking assistance.

We, and others, have exhaustively tested our lamps with commonly used dimmers used by electrical installers and found them to operate satisfactorily with respect to noise and dimming ability, free from flicker, over the full operating range. Regretfully we cannot comment on the performance of lamps from other manufacturers for obvious reasons.

There is a tremendous choice of dimmer units available and it is impossible to test all, some have been installed and used well before the advent of CFL and LED lighting and intended only for incandescent lamps only. As a generally rule of thumb dimmers have a minimum (and maximum) load rating, compliance is essential for correct performance.

Older units may have a minimum loading of 25-40w and are generally intended for use with incandescent lamps. They will not work correctly with loads less than the specified minimum and will certainly not work with low energy devices such as LED lamps which use so little power. The filament of the lamp actually is part of and therefore essential to the operation of the dimmer.

Certain dimmer units not intended for LED lamps may actually work satisfactorily without noise but again because of the low power requirements may not dim the unit over the entire operational dimmable range. Typical operation under these conditions is indicated by the LED failing to extinguish at minimum settings on the dimmer unit and not responding until the dimmer is well advanced.

We are aware of and have tested dimmers, some described as digital dimmers, that are manufactured in the Far East that purport to effectively dim LED lamps which not only don’t but seem to have difficulty in dimming incandescent lamps, such is the variety of units available.