Halogen bulb not working - ruled out bulb, transformer, and ceramic holder. What next?

Discussion in 'Electricians' Talk' started by jvvgh, Jan 11, 2022.

  1. jvvgh

    jvvgh New Member

    I’ve got a set of 7 spotlight bulbs in my kitchen, mostly MR16s. Once of them had been intermittently fading on and off (after being switched on for a while) so I tried changing the bulb and the new bulb didn’t work at all. I figured it might be the transformer, I’ve changed the transformer for a couple of the others in the past, so I bought a new one and fitted it but still no light.
    I decided to test the ceramic holder by switching it into one of the working spotlights and it still worked so I know the holder isn’t faulty.
    If it’s none of those what might it be?!
  2. terrymac

    terrymac Screwfix Select

    Supply issue. Measure the voltages present at the transformers primary.
  3. Wayners

    Wayners Screwfix Select

    Transformer tested here in youtube video, so you can copy.
    As said these aren't the best or safest way to test so go careful but follow the demonstration with a cheap tester and find out what's going wrong

  4. McSport

    McSport Active Member

  5. jvvgh

    jvvgh New Member

    Thanks, will give this a go!
  6. jvvgh

    jvvgh New Member

    Hm ok, sounds like a good option, particularly since half of the other spotlights are GU10s. Is it as simple as connecting a GU10 holder from the junction box?
  7. McSport

    McSport Active Member

    You have 230V going to the Transformer.
    Bin the Transformer and MR16 Fitting.
    230V to the GU10 Fitting. GU10 LED Bulb. I prefer the Warm over Cool.
    Cool LED is a bit Blue. Great in the Shed/Garage.
  8. MGW

    MGW Screwfix Select

    OK we call them MR16 but in real terms that only applies to quartz halogen as most LED lamps don't have a multi-faceted reflector so are not MR16, but both G5.3 and GU10 I would call MR16 compatible in the same way as PC compatible with computers, technically all PC's are made by IBM as it is a trade name.

    So in the main in UK GU10 is 230 volt AC and G5.3 is 12 volt either AC or DC, but all are MR16's.

    The 12 volt supply was normally a toroidal transformer, but then the electronic transformer came out, which regulated the output voltage, and had an output in the kHz range, so this limited the length of cable electronic transformer to lamp, typically 1 meter, but because more stable voltage the quartz halogen lamp lasted longer. A better name would have been power supply, as although they contained a transformer and clearly did transform not only voltage but also frequency, they had not only a maximum output, but also a minimum output. Typically 20-60 VA.

    The lighting industry seem to have set out to confuse, naming new products after the old, and so we have drivers, ballasts, transformers, electronic transformers and one needs to carefully read the label. So I buy a bulb clearly marked 50 W, but if you look more carefully in small writing it says 4.2 W 345 lumen. So even with large writing saying 50 W they are not, may be equivalent to 50 watt tungsten, but looking at a GU10 bulb in front of me, it says 7W FLU 2700K 220-240V~ 50/60Hz 50mA the PRO-LITE bulb does not give lumen output, but since the compact fluorescent lamp came out between the quartz halogen and the LED one would think the LED should say what size CFL it replaces not tungsten.

    To my mind the lighting industry are cheating, I looked at a 22 watt LED fluorescent tube replacement and it say
    but the output was 3000 lumen and the 58 watt fluorescent tube it replaces was around 5200 lumen, can't compare with tungsten as tungsten would not fit in the fluorescent fitting. Fluorescent with an electronic ballast were around the 95 lumen per watt, and with magnetic ballast around 90 lumen per watt. Why the advertising agency has never stopped it I don't know.

    But with a 20 - 60 VA electronic transformer a LED bulb marked 50 watt (4.2 watt) will not work. You can now get electronic transformers marked 0 - 60 VA they will likely work, however it could become a transmitter.

    Moving to GU10 depends on wiring, the rules say only lampholder suspended from a point in wiring (ceiling rose) can omit the circuit protective conductor (earth) so even when the GU10 does not need an earth, there needs to be one available, been like that from 1966. Often the G5.3 did not have earth core in the wiring, so to convert from extra low voltage to low voltage means new cable being run.

    I am not saying I would never convert a G5.3 to GU10, but I would not tell some one else to do it without providing an earth.
    jvvgh, PhilSo, Roys and 1 other person like this.
  9. Roys

    Roys Active Member

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