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g4 led 240v lamps not working but only flashing?

Postby remelad » Thu Dec 24, 2015 6:52 pm

Hi all, have just swapped out some G4 halogen bulbs for some G4 led's
They are 240 volt one's, fitted to a chandelier of which there are 7 in total.
My problem is they will not light up but only flash quickly when the power is turned off. However if I replace one of the led's for a halogen then the remainder of the led's will light up. They are not on a dimmer switch.
Could anyone shed any light what could be the cause.
Thanks in advance and Happy Crimbo to all
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Postby ericmark » Mon Dec 28, 2015 6:37 pm

Are you sure they are 240 volt? I know 240 volt is correctly called low voltage and 12 volt is extra low voltage, but lighting manufacturers tend to call 12 volt low voltage even though incorrect. I would think it is hard to get 240 volt G4 bulbs.

I will guess some where there is a switch mode / pulse width modulated control box often called electronic transformers which was designed to power a 12 volt quartz lamp. These often are marked 10 ~ 60 watt or similar and will auto shut down if the draw is below 10W. Fact that it works with one quartz bulb points to that being the case.

A LED is a current dependent device and some where there is a driver which converts it from current dependent to voltage dependent this device may be a simple capacitor or resistor or a pulse width modulated chip the latter may have a huge voltage range typically 10 ~ 30 volt but the resistor needs a very carefully regulated and smoothed supply.

I found my GU5.3 fittings with LED bulbs were a failure even though a real transformer so should have worked only got around 3 months life where the GU10 bulbs never had one fail.

So although GU5.3 or G4 bulbs need a rectifier as can be put in either way around they still often need a DC regulated supply the peaks on a 50 Hz supply is too much for the LED and they fail very quickly.
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