Hi there, I have recently moved into a house with an attic conversion that has around 15 GU3.5 bulbs 50w installed. Four of them weren't working so I replaced them with 35w bulbs (all I could get when I remembered to buy some). All four flash/blink when I switch them on. I suspect I know the answer but is this because I've installed 35w instead of 50w? I've left them switched on twice for around 15 seconds but no sign of them settling down and don't want to leave them on any longer than that.
MR16 lamps are a nightmare, probably transformer incompatibility,& load on transformer, better to rip the lot out & replace with GU10 fittings & led lamps.
I would agree G5.3 12 volt are a problem getting bulb to match power supply, often the power supply is not a simple transformer but a switched mode power supply often called an electronic transformer, these change the output frequency into MHz range and since the bulb has a coil of wire in it that coil can cause a reaction to the supply frequency, also the units often have a minimum and well as maximum output. On the plus side they regulate the output voltage RMS valve which should make a quartz bulb last longer, but has no advantage with a LED bulb. With a GU10 230 volt fitting which is also MR16 with a quartz bulb all the control gear is built into bulb, the GZ10 will take the dichroic bulb which allows heat to travel through the reflector the GU10 with not and the GU10L2 has a dimple so will only take energy saving bulbs, so unlike the G5.3 type it will not allow you to fit the wrong bulb. With a LED bulb they are not technically MR16 as most LED's do not have multifaceted reflectors although still 16/8th of an inch across, but the reduction in how much of the 2" diameter is used, some of it being used for cooling fins can mean although the lumen is the same, the light seems less unless reflected off a white surface. 15 x 3W LED will light a room better than 10 x 5W even though the lumen is less with the 15 x 3W LED simply because the area of light emitting surface.
Sorry, yeah it's GU5.3 obviously, not 3.5. Ripping it out isn't an option at the moment as we have spent a fortune already. Sounds like we'll need to eventually. Realise this is a "how long is a piece of string" question but given I'm moderately clueless at electrical work, is the transformer likely to be accessible? Would an electrician always leave it accessible? Otherwise we're looking at lots of plastering work too.
As to transformer location you can never tell, had them were on removing light fitting, they are easily accessible, other times they are hidden away or fix to a joist & no chance in hell getting to them, unless you rip the ceiling down.
Yeah I thought that may be the answer. We'll just need to leave it for the moment then. Thanks to you all for the replies, really appreciate it.
Wow! didn't spot that, but it was early, must be a big attic, & rather warm & toasty with all that halogen heat.
The bulbs I took out (presumably halogen) refer to the 50w. I bought the only LEDs in the store which were the same fitting and their equivalent wattage was 35w. I think it was really around 4-5w. Does that make sense?
Ahh. That's the essential detail. The new (led) lamps are rated too low for the existing transformer. You would need to find the transformer/transformers and change them for LED drivers.
Don't connect the led's to the halogen transformers, they will work for a while and then fail. Good luck with finding the transformers.
GU 50w are halogen not LED. Ok here is some circuit theory... LED bulbs need a silicon driver and this driver incorporates a capacitance which charges to oscillate at a particular frequency to drive the LED. yes it oscillates at a very high frequency, so high you never percept it. If you mix bulbs the discharge of this driver circuit shorts through an incandescent bulb filament and causes it to flash at a noticeable rate. Do not mix bulbs, if you use LED make sure they are all LED.
hi, hijacking the thread here. I think I have the same issue, a halogen transformer behind a set of halogen GU 5.3 spotlights and I got some LED GU 5.3... The halogen ones seem to be dying, very little light left, and I got led ones. In a conjunct of 2 lamps, if i change one one of the halogen to one of the LED, the LED works fine. If i change both, they flicker. On a group of 7, when i change up to 5 to LED, the LED are ok, but if I change the 6th (and the 7th), they all flicker. If I understand right, the likely reason is a transformer mismatch and the ideal solution is to change it. However, I have no idea where the transformer is and how easy it will be to access and therefore change it. I just spent a budget on the house, so that Id rather postpone calling an electrician to do the proper job after some months or years if I can. Would it be ok to use a mix of LED and halogen? From what i understood here, it will lead to an early failure of the LED bulbs. Would that likely be very early like few months or last at least a year or more?
You can mix the halogen and LED. The output of the old transformer may cause issues with the LED, or it may not. You are going to have to find those transformers at some point. But there are so many gotchas if you keep the ELV (12v)/MR16 route and try and find a compatible driver…., Better to go 240v to the downlights and use GU10 bulbs.
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