Replaced old halogen transformer - lights noticeably dimmer

[winston1]

How have you measured the voltage?
Can you measure what the old one was supplying?

No - the old transformer was totally dead, says 12v on it.

New one I've not measured, it says 11.5v on it. Everyone seems to sell 11.4-11.6v ones now; 12v seems hard to find!?

Neither this nor the old one sound like transformers at all, but switch mode power supplies that operate at 10s of kHz with a non sinusoidal waveform. You are not going to be able to measure the RMS output voltage with the average multimeter.
If you really want 12volt output you are going to have to find a real wound transformer.

 

[Ben Lumley]

Know where I can get a 12v one? Even though advertised as 12, most places seem to sell ones that are stamped 11.4-11.6 on if you look in screenshots, including the replacement that's in at the moment. ... Starting to think I should force an LED conversion...

What sort of base do your 35W halogen lamps/bulbs have? Have you considered changing them to 40W or even 50W ones if they are available in your type?

Kind Regards, John

They are MR16, I had thought of this - but I assume they'd still be a bit yellowish, even if the overall light level is up? Might be wrong though...

 

[Ben Lumley]

The 12 volt one sounds like it may have been a "torroidal" transformer whereas the new ones are electronic ones, do you have a pic of the old one.

in the 90's the fashion was to use these and run each light back to it the lengths sometimes in excess of 3metres.

https://www.tlc-direct.co.uk/Products/TLT100slash2.html

it then became popular to use electronic and shove through the downlight hole, but there usually limited to 2metre sometimes less

The old one is like this - a big white/heavy box. Must have coils or something in. Maybe 8cm x 8cm x 18cm - something in that ballpark. A lot bigger than these modern ones. It does have windings as well (have another pic of inside)

 

[riveralt]

Thanks for your replies
Not switched to LED/Low wattage no - parents' house. I suggested it, they didn't want to in case they didn't like the light...!

Well do they like the current lights? If so leave them as they are now.

Starting to think I should force an LED conversion...

Best idea yet - save wasting time and effort trying to resolve what appears to be a subjective viewpoint of the light quality anyway.

 

[Ben Lumley]

Thanks everyone for replies.

For completeness - pretty sure it was this transformer I put in http://www.screwfix.com/p/robus-electronic-transformer-35-105va/92658 (if not, then another similar one on there)

Heard today that the light sometimes dims/flickers for a second every few seconds. Any thoughts on this? Assume it's an overheating thing - due to an overloaded or faulty transformer? Am I right in thinking that if the secondary wiring is too long + causing drop that it adds a bit of load on too?

Think when I'm next there I'll investigate the wiring - shorten it all up, single run to each light and maybe switch out the transformer, got another one ready for something else. Then see where we are.

 

[winston1]

Am I right in thinking that if the secondary wiring is too long + causing drop that it adds a bit of load on too?

No. Increasing the resistance in this way reduces the overall load. That is why they are dimmer.

Going back to the original transformer. These type rarely fail, I would be investigating why it had stopped working. Dry joint on one of the terminals perhaps. Internal fuse tired another possibility.

 

[bernardgreen]

It is almost certain that the Townsford unit was a wound transformer and not a switch mode power supply ( SMPS ) . If it was then its output would be smooth and without any high frequency ripple. The driver inside the LED lamp ( the device that controls the current through the LEDs ) will be a switched mode device and often feeding a switched mode device from an SMPS can end up with the two ripples interacting with each other, creating harmonics and other forms of unstable operation.

 

[Ben Lumley]

It is almost certain that the Townsford unit was a wound transformer and not a switch mode power supply ( SMPS ) . If it was then its output would be smooth and without any high frequency ripple. The driver inside the LED lamp ( the device that controls the current through the LEDs ) will be a switched mode device and often feeding a switched mode device from an SMPS can end up with the two ripples interacting with each other, creating harmonics and other forms of unstable operation.

It was wound yeap; the bulbs are halogen and not led though.

 

[Ben Lumley]

Am I right in thinking that if the secondary wiring is too long + causing drop that it adds a bit of load on too?

No. Increasing the resistance in this way reduces the overall load. That is why they are dimmer.

Going back to the original transformer. These type rarely fail, I would be investigating why it had stopped working. Dry joint on one of the terminals perhaps. Internal fuse tired another possibility.

Ah, that's another option, assuming it's not yet made it to the skip - thanks

 

[bernardgreen]

the bulbs are halogen and not led though

Ooops I should read things more carefully

 

[Ben Lumley]

the bulbs are halogen and not led though

Ooops I should read things more carefully

I learnt something anyway!

 

[ericmark]

The switch mode regulated power supplies often called electronic transformers were designed to keep the quartz envelope and tungsten element at exactly the right temperature. Too hot and the element burns out too cold and the tungsten is deposited on the quartz envelope. However the fact that the element is coiled and the frequency is high swapping make to make can some times result in the bulb not drawing the correct amount, but for it to be enough to cause a problem is rare.

With the old toroidal transformer the idea was to use a thicker element so extend the life, but there was no regulation of voltage. So a 200 VA transformer with 4 x 50W would have correct volts, but with 4 x 35W it could have a higher voltage than ideal.

Today the only reason for the transformer is where regulations require extra low voltage, the GU10 or GZ10 fitting will take tungsten, cold cathode, or LED lamps with non of the problems of ensuring the transformer matches the lamp. The use of LED also means less heat and no problems over heating beams and floor boards. Plus where used with pods one can actually move the lamp to light required area without burning ones fingers.

MR16 is really a redundant name. All the tungsten 2" lamps were MR16 be it 12 or 230 volt why 16/8" rather than simply 2" I don't know. But the cold cathode and LED replacements don't have the multi-faceted reflector so are not MR even though 16 x 1/8" so only tungsten lamps are MR16 the rest are just MR16 compatible.