Intermittent (but getting worse) problem with LV halogens on dimmers

[Dan Gravell]

I have four halogen LV downlighters in my kitchen, controlled by one dimmer switch. All of them use dimmer transformers. I once had to change the chocolate box on one of them that melted, but other than that they have given three years of trouble free operation.

Recently they have been failing to turn on. This affects all of the lights, not just one. I noticed that if I turned the dimmer down (made the light more dim) they would then come on, and turning the dimmer back up would turn them off again.

It's rather intermittent, sometimes they turn on fine at full power, other times not.

I took a look in the switch unit but all the connections seem fine there.

Any other ideas?

[TMC]

Replace dimmer with normal switch and see if they work OK

If so replace dimmer switch

Tony

[Dan Gravell]

Will do :)

[The Wanderer]

Have several 12v downlighters in my kitchen, two have been troublesome, not always coming on, though I don't use a dimmer. The bulb connectors have proved to be a bit problematical, I found the cables need to come out of the bulb connector more or less straight up. If the cables are bent at any sort of angle, the lights don't always come on. Very often, just the action of removing the bulb retaining ring from the fitting and easing the light down would make it light, then it would go out again when the bulb was secured back into the fitting.

I have a bungalow, and dressing the wires into a different position from the loft rather than trying to bend the wires from below through the fitting seems to have cured the problem

[Harry Bloomfield]

Most likely the lamp-holder to lamp connections. They run a lot of current and with a lot of heat. The lamp pins and lamp-holder connections tend to burn and become high resistance. Look at the lamp pins, they should be clean and polished, if not fit new lamp holders and lamp as a pair - they are not expensive.

[John]

You have a bad connection. You MUST fix it as it is a fire risk.

[John Rumm]

It sounds like you have several individual transformers - one for each lamp. Hence the only common point is the switch. So I would suspect that first.

[The Wanderer]

Err, no. That was the first thing I checked. 30+ years as an electrical engineer in power distribution has taught me where problems might lay.

What I didn't say, because I didn't think it necessary, I have a spare fitting and could do a simple jury rig on the bench to reproduce and study the problem when it first showed up. Poor design of the fitting maybe, as the contact is a single sprung strip down one side of the socket only. Bend the wires in the wrong direction and the contact is clear of the lamp pin; can't see it with the naked eye, but with the wires correctly positioned, the holder makes good contact with the lamp. Been fine with no overheating for a couple of years now.

[The Wanderer]

No, I have a poorly designed lamp connectors, which have now been operating perfectly satisfactorily for a couple of years since I first diagnosed the problem. See my reply to Harry Bloomfield.

Granny, eggs, suck, teach don't. Rearrange into a well-known saying! :-)

[The Natural Philosopher]

frankly, its nor clear what you have. separate dimmers and separate transformers, whether transformers are electronic of toroidal or indeed anything.

[John]

Poorly designed connections are giving you a bad connection - it still needs fixing even if you feel it is not your fault!

[The Wanderer]

You're beginning to annoy me.

They are fixed, by virtue of positioning the wires in such a manner that the contacts within the socket are now making good and proper connection with the pins on the lamps, and have been for a couple of years now.

Now be a good little boy and go out and play amongst the traffic.

[Dan Gravell]

Ok here's what I tried today. They've completely stopped working now.

I didn't explain this before but the dimmer switch is actually on a dual plate dimmer switch with another dimmer for another set of lights, which *do* work.

They are slightly different though. Both dimmers have three connections marked L1, L2 and another symbol which looks like a switch. On the working set all three are connected. On the faulty set, only L1 and the switch are connected, there appears to be no wire for L2.

Despite this, I decided to wire the faulty set into the dimmer switch used by the working set and just use L1 and the switch on the known-to- be-working dimmer.

This didn't work. The lights still don't come on. What would be a good next step?

As an aside, there also appears to be two wires bonded within an orange sleeve - I'm not sure if this is related to the 'missing' L2 wire on the faulty set.

Not sure if this was a reply to me or not... the faulty set has one switch, four lights, behind each one is a dimmer transformer. I don't know what toroidal means.

Thanks for your help!

Dan

[The Natural Philosopher]

The point is that inductive wound transformers break dimmers. Toroidal is a doughnut of iron wound as a transformer. Its less likely to hum than a standard Es and Is transformer. So its used.

HOWEVER there is enough leakage inductance to spike MANY dimmers.

electronic transformers may or may not dim successfully at all.

What you need is

- dimmers that are specified for inductive loads, generally 'suitable for LV lighting' OR

*electronic* transformers that are specified 'to *work with dimmers*'

Or face the consequences you have. Presumably triacs blown to shit, and either lights are on full all the time, or wont come on at all.

FIRST step is to say what exact dimmers and transformers you have.

The other possibility, and it happened here, is that you have a goofy track system, and the contacts to it are corroded up.

[Dan Gravell]

Thanks for your help.

The transformers are Aurora AU-E60 as seen here:

The info says "Fully dimmable with resistive and inductive dimmers"

The dimmer switch says the following on: GET BS EN60669-2-1

60-250W 200-240W 250W max

The lights are 50W I think, not sure if that causes a problem with the

60-250W statement above.

I have a photo of the switch, wired up, if it helps.

[John Rumm]

As long as the total combined load is in the range 60 to 250W you should be ok. Likewise each dimmer needs a load in the range 10 - 60W

[The Natural Philosopher]

OK so they are electronic dimmables. That's one thing out of the way.

Nope, as ling as a max of 4 auroras per dimmer is adhered to. 400W is better,but they should work

Now exactly how are they 'not working'

[Dan Gravell]

Well, now they simply don't light up at all when turned on at the switch. They went through this intermittent phase when sometimes they wouldn't light up when at the highest setting, and then for a while they worked if you turned them on at the switch (no light), left them for a while, and then the light would come on, but now - nothing.

What was it you were saying about the track?

[The Natural Philosopher]

Well I had some rather crap track lights, where the transformer plugged into the end.

The plug in bit corroded badly.

try the dimmers out on a meter or on an ordinary bulb.

[Mike Tomlinson]

In article , John writes

I have to agree. In the kitchen I have three lamps on flying wires plugged into a triple-way adapter at the transformer. Two lights are ok, the third was only coming on whenever it felt like it. Solid on/off. None of the typical flickering at all. Changed the lamp a couple of times with no effect.

Physical movement had no effect. In the end I swapped the misbehaving lamp with its neighbour at the 3-way socket - problem gone. The plug/sockets are very similar to the ones you see on PC power supplies at the motherboard end (Molex connectors).

It worries me a bit that the connections on those cheap Chinese made things can be so ephemeral.